The changing relationship between bodyweight and longevity in high- and low-income countries.

Standard measures of bodyweight (overweight and obese, for example) fail to reflect differences across populations and technological progress over time. This paper builds on the pioneering work of Hans Waaler (1984) and Robert Fogel (1994) to empirically estimate how the relationship between body mass index (BMI) and longevity varies across high-, middle-, and low-income countries. Importantly, we show that these differences are so profound that the share of national populations above mortality-minimizing bodyweight is not clearly greater in countries with higher overweight and obesity rates (as traditionally defined)-and in fact, relative to current standards, a larger share of low-income countries' populations can be unhealthily heavy.