Seven models of population obesity.

Obesity is new in human evolutionary history, having become possible at the population level with increased food security. As with any phenotype, obesity is at base an outcome of gene-environment interactions. However, different disciplines working in obesity research have identified different facets of the problem and developed different models of population obesity. These include those of thrifty genotypes, obesogenic behavior, obesogenic environments, nutrition transition, obesogenic culture, and biocultural interactions of genetics, environment, behavior, and culture. Although there is an overlap between various of these models, there remains a lack of consensus concerning obesity causation at the population level. This is a major problem in study of, and intervention in, obesity among populations.