Weighing an important issue this summer

Sometimes I fancy myself a budding social scientist. I read a lot of economics, anthropology and sociology books for fun and each summer devote part of my leisure reading to more weighty works. Right now I'm particularly drawn to food science, so this year I'm boning up on the human diet.

The following is sort of a primer on popular scientific theories I plan to explore and share here in the coming months. Feel free to weigh in.

The Associated Press distilled a compendium of 100 scientific studies into 10 reasons we're weighing more these days. Here's a breakdown:

1. Inadequate sleep. (Average sleep amounts have fallen, and many studies tie sleep deprivation to weight gain.)

2. Endocrine disruptors, which are substances in some foods that may alter fats in the body.

3. Nice temperatures. (Air conditioning and heating limit calories burned from sweating and shivering.)

4. Fewer people smoking. (Less appetite supression.)

5. Medicines that cause weight gain.

6. Population changes. (More middle-agers and Hispanics, who have higher obesity rates.)

7. Older birth moms. (That correlates with heavier children).

8. Genetic influences during pregnancy.

9. Darwinian natural selection. (Fat people outsurvive skinny ones).

10. Assortative mating, or “like mating with like,” as Allison puts it. Translation: fat people procreating with others of the same body type, gradually skewing the population toward the heavy end.