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AHS13 Will Lassek MD -- Why Women Need Fat: Three Evolutionary Puzzles
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AHS13 Will Lassek MD -- Why Women Need Fat: Three Evolutionary Puzzles

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Dr. Lassek's talk may be viewed here: …

Dr. Lassek's talk may be viewed here:
http://www.youtube.com/watch?v=gJhT_ANNy4E

Abstract: One puzzle is why human males have such a strong preference for women with hourglass figures and low weights that can compromise fertility. The second is why slender young women typically have about one third of their weight in body fat, more than bears starting to hibernate, and why human infants are also very fat. Finally, why do women typically gain another twenty pounds or more during their reproductive years? The answer may lie in the roles that fat plays in providing essential fatty acids needed for the growth of a very large brain and in regulating overall fetal growth.


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    • 1. WHY DO WOMEN NEED FAT? Will Lassek
    • 2. Look here first
    • 3. Who is the most attractive imaginary woman? eg. animated films, video games, comics, graphic novels
    • 4. Jessica Rabbit “most attractive imaginary woman” 650 undergrads of Steve Gaulin “sexiest cartoon character” Cadbury contest
    • 5. What is her most unusual attribute?
    • 6. Jessica Rabbit Waist/Hip Ratio: 38% Waist/Height Ratio: 15% (10 inches)
    • 7. 38% 68% 74% WAIST/HIP Playmate undergrad
    • 8. 15% 10 in 36% 24 in 44% 28 in WAIST/HEIGHT Playmate undergrad
    • 9. WHERE DO MEN LOOK FIRST & LONGEST?
    • 10. Cornellisen, et al. 2009 Look here first eye tracking: WAIST is where men look first and most when judging attractiveness
    • 11. Why should we care what men find attractive? Look here first
    • 12. Men should admire qualities that help women have children that survive
    • 13. HOW IS WOMEN’S WAIST FAT CONNECTED TO HAVING CHILDREN?
    • 14. BMI Waist & BMI (Body Mass Index) 32 small waist 30 28 requires low BMI 26 correlation = 0.93 24 22 Playmates 20 undergrads 18 16 14 20 22 24 26 28 30 32 34 36 Jessica’s BMI? Waist, inches
    • 15. Jessica Rabbit waist/height 15% predicted BMI: 10 (from waist, hip, height)
    • 16. Average weight of young US women by BMI 150 Pounds 140 130 BMI <20 <120 pounds 120 110 100 90 16 17 18 19 20 21 BMI 22 23 24 25
    • 17. Men prefer women with low BMI’s Martin Tovee, et al. 1999 attractiveness scores
    • 18. Cumulative BMI % age 18-20, 1971-75 (before the obesity epidemic) 50 Percent 40 30 half of young women had BMI’s <20 20 10 0 14 15 16 17 BMI 18 19
    • 19. HOW DOES A MOTHER’S SMALL WAIST & LOW BMI AFFECT HER CHILDREN?
    • 20. OVULATORY INFERTILITY & BMI: 116,671 nurses, Rich-Edwards 2002 21 BMI<21: HARDER TO GET PREGNANT
    • 21. In foraging/subsistence populations thinner women have fewer children Papua New Guinea Andes Brush 93 Mueller 79 Hadza Marlowe 04
    • 22. Lower BMI, bad for infants 0 Low Birth Weight Preterm 1 2 <19 19-24 25+ Hospital (infant) Murakami 2005 3
    • 23. Low BMI & fetal or infant death England BMI 17 23 the lower the BMI, the more infant deaths Tennant, 2011
    • 24. PUZZLE WHY DO MEN PREFER WOMEN WITH LOWER FERTILITY & LESS HEALTHY INFANTS? AND (OR) WHY DO MOST YOUNG WOMEN HAVE SMALL WAISTS & LOW BMI’S?
    • 25. WHAT HAPPENS TO A FIRST-TIME AMERICAN MOTHER EVERY 86 SECONDS?
    • 26. WH, 1932 (1847) Catherine
    • 27. FTA, 1932 (1929)
    • 28. Evolution of pelvis in humans pelvis changed to allow upright walking and running
    • 29. Smallest pelvic outlet dimension: interspinous diameter ~ 9 cm a Interspinous
    • 30. Average biparietal diameter at term: 9.5 cm
    • 31. human chimpanzee humans have much less of brain growth before birth, but head is still too big
    • 32. Almost half of babies from “normal” vaginal deliveries have bleeding in brain 46% Rooks, 2008
    • 33. LARGER HEAD LEADS TO BLOCKED LABOR AND DEATH IN CHILDBIRTH Spain, ~1100 AD
    • 34. HOW COMMON WAS DEATH IN CHILDBIRTH BEFORE C-SECTIONS?
    • 35. WHICH SEX LIVES LONGER?
