Title's a bit misleading. The study actually found that mothers with a <i>low</i> waste-hip ratio had smarter kids. That translates to big hips (and narrow waist), not the image of rolls of fat and a gigantic gut that normally come to mind when you say "fat moms".<p>Also, I'm curious if they actually measured polyunsaturated fat levels and correlated them. I've heard other studies that suggested big hips lead to healthier, smarter children because they lead to easier childbirths and inflict less trauma on the fetus during delivery. They could control for this by testing a group of kids delivered by caesarean.
Correlation != Causation<p>It drives me crazy when I hear stories about "Children who [play an instrument / listen to classical music / have a pet] are smarter than average".<p>While that itself may be true, the implication that one causes the other most likely isn't. It's far more likely that a kid is smart AND plays an instrument or listens to classical music because their <i>parents</i> foster that sort of environment.<p>If your kid is dumb, making him listen to classical music isn't going help. There was a great Penn and Teller "Bullshit!" episode about this: <a href="http://www.sho.com/site/ptbs/prevepisodes.do?episodeid=s1/bb" rel="nofollow">http://www.sho.com/site/ptbs/prevepisodes.do?episodeid=s1/bb</a>
Humans are born as physiological fetuses to allow further growth of the skull. There is a natural limit to how early a child can be born, and therefore a natural limit on the size of heads. Human females have adapted wide hips to account mainly for the size of the brain, but there is a practical limit to that as well. The cesarean section will perhaps allow further increase in human intelligence.<p>If the hip-fat theory is correct, then other bodily fats should have a similar effect. I am guessing I could find data that suggests large-assed females actually have children with lower IQs, though I doubt I could get a grant for that.
Studies like this have a simple formula:<p>Find a correlation.<p>Make up a cause.<p>Pretend the correlation implies that cause, when in fact they have found absolutely zero evidence whatsoever of their conclusion.<p>Get published.