cancer violence aggression obesity

stress if you want to fix all your

complex problems well this is

controversial but the vast majority of

the evidence suggests that Daniel

liberman a Harvard Professor who uses

the information of our evolutionary past

to understand the Health crisis we are

in today and educate people on how to

live a long healthy life the vast

majority of us in the Western World will

die from a mismatch disease chronic

stress that's what we call a mismatch

obesity heart disease many cancers are

mismatches and it's because we know live

in a world where we're able to have

incredible levels of comfort with all

this choice for example the number one

medical complaint is back pain because

I'm sitting in this comfortable chair I

don't have to use any of the back

muscles so we develop weak backs that

don't have any endurance we know that

people who sit a lot at work but then

also sit a lot in their Leisure Time run

way more risk of disease and if you

aren't Physically Active you don't grow

as much skeleton and then when you hit

25 to 30 for a rest of your life you're

going to start losing bone oh even in

this highly sanitized World we're much

more like ly to develop allergies and

various kinds of autoimmune diseases

because our immune systems are so

unchallenged they end up accidentally

attacking us also famous studies show

that the Richer the country the higher

the rate of cancer Bangladeshi women who

mov to England their cancer rates go way

up because of diet and physical activity

and stress things that have changed in

our modern world for which we are very

poorly adapted there's a lot to take in

is there an actionable conclusion that I

can do today that is going to reduce my

chances of getting one of these

mismatched diseases yes I think there's

two the first is

quick one this is really really

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[Music]

