Thursday, October 29, 2009

Childbirth and Evolution

From Half the Sky:

"One reason women die in childbirth has to do with anatomy, arising from two basic evolutionary trade-offs. The first is that once our ancient ancestors began to walk upright, too large a pelvis made upright walking and running inefficient and exhausting. A narrow pelvis permits fast running. That however makes childbirth exceedingly difficult. So the evolutionary adaptation is that women generally have medium-sized pelvises that permit moderately swift locomotion and allow them to survive childbirth - most of the time.

The other trade-off is head size. Beginning with our Cro-Magnon ancestors, human skull size expanded to accommodate more complex brains. Larger brains offer an evolutionary advantage once a child is born, but they increase the chance that a large-headed fetus will never emerge alive from the mother."


Thursday, October 8, 2009

Wednesday, October 7, 2009

Improving Self Reported BMI

Many epidemiological studies measure adiposity (obesity) through the surrogate BMI via self reported measures of height and weight. As I have mentioned before, there are many problems with this. But how can we improve on this while maintaining our level of accuracy and not using a direct measure requiring a more intensive doctor visit?

Two ideas to use along with BMI:
1. Waist size - pant size for men, dress size for women
2. Bench press - probably more reasonable for men. Could use max (weight you can bench press once), or weight you can bench press ten times.