WHY DO WOMEN

NEED FAT?

Will Lassek

Look here first

Who is the most attractive

imaginary woman?eg. animated films,

video games,comics, graphic novels

Jessica Rabbit“most attractive

imaginary woman”

650 undergradsof Steve Gaulin“sexiest cartoon

character”Cadbury contest

What is hermost

unusualattribute?

Jessica Rabbit

Waist/Hip Ratio: 38%

Waist/HeightRatio: 15%(10 inches)

38% 68% 74%

Playmate undergrad

WAIST/HIP

15% 10 in

36%24 in

44%28 in

Playmate undergrad

WAIST/HEIGHT

WHERE DOMEN LOOK

FIRST &LONGEST?

Cornellisen, et al. 2009

eye tracking:WAIST is

where men look first and most when judging attractiveness

Look here first

Why should we care what menfind attractive?

Look here first

Men should admire qualitiesthat help women havechildren that survive

HOW IS WOMEN’SWAIST FAT

CONNECTEDTO HAVING CHILDREN?

14161820222426283032

20 22 24 26 28 30 32 34 36Waist, inches

BM

IWaist & BMI (Body Mass Index)

small waistrequires low BMI

correlation = 0.93

Playmatesundergrads

Jessica’s BMI?

Jessica Rabbit

waist/height15%

predictedBMI:

10(from waist, hip, height)

Average weight of young US women by BMI

90

100

110

120

130

140

150

16 17 18 19 20 21 22 23 24 25

BMI

Pou

nds

BMI <20<120 pounds

Men prefer women with low BMI’s Martin Tovee, et al. 1999

attractivenessscores

0

10

20

30

40

50

14 15 16 17 18 19

BMI

Per

cent

Cumulative BMI % age 18-20, 1971-75(before the obesity epidemic)

half of young women had BMI’s <20

HOW DOES A MOTHER’S

SMALL WAIST & LOW BMI

AFFECT HER CHILDREN?

OVULATORY INFERTILITY & BMI: 116,671 nurses, Rich-Edwards 2002

21

BMI<21:HARDER

TOGET

PREGNANT

In foraging/subsistence populations thinner women have fewer children

Hadza

Marlowe 04

Andes

Mueller 79

Papua New

Guinea

Brush 93

0 1 2 3

Low BirthWeight

Preterm

Hospital

<1919-2425+

Lower BMI, bad for infants

(infant)Murakami 2005

Low BMI & fetal or infant death

the lower the BMI,the moreinfant deaths

23

England

BMITennant, 2011

17

PUZZLEWHY DO MEN PREFER WOMEN

WITH LOWER FERTILITY& LESS HEALTHY INFANTS?

AND (OR) WHY DO MOST YOUNG

WOMEN HAVE SMALL WAISTS& LOW BMI’S?

WHAT HAPPENS TO A FIRST-TIME

AMERICAN MOTHER EVERY 86 SECONDS?

WH, 1932 (1847) Catherine

FTA, 1932 (1929)

Evolution of pelvis in humans

pelvis changed to allowupright walking and running

a

Smallest pelvic outlet dimension: interspinous diameter ~ 9 cm

Interspinous

Average biparietal diameter at term: 9.5 cm

humans have much less ofbrain growthbefore birth,but head isstill too big

chimpanzee

human

Almost half of babies from “normal”vaginal deliveries have bleeding in brain

46%

Rooks, 2008

LARGER HEAD LEADS TO BLOCKED LABORAND DEATH IN CHILDBIRTH

Spain, ~1100 AD

HOW COMMON WASDEATH IN CHILDBIRTH

BEFORE C-SECTIONS?

WHICHSEX

LIVES LONGER?

Average age at death,US 1999-2010

60 62 64 66 68 70 72 74 76

men

women

Percent surviving to age 65,US 1999-2010

60 65 70 75 80

men

women

Average adult age at death:30,000 BC to 1799 AD

26 28 30 32 34 36

~3000 skeletons examined by Larry Angel, 1984

men

women

Sweden, 1800-1899Hogberg, 1985

1 in 14 mothers died in childbirth

Sierra Leone 2.0%Afghanistan 1.9Malawi 1.8Angola 1.7Niger 1.6Tanzania 1.5Rwanda 1.4Mali 1.2

Maternal deaths in 2000, WHO

many mothers still die inchildbirth

Sierra Leone 1/50

0

5

10

15

20

25

1 2 3 4 5 6Birth

% C

-sec

tion

sFirst C-sections by birth

most risk ofblocked labor with first birth

US, 1990

Every 86 seconds a first-time American mother has a C-section

WHAT IS THE BENEFIT OF A

SMALLER WAIST& LOWER BMI

IN A FIRST-TIME MOTHER?