deal Daniel what is your job title I am

a professor of human evolutionary

biology at Harvard University and what

does that

mean it means I get to have a lot of fun

um I study uh well my department studies

how and why humans are the way we are

and we're also interested in how and why

that's relevant to to humans today uh my

particular specialty is I study the

human body I'm interested in how why the

human body is the way it is and how

that's relevant to health and disease

and I most interested most of my work is

on the evolution of human physical

activity but I'm also interested in in

diet and and and other ways in which we

use our bodies why does it matter well

because we weren't designed you know we

weren't engineered neared we evolved

right so if you understand why we are

the way we are you have to understand

that evolutionary history and and if you

want to solve problems if you want to

deal with you know big issues that we

face today obesity you know heart

disease cancer violence aggression all

of these things have an evolutionary

origin and an evolutionary origin is is

crucial to to helping us come up with

Solutions does what we eat play a role

in the sort of starting point of our

stories and how began to we I'm thinking

about farming Hunter Gathering um and

all those things because when I look at

human beings versus a lot of animals and

you talk about this in the book we Are

remarkably fragile in and inadequate in

comparison like our eyesight isn't that

great we're like super weak I think you

say that like most monkeys are stronger

than we are squirrels can run faster

than

us well I think we actually exaggerate

our fragileness and weakness to some

extent so so chimpanzees our closest

relatives um are about probably about 30

30% stronger than we are um you would

not want to arm wrestle a chimpanzee

right um and most quadrupeds um can run

way faster than we can right we are we

have this sort of story about human

evolution that it's been a sort of

Triumph of brains over braa right that

we have this we have tools and language

and and and that has enabled us to sort

of conquer you know the world and become

the dominant species and there's some

truth to that of course technology uh

language communication cooperation all

are essential part of the human success

story um but you know I think as

athletes we're pretty impressive we can

outrun most animals over long distances

so we're we're really impressive in

terms of endurance both men and women we

can throw we can kick we can do all

kinds of things that my dog can't do as

far as diet is concerned you know we're

we're the ultimate omnivores we can eat

anything um I mean most animals have

very kind of constrained diets there are

certain things they can eat most of the

things out there they cannot eat we've

managed to figure out because of of

Technology cooking food processing but

also because of the nature of our of our

digestive system we can eat just about

anything on the planet right people can

be vegans they can be you know they can

eat all meat diets they can you know

it's it's astonishing how much variety

humans can get by with um our you know

our livers can turn anything into

anything you can you can we can turn fat

into carbohydrates carbohydrates into

fat we have an incredibly astonishing

range of foods that we can consume when

we're thinking about our sort of

evolutionary history and and the hunter

gatherer tribes that still exist in the

world I think I've fallen into the Trap

of believing that all the answers we're

looking for about how to be healthy

humans in the modern world can be found

just by looking back at our hunter

gatherer

ancestors is that true that they hold

the answers to how to live a happy

healthy life well it's like everything

gets complicated right I mean to some

extent um we call that a Paleo fantasy

this idea that if you just go back to

being a hunter gatherer that you'll have

no problems right and that Hunter

gathers have no violence and they don't

get sick and you know all is well

well it's not so simple right I'll give

you one example murder we have this idea

that you know humans have become

incredibly violent since the origins of

farming right but if you actually look

at the ethnographic record Hunter

gathers are are just as violent as the

rest of us they're they're human beings

um they they they they kill for passion

they kill for greed they kill for uh you

know for that you know there's murder

there's there's Warfare among Hunter

gatherers even in in some parts of the

world yes it's true that hunter

gatherers don't have the same problems

with obesity they don't have metabolic

syndrome they don't have um they

probably don't get heart disease least

to the extent that we do there are

plenty of things that they do that are

worth um emulating but but they're not

role models in every respect and you

know what natural selection cares about

is how many offspring we have who

survive right that's the only thing

natural s cares out it's the equation of

life is food in babies out right that's

what that's what we're here for right as

far as natural selection is concerned

not happiness we're not here to be happy

we're not here to be nice we're not here

to be fulfilled or anything like that

although it's good when that happens

right we evolved to be hun gathers our

ancestors were hun gathers for millions

of years but those but the the

adaptations they have are primarily and

first and foremost about reproductive

success so we didn't evolve to eat foods

to make us healthy we evolved foods that

would increase our reproductive success

and we evolve to be healthy only to the

extent that Health promotes reproductive

success so you you can't just assume

that because our ancestors did something

it must it's it's optimal for health

it's you can it's more reasonable to

assume that that's optimal for

Reproductive success and remember it's

in those environments and in those

contexts and things have changed talking

there about what they one of the big

debates of I guess that's an ongoing

debate is whether we are evolved to eat

meet or we're meant you know we're meant

to be interesting use of words vegan an

or

vegetarians what's your perspective on

that cuz i' I've sat here with people um

who are really really passionate about

the fact that we're not supposed to

evolutionarily see how quickly I tried

to say that word because I don't know

how to say it um meant to eat meat well

that's just

nonsense I

mean humans have been humans started

eating meat about two and a half million

years ago there's no question at least

two and a half million years ago maybe

more and there was no question it played

an extremely important role in our

evolutionary history even chimpanzees

our closest Cousins eat meat

occasionally when they can they don't

get it very often uh maybe about less

than 5% of their diet is meat you know

from an evolutionary perspective we

evolved to have meat as part of our diet

but but of course you can be a human

being and not eat meat and do just fine

in fact there are some advantages

because remember we didn't evolve to be

healthy so just because our ancestors

ate meat or didn't eat meat doesn't mean

that's optimal for health today right

it's that's that's very sort of

impoverished way of thinking it's just

it's just illogical right um You our

ancestors didn't evolve to to to read so

should we not read reading is only a few

thousand years old right so it it

doesn't you know that's just not the

right way to think about about how to

use evolutionary theory and data the the

fact of the matter is that we evolved to

eat just about everything we are the

ultimate omnivores it's astonishing the

range of foods that we eat Hunter gather

is you know a typical Hunter Gather in

in the like for example there's data

from the Kalahari I think they eat about

uh like 800 different kinds of plants

many different kinds of animals right

and that's just the Kalahari humans

moved over the last you know few hundred

thousand years to pretty much every

corner of the planet and in every part

of the world they found foods to eat

humans live in the Arctic where there's

almost nothing but meat to eat in many

seasons and you know where you you get

plant food in the Arctic in the winter

by eating the contents of the intestines

of of the animals that they they they

hunt right

um and people evolved to live by by

oceans and and and fish and and die for

shellfish and you know eat shellfish I

mean it's that they live in in in

rainforests and eat bugs and you know

birds and monkeys I mean everywhere you

go on the planet people figured out to

eat various kinds of foods and one of

the ways we became so omnivorous is that

in addition to having incredibly

flexible digestive system we also have

technology to to Pro process our food so

by cooking our food by fermenting our

food by grinding cooking cutting it up

we've been able to essentially adapt

ourselves to an astonishing range of

environments hence an astonishing range

of foods and so so so now tell me like

what diet are we evolved to eat right

it's it's an impossible question to

answer is there a point in our history

where we learn how to hunt and gather

and was that the point where we started

really eating more Meats yes

so well first of all it probably wasn't

like a you know a a day you know you

know lightning bolt came down from the

sky and all of a sudden bam you know so

we we figured how to hunt U after all

our ape cousins uh will hunt when they

can but as soon as we became bipeds

which is probably around seven million

years ago walk on two feet right we we

became slow right you know chimpanzees

when they run can Gallop essentially on

four legs right and and that and they

can be really fast they can't run

distances but boy are they amazingly

fast and they can climb up trees like

like no human can around 7 million years

ago when we split from the chimpanzee

lineage it looks like we became you

know obligatory two-legged bipedal

creatures and as when you have only two

legs you can only run half as fast as

when you can have four legs it's like

having a cylinder car with half the

number of cylinders right you you know

you can just produce less power right

and so our early ancestors must have

been slow there's no way they could have

