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 technological progress over time - and in particular, recent progress disproportionately promoting longevity at higher bodyweights (and differences in access to it). This paper builds on the pioneering work of Hans Waaler (Waaler, 1984) and Robert Fogel (Fogel, 1994) to empirically estimate how technological progress, and differential access to it, have fundamentally transformed the relationship between body mass index (BMI) and longevity in high-, middle-, and low-income countries. Importantly, we show that the combined effect of technological progress and access to it across countries is 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.