33.4

33.6

33.8

34.0

34.2

34.4

34.6

34.8

10-14 15-19 20-24 25-29 30-34 35-39

BMI before pregnancy

Hea

d s

ize

cmLower BMI, smaller newborn

head for 1st birth

05

10152025303540

12 14 16 18 20 22 24 26 28BMI before pregnancy

Per

cen

t C

-sec

tion

sLower BMI, fewer C-sections

for 1st birth

less blocked babies

High blood pressure duringpregnancy can also be bad

preeclampsia/eclampsia

0

1

2

3

4

1 2 3 4 5 6 7Pregnancy

Per

cen

t More high blood pressure with

first pregnancy

468

1012141618202224

14 16 18 20 22 24 26 28 30

Per

cent

pre

ecla

mps

iaBMI & high blood pressure

in 1st time mothers

lower BMI,less risk

WHAT ARE THE BENEFITS OF A

SMALLER WAIST& LOWER BMI

IN A FIRST-TIME MOTHER? (2)

1. LESS RISK OF MOTHER & CHILD

DYING IN CHILDBIRTH2. LESS HIGH

BLOOD PRESSURE

WHAT HAPPENS TOWOMEN’S WAIST FAT

(AND WEIGHT)AFTER

HAVING A CHILD?

252627282930313233

15 15 20 25 30 35 40 45 50Age Group

Wai

st, i

nche

sMinimum waist (inches) in women

with children, US 1988-94

NP

120

125

130

135

140

145

150

18 22 26 30 34 38 42 46Age

Wei

ght,

poun

dsAverage weight in American women

before obesity epidemic 1959-61

as add 25-30 pounds,more new fat in waist

20 21 22 23 24 25 26

Age 17-18

All Adults

BMI

Average BMI in European women

122 pounds

150 pounds

WHY IS IT BENEFICIALTO HAVE MORE

WAIST FAT AFTER HAVING A CHILD?

0 1 2 3

LBW

Preterm

Hospital

Adjusted Odds Ratio

<1919-2425+

Bigger waist, bigger babies

(infant)Murakami 2005

27.0

27.5

28.0

28.5

29.0

29.5

30.0

30.5

0 1 2 3 4 5 6Births

Pel

vic

wid

th, c

mPelvic width and births, NHANES III

birth canal expands with each birth, soless blocked labor

LESS HIGH BLOOD PRESSURE2nd CHILD WITH SAME FATHER

30

40

50

60

70

80

90

100

110

120

38 40 42 44 46 48 50 52 54 56 58 60 62

Waist/Height x 100

Insu

linBigger waist, more insulin resistance

more insulin resistance =more sugar for baby

= bigger baby

708090

100110120130140150160170

36 38 40 42 44 46 48 50 52 54 56 58 60 62

Waist/height x 100

Tri

glyc

erid

esBigger waist, more triglycerides

more fat inmother’s blood =bigger baby

0102030405060708090

100

20 21 22 23 24 25 26 27 28 29 30 31+

Cumulative BMI in women 15+

Per

cent

BMI in women 15+ in 190 countries

2/3rds are 25+“overweight”

WHERE WOMEN

DON’T ADD WAIST FAT,

CHILDREN SUFFER

(CONTROLLING FOR INCOME)

5

10

15

20

<22 22 23 24 25 26 27 28 29+

Female BMI

Low

Bir

th W

eigh

t %

Low birth weight & average BMI in women (income controlled)

0

10

20

30

40

50

<23 23 24 25 26 27 28 29+Female BMI

Dea

ths

per

100

0 b

irth

sNewborn death rate & average BMI

in women (income controlled)

25

50

75

100

125

<23 23 24 25 26 27 28 29+

Female BMI

Dea

ths

per

1000

bir

ths

Child death rate & average BMI in women (income controlled)

SO, WHY DOES A WOMAN

NEED WAIST FAT?

WAIST FATDETERMINESTHE SIZE OF

HER CHILDREN

WHAT ABOUT

FAT in the HIPS

& LEGS?