run that fast fast and certainly not

fast enough to be great hunters so I

suspect that compared to chimpanzees

they were probably poor Hunters because

they couldn't run down creatures the way

chimpanzees could right so probably for

a few million years meat was probably

rare in the diet but then we begin to

see starting around you know around

three million years ago maybe a little

bit older stone tools in the

archaeological record we find bones with

some cut marks on them and starting

around you know 2.5 2.6 million years

ago we have archaeological sites with

with bones of animals with cut marks on

them stone tools and those animals were

clearly butchered and by 2 million years

ago we have clear evidence that humans

were were were actually hunting you know

we have we have clear evidence that

these animals weren't just scavenged

they were definitely hunted so that

means that sometime between around three

and two million years ago hunting became

part of our ancestors repertoire they're

also making tools they must have been

cooperating uh they probably had some

form of communication or whatever we

don't know exactly what it's like and

they're probably eating a wide range of

foods including including what we call

extractive foraging so they're they're

eating tubers underground storage organs

right so instead of just plucking

berries off plants you know they're

they're actually finding high quality

foods that you have to dig for right

under the ground right it's like just

think about a potato it stores its

energy underground so there's a these

are rich sources of food but you have to

be able to dig for them and find them

right so this combination of extractive

foraging so not just not just plucking

leaves or berries off plants but finding

high quality resources hunting

cooperation tool making and Tool using

all together that's the hunter gatherer

way of life right and that emerged

sometime again between three and two

million years ago and that was

transformative that's the that's really

I think one of the most

important shifts that occurred in human

evolution and that's also incidentally

when we see this shift in our bodies

right when we when we going from being

more ESS more apik like australopiths

which had short legs and long arms and

they have small brains and you know

they're they're not Apes but they're but

they're more

apik to basically bodies that are more

or less like yours and mine so we have a

a fossil called uh the tur boy his real

name is naria kame he's from the west

side of Lake turana Northern Kenya he's

a homus uh who was probably about 8

years old when he died and you know from

the neck down he's basically like you

and me um his he's his his head is not

quite like ours but he's has a big brain

not as big as ours he has a doesn't have

a snout like a like a like an

australopith he's got a vertical face uh

he's got teeth that are basically like

yours and mine he's basically very you

know on that path towards being a human

and so hunting and Gathering and the

genus homo kind of come together and

that was I think one of the most

important major shifts that occurred in

our Evolution maybe the most important

actually more important than even the

evolution of our own species and that

allowed us to to become good hunter

gatherers so we have this nose that

sticks out of our face whereas like a

lot of our cousins look more like

Voldemort like they kind of have the

invert and that's a sign that of when we

became hunter gatherers right yeah so

that external nose right so a chimpanzee

has a flat nose like a dog right and

that external nose that you and I have

which is of course fantastic for holding

our glasses right well you don't have

glasses not yet at least um uh is um is

a oh we think it's a kind of a

humidifier so when air goes into our

nose it has to go through a little

nostril so it's a little what's called a

Venturi throat so it it goes through a

very narrow um bore and then into a a

larger space that has to turn a right

angle to get into the inside of our nose

and then has to turn another angle to

get down into our that pipe we call that

the FX that brings air to the down to

our lungs and all those twists and turns

and and changes in diameter cause the

air to be more turbulent so the air

instead of flowing in a kind of a you

know straight right um become it has

these V vortices it's it's got all kinds

of currents and when that happens that

means that the air has more contact with

the the the the mucous membranes in our

in our nasal cavity so it can pick up

moisture on the way in pick up heat on

the way in so our lungs are um don't get

dried out and on the way out it can

recapture that moisture so that we don't

um we don't lose that U moisture when

we're um when we're walking or for that

matter running so um if you on a really

cold day you can do a simple experiment

right when it's below freezing if you

breathe out right you see all that steam

coming out do the same thing breathe out

through your nose you'll see a lot less

Steam and that's evidence of this this

ability of our of our of our noses to

trap air um and that's because of this

external nose so so that happens around

2 million years ago or so um we can see

that cuz on the in the fossils we can

see the the margin of the nose and you

can see that it's lipped out it's what

we call inverted right it sticks out and

that's evidence that we had these

cartilages that sticked out suuck out

and and gave us our modern nose so so if

yeah if you went two million years ago

and you met an your your ancient

ancestors they would have had a nice

schn does what does this say about how

we breathe today because of there's been

a huge conversation I think over the

last couple years about breathing and

Bre breath exercises and mouth breathing

in particular um I've had people on this

show like James Nester who talks about

how there's a lot of disease happening

because we've kind of by habit become

mouth breathers when we

run um but also so many people seem to

be having a lot of problems with their

sleep my girlfriend for example she uses

nasal strips when she sleeps to try and

like open up her Airways and I she think

she's going to have to have an operation

but we've even got people in our team

that are seems like everyone's nose is

what do they call it when it's the theid

deviated septum deviated septum seems

like everyone's struggling with this at

the moment yeah I have to say I'm a

little skeptical of some of these

arguments the idea that you can fix all

your health problems by just breathing

through your nose um look breathing is

obviously very important but um but the

idea that for example when you run you

should only breathe out through your

nose that's just that's just silly um uh

that's just not true we evolve to

breathe out of our mouth when we run

we're the only species that does that

actually because it's an way to dump

heat when you're running you're

generating huge amounts of heat you have

to dump it or you're going to overheat

um and you you you breathe out through

your mouth for that reason right to to

kind of um to get the heat out of there

right breathing through your nose would

be maladaptive and no Elite runner on

the planet breathes out through their

nose when they're when they're running

um I'm not sure where that came from and

I just like to see more data to support

some of these arguments about nasal

breathing I'd like to see data to

support the the effectiveness of those

of those nasal strips uh sure breathing

is important there are better and worse

ways to breathe you know we're always

looking for Simple Solutions right to

complex problems and the idea that

somehow fixing your breathing is going

to prevent you from having a wide range

of diseases is um not true and people

who have sleep apnea which is a serious

issue um uh that's usually caused by

well it's caused by a variety of things

of course a deviated septum might be one

of them obesity can cause it there's a

number of other problems and of course

once that occurs um you know again you

want to treat the cause not the symptom

right so the best way to treat the cause

of the apnea is not to put a piece of

tape on your nose it's to it's to it's

to find the underlying cause by why

that's happening in the first place and

solve that and deal with that and

sweating sort of correlated to that turn

in the the fork in the road in our sort

of hunter gatherer history because

monkeys and even my dog Pablo he doesn't

seem to sweat from anywhere other than

his mouth I guess it seems like he's his

panting is his way exactly exactly so

the way in which most animals cool down

is by penting right they they breathe uh

through their mouth or their nose right

and there's there's uh air passes over

these mucus membranes on the on the in

the nose and the mouth and and and um

and what happens is that the air uh by

passing that air over the tongue or

whatever causes uh you get evapor

transpiration so evaporation so the air

the the the moisture in that goes from a

liquid to a gas phase right and that of

course costs energy so because energy is

because of conservation of energy that

means that for every I think milliliter

of oxy of of water that goes that goes

from wa water to gas I think it's 561

calories calories of the small CA and

that so that causes the tongue or the

surface of the nose to cool and then

there's blood right behind that blood

blood in the tongue thing if you cut

your tongue it's really bloody right if

you cut your nose right it's a lot of

blood there's a huge huge amount of

vasculature in there all these arteries

and veins right so that you cool then

the blood that's just below the surface

of the tongue and in the nose and then

that cools down your body right so

that's so panting is how animals cool or

you can even watch a lizard a lizzard

also does what's called G pumping it'll

it'll actually you know that's how it

cools itself down watch a a lizard will

run and then it'll it'll basically pent

and then it'll run again and it'll pant

and it'll run again because it's prevent

itself from overheating right now what

we did is we've we have uh sweat glands

so most animals have there's two kinds

of glands right there's one's called

aicon glands those are the glands we

