## Sunday, January 11, 2009

Skinny guys have few children: The last post on sex and weight got me wondering about fertility.  Here are the mean number of children that people 40 and over have had:

Mean number of children

Men, N = 611
Below average weight 1.08
Average 2.11
Above average 2.23
Considerabily above above 1.83

Women, N = 717
Below average weight 2.14
Average 2.36
Above average 2.14
Considerabily above above 2.12

The item that jumps out at you is skinny men: they have half the children that others have. What's up with that?

1. Anonymous7:51 PM

If weight, rather than BMI or something similiar, is the sole criterium it isn't all that strange.

Then the below average weight guys include a lot of simply small guys, and that's a group that's not at all popular with women.

/John F

2. Anonymous2:42 AM

isn't there a correlation between class and weight? also single and gay men have more incentive to stay thin.

3. Anonymous6:30 AM

It could be just a quirk resulting from a very low n= field. The survey is limited to people age 40 and over, and there aren't a whole lot of middle-aged men who weigh less than average (in terms of average for all men).

Peter

4. You do not know how fat they were when they conceived the children. Doesn't parenting make you fatter?

5. This comment has been removed by the author.

6. iron: The sample of skinny men is 26. At the 95% confidence level, the skinny guys have significantly fewer kids than everyone except the considerably above average men and women.

7. Considerably Above Above6:56 PM

I'm going to go with the hypothesis that it's not BMI we're measuring here, it's actual physical size.

8. I'm thinking John F and others have nailed this one. Height and muscles both add weight, and those are two ingredients in male attractiveness.

What I would really like to see is a correlation between the simple-yet-effective ratio of height-to-waistline which is said to be the best (simple) indicator of fatness (beating out BMI, which seems to treat muscley guys as being fat). My guess is that your truly SKINNY guys will be reproducing less - anorexia nervosa being no healthier in men than in women - but that lanky / trim gents will do okay.

My guess (further out on the limb) is that the lanky / trim gents may do BETTER than the big-waistline men who are equidistant from the ratio's mean, but that heavier, moderate waistline men will do best of all. NOT because women only want to reproduce with body builders, but because you can't be both heavy and have a moderate waistline if you have a slew of health problems.

So there you have my hypothesis. Now all I need is a grant and a team of graduate students....

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11. Anonymous3:51 PM