Current trends in adult obesity threaten global health. Although the implications of changes in diets, lifestyles, and food environments have been examined, the specific role of excess calorie availability (ECA)—understood as calorie availability in excess of human requirements for a healthy life—and the cohort mechanisms that underlie trends in adult body mass index (BMI) are poorly understood. We examine these relationships for 156 countries over the past century using an age-, sex-, and cohort-specific approach. We measure the association between increases in food energy supply and changes in BMI across countries and time. We find positive and significant associations between ECA and adult BMI for both males and females, and between ECA during early childhood and BMI at adulthood for males. We also find a strengthening of these correlations over successive generations. These cohort mechanisms are boosted by age effects, leading individuals in each successive cohort to reach unhealthy BMI levels at younger ages. Individuals in more recent cohorts are overweight or obese earlier and for larger proportions of their lifespan than those in earlier cohorts. Even after controlling for development dynamics, the pattern is consistent across countries and appears to be driven, in part, by availability of calories in excess of underlying requirements. Our findings provide novel insights into the role of ECA, and potential unintended health consequences of agricultural and trade policies directed at increasing calorie supplies.
BMI; Cohort effects; Calorie availability; Global trends; Human nutrition