have in our you know armpits and around

our genitals Etc or in our ears they

produce waxy sort of fatty substances

right there's the ones that smell or or

ear wax that protects our ear so all

most mammals have those aican glands

ecran glands are watery glands and most

mammals have them just on their palms

their paws and their feet right m so

that they can just think about when you

wet your finger you can turn a piece of

page right it gives you it gives you

more grip on something so when you're

trying to escape from a predator

sweating on your hands will help you run

up that

tree if you're a mouse or something like

that a rodent so most mammals have ecran

glands just on their palms but in

monkeys uh they started to evolve having

some sweat glands on their bodies but

not many and so chimpanzees monkeys have

some ecran glands on their bodies but

what we've done is we've increased that

by an order of magnitude we have like 10

times the number uh the 10 times the

density of Ean glands the monkeys and

chimpanzees and we lost our fur so and

of course fur prevents air

from from you from convection of air

next to the Skin So when you sweat on

your skin and you don't have fur the uh

you you can have evaporation of of

moisture and then and then air takes

that away quickly so you can keep

evaporating moisture and then you can

cool your body so we've effectively

turned our entire bodies into a tongue

essentially and so we can dump amazing

amounts of heat when we're physically

active in hot environments and that was

obviously important for ancestors uh

when they're hunting right we have a

huge Advantage In the Heat of the day

because we can not only we good at

running for All For You know because of

our legs and our muscles and Archilles

tendon and all these adaptations we have

for running but we also have this

incredible therm regulatory ability to

dump heat which the animal we're chasing

does not have and we can we can we can

they'll die of heat stroke but we don't

know when that happened and it's

possible that um that our stopi

ancestors before before hunting started

because remember they're two-legged

creatures right and they're not um

they're not very

fast so maybe in the middle of the day

when when it was really um you know hot

that was the best time for them to go

out and get food because that's the time

of day when carnivores that would love

to chase them right if I'm a carnivore

and I want to am I going to eat a

gazelle or an australopith right aopi is

going to be half the speed of the

gazelle that's easy pickings right so

I'm going to go for an australopith so

maybe our early ancestors forged in the

middle of the day when it was really hot

so that because they because they were

too slow to run away from carnivores and

maybe that was an adaptation and so the

ability to to to dump heat effectively

might have been really important for

them so it's possible we just don't know

that sweating actually came before

hunting it's just simply at this point

we don't because skin doesn't Preserve

in the fossil record we just don't yet

know when that happened what about a big

brain did that come before hunting or is

that a a product of the fact that we

started hunting it looks like more the

latter right

so are chimpanzees have brains you know

typical chimpanzee might have about a

400 cubic centimeter brain like 400

grams think about it in grams right

typical human has a brain that's like

1,400 gram so you know really like three

to four times the size of a chimpanzee's

brain for about five million years in

our evolutionary history so the earliest

hominins hominin is the term for

creature more closely related to us than

a chimp right so the earliest hominins

plus you know these australopiths like

Lucy they had brains that got up into

the 500 gram range rarely maybe

sometimes 600 but not that much

starting around two two million years

ago brain size just starts to shoot up

if you look on a graph right and that's

of course around the time we started

hunting but it's but it's really the

time we have hunting and Gathering and

so I think it's the whole system it's

it's not just meat although meat must

have been an important component of it

but the whole hunting and Gathering

system is really a way to get more

energy right because you're you're

you're processing your food so you're

getting more energy because you're

cooking your food or you're processing

it in various ways you're you're

cooperating you're you're you're you're

you're getting new sources of food such

as meat and Marrow and brains and

whatever all of that together means that

more energy is available and when more

energy is available then there's less of

a constraint on brain size because

brains are expensive just right now you

and I we're sitting right we're not

really doing much of anything other than

talking but one out of every five of our

breaths is to pay for our brain our

brain is using 20% of our metabolism

right and so to have a really big brain

means you have to have a lot of energy

available to you and so so most animals

can't afford big brains because they

don't have enough energy right with

hunting and Gathering you get more

energy more energy means selection can

now you know this the con the

constraints on having a big brain are

now released now you can get selection

for a larger brain so individuals with

bigger brains might have had some

advantage over individuals with smaller

brains maybe they were better at doing

this that or the other and so you get

selection for larger and larger brain

sizes and it really acceler Ates up

until you know well it continues up

until a few hundred thousand years ago

when essentially brains reached

basically modern size and then you get

fat because you have so much energy and

you have such a big brain it's it's all

about energy but that kind of makes

sense doesn't it you store more energy

and then we started to

get fat well fat is really important for

a number of reasons and one of them is

having a big brain so um you know a

human infant when it's born it's brain

is consuming half its metabolic energy

like when when a kid is born 50% of the

of the of the energy it's spending is

just to pay for its brain it's a brain

on a little body basically right and um

and of course you can't stop feeding a

brain brains require energy constantly

right brains don't store energy they

need a constant supply of glucose or or

Ketone bodies which you can use as when

you don't have sugar available to you

right you can get those from fats right

right so infants human infants are born

unusually fat guy named Chris kazawa

showed that you know we know that a

human baby when it's born is about 15%

body fat way more than any other species

right and that brain that all that fat

is really kind of an like money in the

bank to make sure that that brain always

has energy available to it and

furthermore he had published a really

cool paper a few years ago which showed

that when uh an infant's brain is

growing right in the first few years of

life the when it's growing really fast

that's when its body fat levels are

going down and when it's storing a lot

of fat that's when its brain isn't

growing very much so there's a tradeoff

in energy between fat and brains as

we're growing so so big brains and fat

bodies are intimately connected so we

want to make sure our babies are fat a

fat baby is an essential fundamental

human adaptation and and the body fat

that we have I mean a typical human has

much more body fat than than than than

most most animals most primates have

about four or 5% body fat most mammals

have about four or five% body fat

whereas a skinny human has maybe 10 to

25% body fat right so that body fat is

not only important for brains but it's

also important for our reproduction

because a typical mother nursing for

example right uh Hunter gathers will

nurse for about three years nursing is

really expensive it costs about 600

calories a day to produce breast

milk now imagine you're a hunter gather

and there's not a lot of food around

right you're in what we call negative

energy balance you're not getting as

much food in as you're spending right

you can't just stop nursing you're

infant is still going to require that

energy so you draw down on your fat

reserves right so having all that fat

which goes up and down and up and down

from season to season you store more fat

in the Good Seasons you use that up in

the Bad seasons those are fundamental

adaptations to keep us Physically Active

to enable us to reproduce the way we do

to pay for our big brains they're

they're part of you know that that you

know our our kind of relatively high

level of fat and our our predisposition

to store fat is fundamental to our

species we wouldn't be here if we if we

didn't have all that fat and I guess

this is why dieting is so hard right

because well we never evolved to diet we

evolved to put that fat on we did evolve

of course to use it when we needed it

right but we never evolved um to to to

get rid of fat it was just there was

never you know in an absence of obesity

there wouldn't be selection for for that

kind of physiological system to lose fat

without needing it because when we try

and diet it does feel like our body is

somewhat against us when I hear about

like sugar cravings and you know many

people have told me that if you the

reason why diets don't work is because

your body's trying to basically defend

the weight that you're at because that

used to mean your your survival that's

right um we call that a starvation

response right so when you go into

negative energy balance which is what a

diet is right you're spending more

energy than you're using and you're

taking in your body goes into a a

starvation response your cortisol levels

go up for example right it's a it's a

it's an emergency right it's like it's a

cortisol is our stress hormone stress

doesn't cause cortisol to go up cortisol

goes up when we are stressed and it

makes energy available to us and one of

the things that cortisol does is it

makes us hungry right when you're really

stressed at night right studying for an

exam of one of my students right they

get you know hunger you know they get

sugar Cravings right because they're

cortisol levels because they're stress

because I'm going to give them an

