Another What You Didn't Know segment of A Moment of Science.   Don: Time once again for What You Didn't Know. This is the segment where I give Yael a science fact that everybody thinks they know already, then wow her with the follow-up. Ready?

Yael: Ready.

D: Obesity is bad for men.

Y: Big surprise, Marcus Welby.

D: ...because it lowers their mental ability.

Y: Obesity lowers mental ability? I never heard that.

D: It's true. You've already heard that fat make things hard on the heart, for example, as well as making diabetes and even certain cancers more likely. A study published in the International Journal of Obesity, however, shows that fat doesn't just slow down your jump-shot--it can even slow down your brain. Over five hundred men and eight hundred women were observed for eighteen years in this long-term study, all of whom took tests at different times to gauge how quick their thinking was. In the men, obesity was positively correlated with a decline in thinking ability. It's already known that the way men store body fat--the apple shape with a wide middle--causes more health problems than the pear shape more common to women.

Y: But what could your obesity have to do with how well you think?

D: That part isn't known. It may be that obesity equals problems in blood pressure, which is important for brain function. It may be that subtle forms of heart disease are present. Other scientists think the link may be psychological--overweight people tend to get depressed, and depression slows down thinking. But whatever the link is, if you're a guy, it's not just your mid-section that needs taking care of...it's your brain.