    • 36. Average age at death, US 1999-2010 60 62 64 66 68 70 72 74 76 men women
    • 37. 60 Percent surviving to age 65, US 1999-2010 65 70 men women 75 80
    • 38. 26 Average adult age at death: 30,000 BC to 1799 AD 28 30 32 34 36 men women ~3000 skeletons examined by Larry Angel, 1984
    • 39. Sweden, 1800-1899 Hogberg, 1985 1 in 14 mothers died in childbirth
    • 40. Maternal deaths in 2000, WHO many mothers Sierra Leone still die in Afghanistan childbirth Malawi Sierra Leone 1/50 Angola Niger Tanzania Rwanda Mali 2.0% 1.9 1.8 1.7 1.6 1.5 1.4 1.2
    • 41. First C-sections by birth US, 1990 25 most risk of blocked labor with first birth % C-sections 20 15 10 5 0 1 2 3 Birth 4 5 6
    • 42. Every 86 seconds a first-time American mother has a C-section
    • 43. WHAT IS THE BENEFIT OF A SMALLER WAIST & LOWER BMI IN A FIRST-TIME MOTHER?
    • 44. Head size cm Lower BMI, smaller newborn 34.8 st head for 1 birth 34.6 34.4 34.2 34.0 33.8 33.6 33.4 10-14 15-19 20-24 25-29 30-34 BMI before pregnancy 35-39
    • 45. Percent C-sections Lower BMI, fewer C-sections st 40 for 1 birth 35 30 25 20 15 10 5 0 less blocked babies 12 14 16 18 20 22 24 26 28 BMI before pregnancy
    • 46. High blood pressure during pregnancy can also be bad preeclampsia/eclampsia
    • 47. More high blood pressure with first pregnancy Percent 4 3 2 1 0 1 2 3 4 5 Pregnancy 6 7
    • 48. Percent preeclampsia BMI & high blood pressure st in 1 time mothers 24 22 20 18 16 14 12 10 8 6 4 lower BMI, less risk 14 16 18 20 22 24 26 28 30
    • 49. WHAT ARE THE BENEFITS OF A SMALLER WAIST & LOWER BMI IN A FIRST-TIME MOTHER? (2)
    • 50. 1. LESS RISK OF MOTHER & CHILD DYING IN CHILDBIRTH 2. LESS HIGH BLOOD PRESSURE
    • 51. WHAT HAPPENS TO WOMEN’S WAIST FAT (AND WEIGHT) AFTER HAVING A CHILD?
    • 52. Waist, inches Minimum waist (inches) in women 33 with children, US 1988-94 32 31 30 29 28 27 26 25 NP 15 15 20 25 30 35 40 45 50 Age Group
    • 53. Average weight in American women 150before Weight, pounds 145 obesity epidemic 1959-61 140 135 130 125 120 as add 25-30 pounds, more new fat in waist 18 22 26 30 34 38 42 46 Age
    • 54. Average BMI in European women 20 Age 17-18 All Adults 21 BMI 22 23 24 122 pounds 150 pounds 25 26
    • 55. WHY IS IT BENEFICIAL TO HAVE MORE WAIST FAT AFTER HAVING A CHILD?
    • 56. Bigger waist, bigger babies 0 Adjusted Odds Ratio 1 2 3 LBW Preterm <19 19-24 25+ Hospital (infant) Murakami 2005
    • 57. Pelvic width, cm Pelvic width and births, NHANES III 30.5 30.0 29.5 29.0 28.5 28.0 27.5 27.0 birth canal expands with each birth, so less blocked labor 0 1 2 3 4 Births 5 6
    • 58. LESS HIGH BLOOD PRESSURE 2nd CHILD WITH SAME FATHER
    • 59. Insulin Bigger waist, more insulin resistance 120 110 100 90 80 70 60 50 40 30 more insulin resistance = more sugar for baby = bigger baby 38 40 42 44 46 48 50 52 54 56 58 60 62 Waist/Height x 100
    • 60. Triglycerides Bigger waist, more triglycerides 170 160 more fat in 150 mother’s blood = 140 130 bigger baby 120 110 100 90 80 70 36 38 40 42 44 46 48 50 52 54 56 58 60 62 Waist/height x 100
    • 61. BMI in women 15+ in 190 countries 2/3rds are 25+ “overweight” Percent 100 90 80 70 60 50 40 30 20 10 0 20 21 22 23 24 25 26 27 28 29 30 31+ Cumulative BMI in women 15+
    • 62. WHERE WOMEN DON’T ADD WAIST FAT, CHILDREN SUFFER (CONTROLLING FOR INCOME)
    • 63. Low Birth Weight % Low birth weight & average BMI 20 in women (income controlled) 15 10 5 <22 22 23 24 25 26 Female BMI 27 28 29+
    • 64. Deaths per 1000 births Newborn death rate & average BMI in women (income controlled) 50 40 30 20 10 0 <23 23 24 25 26 27 28 29+ Female BMI
    • 65. Child death rate & average BMI in women (income controlled) Deaths per 1000 births 125 100 75 50 25 <23 23 24 25 26 27 Female BMI 28 29+
    • 66. SO, WHY DOES A WOMAN NEED WAIST FAT?