examine the next day goes up and then

they they want energy right cortisol

also makes you store fat in visceral

deposit so so so belly fat which is

which is you know concerning right it's

a it's a useful kind of fat right

because the fat that we store in and

around our abdomen is is very hormone

sensitive it's it's got lots of blood

vessels so that fat is a great energy

Supply when you're you know you're

physically active right when I when I

want run running around Central Park

this morning right I was burning some of

my belly fat but when cortisol levels go

up that's like it also directs us to B

deposit fat in those stores right and

the problem with those stores is that um

they're also very inflammatory so when

those fat cells get too large and they

swell they become

dysfunctional and they cause

inflammation they cause chronic systemic

inflammation which is just ruinous for

our health it causes diabetes and

Alzheimer's and you know heart disease

all kinds of diseases that um that

pretty much every major disease that

we're worried about the mismatch

diseases that we often talk about are

you know many of them are are stress are

inflammation related and and and and

that that's why we're con people are

concerned about excess uh adiposity

excess fat because excess fat causes

inflammation so that means that people

that are more stressed and more likely

to have belly fat correct yes that's

true so so that's one of the reasons why

stress is you know a risk factor for so

many diseases psychosocial stress is a

is a it has pernicious effects and

that's why you know racism

discrimination all those all those

factors that can Elevate stress

commuting um um have negative Health

consequences because it it causes us to

our cortisol levels to go up it causes

our us to us to put fat in the wrong

places it has a cortisol also turns your

immune system down

cortisol has all kinds of you know

negative effects when it's when it's

longterm and persistently

high it's often been said that if you

lose too much weight for example if a

woman loses too much weight then her

menstrual cycle will stop and I was

thinking about this from an evolutionary

perspective and you were saying how you

know fat is essentially evidence of our

survival so in some ways is that our if

that is true then is that our body

basically sto our menstrual cycle to

conserve energy basically if you could

think about it like our body saying to

us we don't have the energy to have kids

right now you are absolutely right so

it's a little bit comp more complicated

than that but but you you basically got

it right so there's two things first of

all fat is not just an energy store fat

is also an organ right fat fat produces

hormones we produce your fat produces a

hormone called leptin which affects

appetite but it also produces um

estrogen so so uh when women have very

low levels of body fat their estrogen

levels decline um and they don't produce

enough estrogen to have effective

menstrual cycles um so they become

what's called amenic am Menara is is a

is a just a fancy medical term for for

um U for loss of sort of normal cycling

it's been shown by many researchers a

former professor of mine Peter Ellison

and there other researchers around the

world a woman named GNA jensa and Poland

others have shown that you know our

bodies are Inc incredibly sensitive to

energy availability for example women

who are dieting they may have plenty of

body fat but when they're dieting which

means they're going to negative energy

balance levels of progesterone which is

a very important hormone for the

menstrual cycle progesterone is produced

in the second half of the menstrual

cycle and it maintains the the uterine

lining so you can have implantation

progesterone levels plummet they go down

by you know 50% during the ludal phase

that second half of the menstrual cycle

um thereby decreasing um their ability

to conceive um uh women who are very

Physically Active also there's a

decrease in the amount of progesterone

again during the second half of the

menstrual cycle a flip way of thinking

about it though is that because remember

what we evolved to do is to have as many

offspring as possible and so our bodies

also another way of thinking about this

also is that uh whenever there's extra

energy available the body you know it's

an adaptation to say hey let's use that

energy for reproduction so let's

increase estrogen levels let's increase

progesterone levels so we can increase

our our facundity increase our fertility

so there's a bit of a a balancing act

yes it's a bit of a balancing act so to

so obviously you know exercise is not

bad for women who are trying to conceive

and and and women who are but women who

are sedentary and aren't exercising have

high levels of Esten progesterone and

that may that's may be one of the

reasons why physical activity decreases

the risk of breast cancer so much so

women who are Physically Active have

like a 30 to 50% lower rate of breast

cancer and a lot of that part of that

has to do with the fact that their

hormone levels are more normal because

sedentary women have abnormally high

levels but nonetheless it's the the

important point from what you asked is

that our the body is incredibly

sensitive to energy right and so it

knows that when energy levels are low

when you're losing fat this is not a

good good time to invest because think

about it pregnancy lasts N9 months it's

incredibly expensive then you're going

to be spending months later nursing

which is also very expensive maybe this

is not a good time to invest let's wait

until times are better then you know

that this is a this is a better use of

your of your of you know a better time

to get pregnant a better you're can have

a much more likely positive outcome I

was thinking about what you were saying

through the lens of stress as well

because stress releases cortisol and if

someone is incredibly stressed I imagine

they're going to have trouble with

fertility as well probably for the same

reason I guess it's like a line was

running at you this is not a good time

to have it cortisol cortisol one of the

things that cortisol does is it turns

down everything that you don't need to

do at that moment in time right because

we evolve to elevate cortisol acutely

you know for short bursts when you know

when when the lion comes into the room

right um but but not over very very long

periods of time so you know when when

when the lion comes into the this is not

a time to reproduce it's not a time to

spend energy on your immune system it's

not a time to do all kinds of stuff

right just run right make energy

available but situations where you have

persistently high levels of cortisol

chronic stress chronic stress that's

what we call a mismatch right mismatches

are conditions that um for which our

bodies did not evolve right these are

novel environmental conditions um for

which we are inadequately or imperfectly

adapted for and that they cause the vast

maj majority of the diseases and

problems that we we encounter today and

you know taking exams is is a mismatch

um having you know you know

discrimination racism poverty um these

are you know any all those sorts of

things that elevate our cortisol levels

for long periods of time those are

mismatches you know in fact the vast

majority of the diseases that people

have today um apart from some infectious

diseases but the vast majority even of

infectious diseases are mismatches

because they come from humans spending

more time with animals and like all all

the a lot of the diseases that we you

know infectious diseases that we have

actually are diseases that jumped over

from the animal world to to humans

tuberculosis for example right that's a

disease that Hunter gathers didn't get

it's a it it came after farming the vast

majority of diseases I would say so yeah

I mean heart disease I mean look we when

we look around the world and look at

people who don't live in you know modern

Western Lifestyles they they heart

diseas is is rare to non existent

there's a wonderful study of a of a

group of people in the am in Amazon

called the

chiman there these are horticulturalist

foragers right they have there's like no

evidence whatsoever of any coronary

heart disease in these people some of

the populations that we've studied no no

increase in blood pressure in fact back

in the 1970s some of the first studies

that were ever done on the health of

Hunter gathers found that 80-year-old

hunter gatherers in the Kalahari had the

same blood pressure as 20-year-old

hunter gatherers in the Kalahari where

and they compared them to to to to to

English um people and you know londoners

at the same time and of course by the

time you're 70 or 80 in London almost

everybody's hypertensive right this is

this is a this is because of diet and

physical activity and and probably also

stress um these are these are these are

things that have changed in our modern

world for which we are very poorly

adapted no

diabetes if it exists nobody's diagnosed

it it's probably incred rare but even a

few Generations ago diabetes was rare I

mean diabetes is the world's fastest

growing disease where I work in Kenya um

in in the area around the town city

called

eldoret when I first started working

there gosh long time ago you know you

drive into the city then you'd be an

eldoret now as you drive into the city

you pass by all these diabetes clinics

they they weren't there before that's

because diabetes is rising in in in

Africa

to at incredibly rapid

rates which you know isn't that

surprising because diabetes in places

like the United States and England are

incredibly common about something like

12% of Americans have diabetes now you

said that this mismatch is responsible

for most diseases doesn't that therefore

mean that I'm most likely to die from a

mismatch disease in my life yes okay yes

the vast majority of us in in the

Western World will die from a mismatch

disease the number one disease in the

world today that kills more people than

anybody anything else is is heart

disease and as far as we're you know

heart diseas is kills at least about a

third of us cancer is number two cancers

of course are ancient disease so not all

cancers are mismatched disease but many

cancers are mismatches right breast