Jessica Rabbit

HIP/HEIGHT= 53%(36 in)

53% 53%

Playmateundergrad

53%

BMI <20

Hip/height

Men’s ranking of desirability ofwomen’s body areas

Rank Score 1-5Chest 1 4.13

Buttocks 2 4.09

Legs 3 4.04

Hips 4 3.98

Montoya, 2006

Almost all cultures value fat in women’s legs & hips

Brown & Konner, 1987

What % of weight is fat?

Ambelosi baboon

What % of weight is fat?

bear ready to hibernate

What % of weight is fat?

typicalundergrad

height: 64”weight: 132 lb

BMI: 22.2fat: 32%(42 lb)

WHY DO WOMENNEED

SO MUCH FAT?

2/3rds of fat is in hips & legs

(white = fat)

LOWER BODY FATIS LOCKED AWAY

UNTIL LATE INPREGNANCY

1800

2000

2200

2400

2600

0 1-6 7 8 9 nurseMonths of pregnancy

COST

30%of fetalgrowth

Mothers eat less in late pregnancy& while nursing (calories/day)

AS EAT LESS,LOWER BODY FATIS MOBILIZED IN

LATE PREGNANCY& WHILE NURSING

~1 ounce/day

WHAT IS INONE OUNCE OF LOWER-BODY

FAT?

0 50 100 150 200 250

human

baboon

beef cow

guinea pig

sheep

rabbit

rat/pig

Maternal energy cost of nursing: cals/kgPrentice 1988

300 calories/day

2% FAT

WHAT IMPORTANTORGAN IN

A NEW BABYGROWS THE MOST

& ADDS THE MOST FAT?

Brain triples in size in 1st year

300

400

500

600

700

800

900

Bra

in w

eig

ht,

g

Fat = 52% dry weight of brain

ProteinFat

Nerve cells are mostly membranes made of fat with embedded proteins

Nerve cell membranes would cover 5 football fields

DHA = 1/3rd of membrane fat

DHA

DOCOSAHEXAENOIC ACID

DHA (docosahexaenoic acid) omega-3

22 carbons6 double bonds

omega-3 fats must come from diet

DHA is active in every part of nerve cell

Calderon 07makes & grows dendrites

transmits signal

makessynapse work

grows axon

preserves

60

65

70

75

80

85

low medium highMother's dietary DHA

% h

igh

er I

QChildren of mothers with more DHA

while pregnant have higher verbal IQ’s

Hibbeln, 07

420

440

460

480

500

520

540

1 2 3 4+

Milk DHA index

Mat

h Sc

ore

More DHA in mother’s milk: higherPISA math score in 28 countries

WHERE DOES MILK DHA

COME FROM?

Where does milk DHA come from?

BODY FAT80%

CURRENTDIET

Fidler 2000

DHA mainly from stored fat80% of 120 mg

MILK DHA = 96 mg*

ONE OUNCEOF FAT =

96 mg* DHA

*120 mg DHA/day* European mothers

SO, WHY DO WOMENNEED SO MUCHLOWER-BODY

FAT?

LOWER-BODYFAT PROVIDES

ESSENTIAL FATSNEEDED BY BRAIN

WHY AREOUR

NEWBORNBABIESSO FAT?

TYPICAL NEWBORNHAS 2 POUNDS OF FAT

WITH1500 MILLIGRAMS OF

DHA

(1.6%)

HOW CAN WOMEN STORE MORE DHA WHEN

DHA % IN FAT IS LOWBECAUSE OF

LOW DHA FROM DIET?

Percent DHA in body fatImaichi 65, Leaf 95

0.0 0.2 0.4 0.6 0.8 1.0 1.2

US

Japan

0

5

10

15

20

25

30

1 2 3 4 5 6+Milk DHA index

Fem

ale

obes

ity

%DHA in mother’s milk &

female obesity in 43 countriesUSA?

Japan?paleolithic?

161820222426283032

30 32 34 36 38 40 42 44 46 48 50 52 54Waist/Height x 100

BM

IWaist/Height & BMI (Body Mass Index)

small waistrequires low BMI

correlation = 0.93

Playmates undergrads

Jessica?

1%2%

5

6

7

8

9

10 to 14 15 to 19 20 to 29

BMI

Low

bir

th w

eigh

t %

Lower BMI mothers have more low birth weight babies