Obesity

Population studies that try to link average life duration and average obesity are confouded by numerous factors, especially medical progress. However, virtually every study that I have seen that correlates body weight with disease prevalence finds a U shaped curve with minimum incidence rates at a BMI of about 22/23. Lower than this you are probably starving yourself or sick; higher and you are hurting yourself. Besides the usual cardiovasular and diabetes these results are common across many cancers, a range of other diseases and aging in general. These results are backed up by physiological evidence of cumulative negative impacts of bloated fat cells on the body.

There are some considerations that that weaken these results, especially the correlation between BMI and sedentry lifestyle. On the other hand, while BMI is easy to measure, it is an imperfect measure of obesity. Body shapes vary and research is indicating that it’s fat around the gut – aka “male fat” that is the problem more than distributed fat. (Or female fat on the breasts and hip which requires physiological effort to maintain so is a sign of youthful good health.) If a better fat measurements were used the impact of obesity on disease would probably increase.

None of this stuff is completely rock solid but the indications are pretty plain. The fact that you might now have an increased life expectancy despite being overweight doesn’t mean that much if the extra life is spent in a poor state of health, unable to do much, and kept alive by drugs. I aim to get as close you can reasonably manage to a BMI around 23 while maintaining activity and equanimity. People should take general body shape and fat distribution into account as well as the simple number.

(crossposted comment at johnquiggin.com)