cancer which is much more common in

Western populations than in non-western

populations um but heart disease you

know is essentially as far as we're

concerned non-existent until fairly

recently and now it's killing about 33%

of us 30 you said a third right yes

that's crazy so so crazy that's the bad

news right but the good news is because

they're mismatch diseases they're not

they're not inevitable right we

shouldn't just say all right heart

disease kills a third of us let's just

um because the the amazing thing about

heart disease is that diet and exercise

can prevent a large percentage if not

almost the almost all of them right if

people who live in environments where

they don't eat obesogenic diets diets

that are that make people overweight

diets that lead to metabolic syndrome

diets that are uh that are atherogenic

that cause a atherosclerosis right

people who are Physically Active um and

stress is also an important role plays a

role in heart disease don't smoke um

have vastly lower rates of heart disease

to the extent that it's you know this is

a this is a this is a disease that

doesn't have to exist you said you're

writing a book about diet and food yes

why the story of how the diets that we

eat today and and uh is is actually a

really fascinating story but also um

because I think that we um if we take a

more evolutionary approach to diet um we

can I think do much better to thinking

about you know help people make choices

I mean one important point to make is

that you know today like when we finish

this interview I'm going to go home and

my wife and I are going to and my

daughter and my mother-in-law are going

to try to decide what we're going to

have for dinner tonight right and we can

like we can go we can eat whatever we

want right we can go to the supermarket

and there's like you name it right here

in New York the really is you name it

right we can we can go out to

restaurants we can have Chinese or food

or Japanese food or American food or

French food whatever right we have we

have incredible choices to us for most

of human evolution history people never

chose what they ate ever right they ate

what was available to them and now with

all this choice we comes comes comes bad

choices right and so uh I would like to

help people figure out how not only

realize that these choices that we have

to make are we're not really evolved to

do but also how to better understand

what those choices are and what the

complexities are of of them because

there are no there there's no such thing

as a free lunch right every every choice

that you make has Alternatives and

alternative consequences and and I think

people oversimplified diet people come

up with simple ideas how you know just

do this just be a vegan just be a this

just be a that um there are no perfect

answers do you think in some ways that

our culture moved so much faster than

our biology in a sense because we're

like super sedentary now we just sit all

day we have these screens that bring us

our food um the food is processed and is

this part of what's causing this sort of

misalignment all these Mis mismatch

diseases as you call them is absolutely

because evolution by natural selection

occurs really slowly right every

generation people with genes that have

given them adaptations they're better

able to handle a particular

environmental context do better than the

Next Generation so slowly slowly

slowly Generation by generation you get

change right and that's true for every

animal right um mismatch is not unique

to humans right as environments change

some animals are better adapted to that

environment than other animals and

though those animals are going to be

more likely to pass those genes onto

their offspring so mismatches are part

of a natural selection every species as

environments change is subject to

mismatch or as they move into new

environments the difference with humans

is that we have culture and culture has

caused an acceleration of environmental

change right think about I mean just

today right I have now a in my pocket a

a computer right that I didn't have a

few you know decades a AG go right um we

have internet and email and all kinds of

things right just the last few decades

the world has changed amazingly just

think about the last few Generations the

last few hundred years the last few

thousand years so cultural evolution is

so powerful and so rapid it's so fast

it's so transformative that we have made

our world so F vastly and rapidly

different that our bodies cannot

possibly keep up in terms of our biology

it's this mismatch it's this difference

between evolutionary biological change

and cultural change that has heightened

the kinds of mismatches that we exist

and then guess what we do right so we

let's say we I'll give a very simple

example right until recently nobody read

right and nobody spent a lot of time

indoors and so myopia used to be

extremely unusual right what's that

myopia is having is being nearsighted

okay so if you go to like there's a

famous study where they looked in in in

Inuit populations right in Alaska and

they looked at grandparents and

grandchildren the grandparents all had

perfect vision and the grandchildren all

need glasses or at least a large

percentage of like 30% of them right in

various parts of the world the the

number of people who are are nearsighted

has gone up in some parts of the world

it's 50% and in America and England it's

probably about 30% of us need glasses

but this is all recent um the in fact

the first study of this was done on the

Queen's guards you know the actually now

they're the king's guards right so you

know those those they have the bare skin

hats I don't know what kind of fur it is

on their head anyway they're the ones

who stand in front of imp Palace right

there was a study done in the in the

early 1800s which showed that um it was

the officers who had a higher percentage

like a large number of the officers had

to wear glasses but the the the foot

soldiers were all fine um and there was

something about it right that that about

the officers and then people started

studying them around the world and and

then initially it was thought to be

reading and now we know from more

careful studies is that's really

spending a lot of time indoors when

you're young that causes myopia so we

never evolved to do that right so we're

more prone to myopia but it's not a big

deal because guess what we just go to

the optician and we get glasses and we

can deal with it and you know it's not

doesn't really have really any major

effect on our on our on our health or

our longevity our ability to find a mate

Etc we all do just fine can we undo it

well here's the thing I mean we're what

we're doing in no myopia you you can get

lasic surgery and there are some things

you can do very expensive most people

can't afford it right but the point is

that we're treating the symt with when

you get glasses you're treating the

symptom not the Cause right but it's

okay right because it's just glasses

right the problem is that for many

mismatch diseases right when we are

still we're treating the symptoms rather

than the causes right so cancer cancer

right or or or many forms of heart

disease right you don't see a doctor in

our in our in our medical system until

you get sick right and then you get

pills to lower your blood pressure and

pills to lower your cholesterol Etc but

but these aren't well those some of them

can be preventative but but um but to a

large extent most of Medical Treatments

are treating the symptoms diseases after

they occur and I'm of course we should

do that we should alleviate pain we

should alleviate suffering we should try

to decrease people from you know dying

from all kinds of diseases but wouldn't

it be better if we actually prevented

those diseases in the first place right

we would have a much more effective

medical system so what we're causing in

my opinion kind of a new form of

evolution I call this dis Evolution

where by we're treating the symptoms of

mismatch diseases thereby enabling those

diseases to remain prevalent right and

if some cases get worse because because

we can now cope with them right so

people now get diabetes we give them

metformin or whatever various kinds of

drugs they get they get heart disease we

give them various you you know pills to

kind of keep them going they get myopia

we give them

glasses all of these are are are are

things we should do but wouldn't it be

better if we prevented people from

getting heart disease in the first place

right because this is one of the big

questions I always have with Evolution

and when we're talking about our

evolutionary history is is are we still

evolving and from what you said there it

sounds like we in a way we are but it

doesn't sound good it sounds as you say

de Evolution sounds like we're in some

ways disolution disolution yeah I mean I

mean there is there is a little bit of

selection going on I mean you can't stop

s it's like gravity it happens but it's

slow what we eat and how we eat um I

think it was James Nester that said the

way we chew impacts what our face looks

like when we become adults if a baby's

chewing lots of soft foods when they

grow up they're going to have like a

small jaw yeah that's research I did

actually oh really I think you cited

you um yeah so so how you your chewing

affects the the shape of your you know

how your your jaw grows um and so it is

true that we have smaller Jaws today

than we used to the good news is it's

not that bad right doesn't really cause

that much you maybe your teeth are more

likely to have malocclusions Etc but you

know you can but we can go to the

orthodontist and have our third MERS

extracted Etc I mean we can we can cope

with that right it's not um it's that's

not the worst thing right of course he

thinks that it causes us to breathe

through our mouths and all that sort of

stuff but it's not the kind of

disastrous sort of um mismatch that

occurs from say you know uh well this is

controversial but um the evidence you

know the vast majority of the evidence

suggests that if you eat a lot of sugar

and you eat a lot of saturated fat

you're more likely to get heart disease

you're more likely to get plaques in

your arteries right if you don't aren't

Physically Active you're you know do

