Another reason why?

men like curves

 By Gary Cleland

The study, to be published, shows that men who admire women with hourglass figures do so because they are more intelligent and therefore produce more intelligent children than waif-like women or those of "apple-shaped" proportions.

The scientists, from the University of California at Santa Barbara and the University of Pittsburgh, concluded that women with lower waist-to-hip ratios (WHR) produced children with better intellectual abilities.

They found that a woman's hips and thighs contained omega-3 fatty acids, which help nurture both mother and baby's brains during pregnancy.

Fat around the waist, however, contains higher levels of omega-6 fatty acids, which does not help brain growth.

"Shapely hips and thighs hold essential nutrients that nurse brains and could produce smart kids, too," said one researcher, Steven Gaulin, of the University of California at Santa Barbara. His colleague, William Lassek, from the University of Pittsburgh, said: "Men respond because it's reproductively important."

Scientific studies have consistently demonstrated that men through the ages have found women with hourglass figures more attractive.
A study published this year found that as far back as the ancient Egyptians men have sought out curvaceous women.

However, the reason for the attraction has never been conclusively proven. Many scientists believed that a shapely figure suggested to a man that a woman would be good at be baring children and have a longer life expectancy.

The researchers tested 16,000 women and girls and found that women with a greater difference between their waist and hip measurements scored significantly higher in the tests, as did their children.

The research suggests that children born to teenagers do worse in cognitive tests because their mothers did not have enough of the omega-3 acids stored in their hips.

© Copyright of Telegraph Media Group Limited 2007

RE-vised 2008 

 Relationship between female body shape & brain function
Steven Gaulin, Ph.D.
Professor of Anthropology
UC Santa Barbara
gaulin@anth.ucsb.edu 

Our research questions: My collaborator, Will Lassek, and I began by trying to understand three things:

Q.   1. Why are women’s bodies much fattier than mens ? Among normal, healthy individuals, mens bodies are about 10-12% fat and women’s are 25-30% fat, as a percentage of body weight.

Q.   2. Why do men and women distribute their body fat differently? Men distribute their fat abdominal whereas women deposit theirs below the waist (in hips and thighs) and to a more variable degree, above the waist in their breasts.

The result of this sex difference in fat distribution is that women have lower waist/hip ratios than men.

(The waist/hip ratio is simply the circumference of the waist measured at the narrowest part divided by the circumference of the hips measured at the widest part.) 

Q.   3. Why do men pay attention to female fat distribution in evaluating female attractiveness?

Most people will not doubt this claim but, just in case, there is a substantial scientific literature documenting that men find women with low waist/hip ratios more attractive. 

What we did and Learned ? 

We brought together what is presently known about fat metabolism to develop some hypotheses, and we tested these hypotheses on a large federally-collected database to explore these questions.

Here’s what we found 

A.   1. Women’s extra fat is not primarily to support the caloric demands of pregnancy and lactation. If that were so then all mammals would show a sex difference in body fat. In general, mammals (including our close relatives like chimpanzees) show no sex differences in body fat. The calorie hypothesis must be wrong.

A.   2. Not counting water (all our organs are mostly water) brains are over 50% fat. And brain fat is special fat. For example, saturated fat won’t do, nor will most other kinds. Only a few kinds of long-chain, polyunsaturated fatty acids (LCPUFA’s), such as EPA and DHA, are important brain constituents. Mostly we synthesize these LCPUFA’s from dietary precursors but some foods (e.g., seafood) contain significant amounts of LCPUFA.

A.   3. LCPUFA’s tend to be stored in the hips and thighs (whereas saturated fat is stored abdominal).

A.   4. Most fat depots (areas of the body where fat is stored) are like checking accounts with frequent deposits and withdrawals. In contrast, the hip and thigh depots are more like certificates of deposit; withdrawals can only be made at particular times. Hip and thigh fat is primarily metabolized during the third trimester of pregnancy and during lactation. This is when the infant brain is being built. 

A.   5. Thus, women carry more fat than men, especially in the hips and thighs, not for the calories but for the materials (LCPUFA’s) they need to build their children’s brains. Men don’t need so much of this fat because they don’t build infant brains.

A.   6. But why is tummy fat bad? Couldn’t a woman with big hips and thighs and a big tummy provide just as much LCPUFA and a woman with big hips and thighs and a small tummy? No. Tummy fat inhibits the synthesis (from dietary precursors) of the brain-critical LCPUFA’s. (It does this by inhibiting the production of delta-5 desaturase, an enzyme necessary for the assembly of LCPUFA’s.)

A.   7. Women with small tummies and big hips and thighs have more of what it takes to build brains and thus tend to be smarter themselves and have smarter children. This is our principal finding, based on actual measurements of fat distribution and cognitive performance from the federally collected data base (NHANES III). We controlled statistically for things like parental education and income, and with these statistical adjustments, waist/hip ratio was still a significant predictor of cognitive performance.

A.   8. As a proportion of total body fat, women loose hip and thigh fat with every pregnancy. This is not a simple result of age; it is related to the number of children she has had, controlling for age. Women “spend” hip and thigh fat, and accumulate tummy fat, with each pregnancy. This could explain the well-known correlation between birth order and IQ. 

A.   9. It’s well known that teenage mothers tend to have offspring with lower cognitive ability. Why? There could be many reasons but we thought it could be because they must divide their LCPUFA’s between their own brain, which is still developing, and their infant’s. In support of this view, our study showed that teenage mothers with low waist /hip ratios (those with lots of LCPUFA) did NOT have offspring with depressed cognitive ability. Of course we’re not advocating teen pregnancy but this result suggests that it’s LCPUFA shortage, not teen status perse that harms the infant’s cognitive development.

A.   10. Humans have very large brains (for example 3.5 times larger than chimpanzee brains) and thus face unusually high LCPUFA demands. This explains the male preference for low waist/hip ratios. Women with low waist/hip ratios are providing physical evidence that they can build the definitively human adaptation: a big, powerful brain.

A.   11. Changes in the American food supply (an increasing reliance on corn) have reduced the amount of LCPUFA and LCPUFA precursors in our diet. These dietary shifts are changing women’s body shapes, but do they also explain why the USA is last among developed nations in math and science? Food for thought...

The preceding summary is based on: Lassek, W.D. & Gaulin, S.J.C. (2008). “Waist-hip ratio and cognitive ability: is glute of emoral fat a privileged store of neuro developmental resources?” This article is in press and will appear in the January 2008 issue of Evolution and Human Behavior. It has already been published on-line on the journal’s web site.
Permission of artical use by Steven Gaulin, Ph.D.
Professor of Anthropology
UC Santa Barbara
All credits given to the author(s).