    • 67. WAIST FAT DETERMINES THE SIZE OF HER CHILDREN
    • 68. WHAT ABOUT FAT in the HIPS & LEGS?
    • 69. Jessica Rabbit HIP/HEIGHT = 53% (36 in)
    • 70. 53% 53% 53% Hip/height BMI <20 Playmate undergrad
    • 71. Men’s ranking of desirability of women’s body areas Rank Score 1-5 Chest 1 4.13 Buttocks 2 4.09 Legs 3 4.04 Hips 4 3.98 Montoya, 2006
    • 72. Almost all cultures value fat in women’s legs & hips Brown & Konner, 1987
    • 73. What % of weight is fat? Ambelosi baboon
    • 74. What % of weight is fat? bear ready to hibernate
    • 75. What % of weight is fat? typical undergrad
    • 76. height: 64” weight: 132 lb BMI: 22.2 fat: 32% (42 lb)
    • 77. WHY DO WOMEN NEED SO MUCH FAT?
    • 78. 2/3rds of fat is in hips & legs (white = fat)
    • 79. LOWER BODY FAT IS LOCKED AWAY UNTIL LATE IN PREGNANCY
    • 80. Mothers eat less in late pregnancy 2600& while nursing (calories/day) 30% of fetal growth 2400 2200 2000 1800 0 1-6 7 8 9 nurse Months of pregnancy COST
    • 81. AS EAT LESS, LOWER BODY FAT IS MOBILIZED IN LATE PREGNANCY & WHILE NURSING ~1 ounce/day
    • 82. WHAT IS IN ONE OUNCE OF LOWER-BODY FAT?
    • 83. Maternal energy cost of nursing: cals/kg Prentice 1988 rat/pig rabbit sheep guinea pig beef cow 2% FAT baboon human 300 calories/day 0 50 100 150 200 250
    • 84. WHAT IMPORTANT ORGAN IN A NEW BABY GROWS THE MOST & ADDS THE MOST FAT?
    • 85. Brain triples in size in 1st year Brain weight, g 900 800 700 600 500 400 300
    • 86. Fat = 52% dry weight of brain Fat Protein
    • 87. Nerve cells are mostly membranes made of fat with embedded proteins
    • 88. Nerve cell membranes would cover 5 football fields
    • 89. DHA = 1/3 of membrane fat rd DOCOSAHEXAENOIC ACID DHA
    • 90. DHA (docosahexaenoic acid) omega-3 22 carbons 6 double bonds omega-3 fats must come from diet
    • 91. DHA is active in every part of nerve cell makes synapse work grows axon transmits signal makes & grows dendrites preserves Calderon 07
    • 92. Children of mothers with more DHA while pregnant have higher verbal IQ’s % higher IQ 85 80 75 70 65 60 low medium high Mother's dietary DHA Hibbeln, 07
    • 93. More DHA in mother’s milk: higher PISA math score in 28 countries 540 Math Score 520 500 480 460 440 420 1 2 3 Milk DHA index 4+
    • 94. WHERE DOES MILK DHA COME FROM?
    • 95. Where does milk DHA come from? CURRENT DIET BODY FAT 80% Fidler 2000
    • 96. DHA mainly from stored fat 80% of 120 mg MILK DHA = 96 mg* ONE OUNCE OF FAT = 96 mg* DHA *120 mg DHA/day * European mothers
    • 97. SO, WHY DO WOMEN NEED SO MUCH LOWER-BODY FAT?
    • 98. LOWER-BODY FAT PROVIDES ESSENTIAL FATS NEEDED BY BRAIN
    • 99. WHY ARE OUR NEWBORN BABIES SO FAT?
    • 100. TYPICAL NEWBORN HAS 2 POUNDS OF FAT WITH 1500 MILLIGRAMS OF DHA (1.6%)
    • 101. HOW CAN WOMEN STORE MORE DHA WHEN DHA % IN FAT IS LOW BECAUSE OF LOW DHA FROM DIET?
    • 102. Percent DHA in body fat Imaichi 65, Leaf 95 Japan US 0.0 0.2 0.4 0.6 0.8 1.0 1.2
    • 103. Female obesity % DHA in mother’s milk & female obesity in 43 countries 30 25 USA? Japan? paleolithic? 20 15 10 5 0 1 2 3 4 Milk DHA index 5 6+
    • 104. BMI Waist/Height & BMI (Body Mass Index) 32 small waist 30 28 requires low BMI 26 correlation = 0.93 24 22 undergrads 20 Playmates 18 16 30 32 34 36 38 40 42 44 46 48 50 52 54 Jessica? Waist/Height x 100
    • 105. 2% 1%
    • 106. Low birth weight % Lower BMI mothers have more 9 low birth weight babies 8 7 6 5 10 to 14 15 to 19 BMI 20 to 29