exercise or or physical activity your

your blood vessels start stiffening and

you start becoming hypertensive right uh

these are all um these are all aspects

of our environment that um that we we

have the potential to to to control

better and to prevent disease do you

think we've got into a bit of a bad

habit as a society of just throwing a

pill at the problem yes I mean that's

that's the fundamental argue argument of

making about dis Evolution that that you

know it's just it's expedient to treat

the symptoms of a problem rather than

its cause what's the problem with that

well

because number of reasons one is it's

isn't the the best disease is the one

that you never get in the first place so

so we can keep people alive once they

get heart disease we can keep people

alive once they get arthritis we can

keep people alive once they get all

kinds of diseases but they but their but

their quality of life goes down and of

course we pay for it we pay for it out

the nose right it's something like 70

80% of the time when somebody goes into

a doctor's office that's for a

preventable disease 70 80% of the time

right that's a an astonishing amount of

money that we spend in our medical

system on essentially mismatch diseases

it's bankrupting us but it's also

causing misery and

um it differentially affects people of

of low income and people who are of

suffer from

discrimination um I mean look in the

United States right who gets the chance

to exercise and eat you know fresh

vegetables and you know high quality

foods and nonprocessed Foods it's it's

wealthy people right so it's also it's

just unfair and unjust you mentioned

cancer and in what way and how do we

know if that's a mismatch disease well

cancer is not completely a mismatch

disease I mean you know all species that

are multicellular get cancer cancer is a

is essentially a disease of evolution

going wrong right natural selection

going wrong right so instead of you know

when you have many different kinds of

cells in your body when a cell becomes

essentially selfish and starts to

outcompete other cells because of

mutations it gets that's a cancer right

so cancer is an outcome of

multicellularity and dinosaurs got

cancer right we have evidence for bone

cancer and dinosaurs

um so it's we're never going to get rid

of cancer

completely but we also know that cancer

is very much a disease of energy right

when when people move to high energy

environments they're much more likely to

get cancer more food eating more more

food physical inactivity is a major risk

factor for cancer um insulin for example

high levels of insulin insulin you know

promotes um you know anything that

promotes mitogenesis you know which is

mutation you know cells to divide um um

is going to increase rates of cancer um

also anything that increases the rate of

of U you know a lot of the cells that

get cancer are cells in our bodies that

interact with the outside world so our

lungs our guts you know our colons or

you know things from the outside world

come into contact with them skin exactly

those are cells that often get cancer so

when we have carcinus you know poisonous

toxic compounds in our environment those

can Elevate levels of canc cancer so

smoking car pollution etc those can

cause cancer but also having lots of

energy so we talked earlier about when

women are physically inactive their

their their hormone levels shoot up

right because the body says ha more

energy let's spend it on reproduction

right and there's a trade-off there more

the higher levels of estrogen

progesterone increase the rate of of

breast cancers that that

occur because because they cause more

more turnover in those cells in the in

breast tissue and that's that's why the

those cancer rates are higher so you can

there's famous studies which show that

you look at women from Bangladesh who

live in Bangladesh women from Bangladesh

who moov to England or Bangladeshi women

who are born in England and live in

England wherever you no matter how you

how you look at it Bangladeshi women who

moved to England their cancer rates go

way up the difference a major difference

is energy you know the diet that they

have the physical activity levels they

have they're eating more they put more

we cancer rates just shoot up canc so if

you actually plot GDP of countries

against cancer rates it's almost nearly

straight

line the Richer the country the higher

the rate of cancer what about hunter

gatherer women did they have less um

ovarian cancer o that's a hard thing to

measure because diagnosing cancer

requires some sophisticated technology

and to my knowledge nobody's ever done

careful studies of cancer rates among

Hunter gathers um but most of us are

pretty convinced that cancer rates are

much much much lower among Hunter

gathers but again also the the

population sizes are tiny so you can't

really get very large samples the amount

of menstrual cycles you have is major

factor right so I believe hope I get the

numbers right typical woman today who

goes through her entire reproductive

lifespan will have something like 500

menstrual cycles because of birth

control and um um and smaller families

it says 350 to 400 in your book is that

what it says okay thank you okay um it's

a it's it's in the hundreds right

typical Hunter gather is going to have

something like 50 50 yeah in her entire

life Wow and every time you go through a

menstrual cycle your your body is being

exposed to high levels of these hormones

right birth control um and sort of

Modern Family Planning which you know

I'm not obviously

um opposed to it but it is another

factor that has probably elevated rates

of breast cancer I didn't I never knew

that I never knew that having more

Cycles reduced your sure because each

every cycle involves you know surges of

hormones that's what causes the

cycle first you have an estrogen surge

then you have a progesterone and an

estrogen surge of course that's that's

what happens across the menstrual cycle

and hunter gatherer women would have

been pregnant more often more of their

life well yeah they a typical what we

call a natural fertility population a

population that doesn't use birth

control women are most of the time

pregnant or nursing and they go through

short periods when they um are doing

neither and then get pregnant again so

so the number of and and you don't of

course have menstrual cycles when you're

pregnant and you're generally don't have

menual Cycles when you're nursing until

again it's your energy level so so

because nursing costs so much energy

that high energy demand of nursing

suppresses ovarian function so and so so

so nursing women are often amoric

they're not cycling and that's not just

ovarian cancer that's breast cancer as

well that's yeah it's you know you any

any any cells that are sensitive to

estrogen and progesterone those those

are the cancer those those particular

kinds of so often when you you you you U

measure breast cancer you talk about you

know whether the the cells are estrogen

or progesterone sensitive I wanted to

talk about how our body stores energy

because I think that in part uh answers

a lot of these questions around around

um the things we're discussing about

weight loss about diet about all those

things we've talked about previously I

have a very loose understanding of this

so please enlighten me but I did go keto

for eight weeks and I lost so much

weight it's pretty crazy it bounce

straight back of course of course

because you're mostly lost water oh

really yeah that's one of the problems

with many diets so so fat is a is a fat

is a wonderful molecule right it's we we

tend to demonize it but it's fat is life

right fat is a really important molecule

so a fat is a is a a fat molecule has a

backbone of something called glycerol

glycerin right it's a three carbon

molecule there's a carbon carbon carbon

and there they little hydrogen sticking

off and to each one of those carbons is

a chain it sticks off a chain what's

called a fatty acid so so they're called

Tri glycerides they're Three fatty acids

on each glycerin and and there are

different kinds of fat fatty acids like

they're saturated fatty acids and

unsaturated fatty acids we can talk

about all those whatever but the point

is that these are each fatty acid stores

a huge amount of energy because those

long chains of carbon what our body does

is it Cleaves those carbons into smaller

units and gets and we get energy from

the from the bonds between those carbons

that's basically what our mitochondria

are doing right so fatty acids fats in

general have store a huge amount of

energy they store twice as much energy

as carbohydrates per unit Mass

so what we do is we we eat foods that

have fat in them or we eat carbohydrates

and our livers convert them quickly to

fats it's not it's it's easy right so

that's why you know fat-free diets don't

prevent people from being fat right

often with the help of insulin but it's

not the only hormone involved we then we

want to store those if you're not

burning them right our body can either

burn them or store them so if we're not

burning them I you we're running or

gesticulating talking Etc um um we we're

going to store them and we store them in

in special cells called adipocytes those

are the fat storing cells and our bodies

have billions of them you're born with

billions of these but you only have so

many adipocytes you get them when you're

young when you're born and that's it

that's the number of adipocytes you have

for the rest of your life and so and so

those adipocytes so insulin for example

helps potentiate the movement of

triglycerides

right which which you want to break down

and then you transport them into the fat

cell C and then you reassemble those

fats in the fat cell the glycerin and

the fatty acids you reassemble them in

the fat cell and they swell like a

balloon so every little fat cell in your

body is like a little balloon filled

with with fat and um and it's there to

be used and then there are hormones

which then help us retrieve that fat

when we need it right when we're running

a marathon or or just sitting around

talking and without having had lunch for

a while or whatever um and so you know

we we store fat we we then burn fat we

store fat we burn fat we store fat we

burn fat Etc and that's normal right and

