Do economic constraints on food choice make people fat? A critical review of two hypotheses for the poverty-obesity paradox.

In low income countries worldwide, rising standards of living have spurred an unprecedented rise in obesity. However, in numerous wealthy countries the trend frequently reverses with poorer and less educated women more likely to be overweight than their wealthier compatriots. One prominent explanation for this reverse gradient is that economic deprivation leads to food choices which paradoxically increase energy intake. If true, this would challenge current evolutionary accounts for the modern obesity epidemic and have serious implications for how policy makers tackle increasing obesity in the US and worldwide. In this article, we critically review the hypothesis that deprivation leads people to choose cheaper foods which in turn foster overconsumption of energy. Though the hypothesis is consistent with numerous cross-sectional studies, available longitudinal studies from high-, middle-, and low-income countries show the reverse-that when populations experience resource declines, they experience either declines in BMI or decelerations in BMI growth. Most notably, the recent recession in the US coincides with a clear deceleration in women's obesity across income groups. We conclude by briefly reviewing other plausible explanations for the reverse gradient among women in developing countries. Finally, we discuss how theoretical perspectives and comparative, historical approaches from human biology are useful tools for examining the current wealth of hypotheses about obesity in population health.