as I as we talked about earlier in this

conversation humans evolved to have an

unusually high level of fat so a typical

Hunter gather male will have about 10 to

15% body fat typical Hunter female will

have about 15 to 25% body fat that's

normal sort of skinny human being that's

way more than most mammals right so

women had more women have more right so

women have a higher uh uh percentage of

body fat although actually women tend to

be smaller bodied so the total amount of

fat that men and women store is about

the same women of course if you think

about it um because they're involved in

they're the ones who have to pay for

reproduction directly either during

pregnancy or or nursing that fat is

especially important for reproduction

right so what happens is that that fat

is there and it's like a banket count

right it's energy that we store and

energy that we use and we store it in

different places most of the fat that we

store stores what we call subcutaneous

so underneath the skin

subcutaneous but we also store fat that

we call ectopic that's outside of where

it should be some of that fat is a lot

of that that ectopic fat is some of

that's in our liver we call that um so

people have a lot of so normal livers

have just a little bit of fat in them

but if you have too much fat in your

liver your liver starts to malfunction

it's called non-alcoholic fatty liver

syndrome you can have fat around your

kidneys that's what seid is right but

too much fat around your kidneys again

causes problems fatter around your heart

fatter around so any all that fat in

your in your in your abdomen that we

call that visceral fat viscera means

guts right so that gut fat is is is very

problematic and all because when those

fat cells get too big so if you store a

lot of fat Beyond those sort of normal

levels as the fat cells get bigger and

bigger and bigger just like any balloon

they start to

rupture so you know if you overfill a

water balloon it's going to break if you

overfill an hosy it's also going to

start break and when it starts to break

it attracts the immune system and the

immune system comes in white blood cells

come right they're they're they think

something's wrong you have a we have we

have damage here and they start to

produce

molecules that

trigger a a systemwide immune response

right and this and the fat cells

themselves also will trigger an immune

response the fat cells can produce the

same kinds of molecules that are white

blood cells produce so the white blood

cells are produce molecules called

cytokines cyto for cell right Kine for

you know enzymes that do something right

and and so the ones that fat cells

produce we call them

adipokines and like one adipokine that

produce is called is a TGF Alpha right

you may have heard of and that turns on

your it's like a it's like turns up the

dial on your on your on your

inflammatory system right and it goes

everywhere in your body and you start

getting inflammation right and that

inflammation for example if it's those

turn if if you have inflammation in your

your blood vessels then that

inflammation can help cause plaques to

form in your arteries if that

inflammation occurs in your brain those

can cause plaques in your brain that can

cause Alzheimer's if that inflammation

affects um uh receptor cells on muscles

Etc that can cause insulin resistance

which can cause diabetes and and the

list goes on right so that that chronic

inflammation which can be caused by too

many fat cells that are

overpacked essentially is is why too

much fat uh can can be can cause health

problems the keto diet and fasting they

someone said to me the other day that

keto is basically a form of fasting in a

way um and are they how do they help the

body because people are pretty crazy and

pretty keen on both fasting at the

moment but also the ketogenic diet well

fasting is when you go into negative

energy balance right which is how we

spent most of our sort of evolutionary

history right well you how you spend

part of every day right we we

eat after you eat you're in positive

energy balance and then when you in

between meals your energy balance goes

down right now you're a neg you're

burning now energy that you've stored

when you're asleep you're a negative

energy balance so fasting is just a

prolonged state of negative energy

balance right does that mean that it

would reduce my chance of getting cancer

could do people are are hoping that's

the case I don't know how good the data

are for intermittent fasting um because

if the Surplus and energy causes cancer

then me being in that negative energy

balance presumably will reduce my

chances of getting these right but then

you have to go back into positive energy

balance at some point too right you

can't keep up negative energy balance so

intermittent fasting isn't necessarily a

way to lose weight if you

eventually you know replace those

calories right so what you so here's a

hypothesis right to which I cannot um I

cannot prove but I think that you know

when you when you exercise right you're

also going to Nega negative energy

balance because you're burning energy

you're not eating while you're exercise

least most people aren't right and and

your and your body's turn you know

turning on all kinds of mechanisms to to

um to cope with that negative en energy

balance you're turning on all kinds of

repair and maintenance mechanisms when

you when you when you're go through

intermittent fasting you're basically

doing the same thing but less acutely

it's it's a more gradual level and I and

if you look at the at the at the genes

that are turned on by exercise and the

genes that are turned on by intermittent

fasting many of them are the very much

the same and I think it's because you're

basically turning on genes that are

responding to that negative energy

balance um but um but I would argue that

you're going to get more of a bang for

your buck by exercising than just going

through intermittent fasting both well a

bit too much yeah I mean intermittent

fasting might be a kind of a easy way to

get some of the bit bits of exercise

without exercising it might be I mean

obviously we went we you know there's

nothing necessarily wrong with

intermittent fasting but I'm not sure

that it has some of the huge benefits

that people claim now keto diets are a

little different right so keto diets are

when you're you're basically avoiding

any

carbohydrates and carbohydrates the the

basic building block of most sugars is

is glucose right glucose is the sort of

a simple form of sugar that are

basically in starches there there's some

other sugars fructos is also which which

is the kind of the sweet one but when

you basically stop taking in glucose

right you're now basically taking in

only fats and and so instead of using

glucose to fuel your brain and and other

cells in your body You're Now using

what's called Ketone bodies these are

these are essentially remember we talked

about how you when you break those fats

down into small little units those are

Ketone bodies U they um they can be used

as energy but um they're more of a kind

of a backup energy source for our bodies

than than the primary energy source so

we we use them um we T our bodies tend

to use them when we don't have glucose

available to us and does that mean the

same sort of repair and restore

mechanism kicks in potentially no I

don't think so because that's not

negative energy balance you're just

using an alternative fuel in this

particular point because a lot of

doctors have sort of prescribed a keto

diet for people that have like epileptic

seizures right and I don't think anybody

knows I'm not a neurologist but I don't

think anybody knows

why High Ketone diets are so

beneficial for epilepsy but it could be

that they do and I just don't know and

I'm that's not my it's not my subject

but anyway there's a there's a there's a

thought that if you just you know

essentially keep your insulin levels low

and rely on Ketone bodies instead of

glucose you can you know do all kinds of

miraculous things um for weight loss if

you look at the data yes it does tend to

uh lead to Rapid short-term weight loss

but the data don't s don't show it is

very effective as a a long-term weight

loss strategy and I think your your

example your own anecdotal account is is

sort of typical are we too coddled are

we cuddling our kids too much and

cuddling ourselves too much and is that

causing some of these mismatch

diseases well I'm not a psychiatrist or

a psychologist so uh physically cuddled

oh physically cuddled um stopping kids

from doing anything that might hurt them

or you know the risk aversion and yeah I

think so yeah I mean the Comfort

industry absolutely I mean you know I

have a whole chapter in my book on

Comfort right we have this idea that

Comfort is somehow good for you like

where does that come from right um

comfort is nice but you know I mean who

wouldn't rather be in business class

than in economy right but um but uh is a

comfortable shoe better for you right is

like is sitting in a chair better for

you than walking around or standing is

it better to take the stairs or take the

lift or the elevator um so Comfort isn't

necessarily good for us but when we but

we now want to live in a world where

we're able to have incredible levels of

comfort and um and it's definitely not

doing us some good because you know kids

need to run around I mean every kid

needs a good hour of physical activity a

day to build a healthy skeletal system

and to you know for for all the other

benefits that come from physical

activity so preventing our kids from

running around and doing physical

activity is definitely a problem is

there any evidence that our kids are

getting sort of physically weaker or

physically oh absolutely absolutely I

mean we have data in the United States I

mean we have this thing called the

Presidential Fitness Test right that was

started I think maybe it was Kennedy

started I can't some president a long

time ago

so we have decades worth of data and

kids today are are are less fit

absolutely uh any ask any army recruiter

they'll tell you that fewer and fewer

Army recruits are are physically fit and

able to be what about strong in terms of

Bones and our skeletal structures yeah I

mean the rates of osteoporosis are going