The genetics of human fatness

Abstract Studies on the quantitative genetics of fatness are reviewed in the framework of the twin, adoption‐cohabitation, and familial aggregation methodologies. Low to moderate heritability of adult static fatness is evident. Somewhat less than one‐third of the variation appears ascribable to genetic causes. Genetic factors may play a greater role in childhood fatness, especially during adolescence. Comparison of studies is made difficult by many methodological shortcomings. These include a rarity of studies of adult first‐degree relatives “adulthood being the period in which fatness has the greatest health consequences”, different criteria of body fatness among studies, a lack of a full variety of genetic and adoptive relationships, inadequate sample sizes “especially in twin studies”, and unreported precision of fatness variables. Fatness change in the life cycle and the anatomical placement of fat are important modifiers of the health effects of obesity. Yet the genetics of these characteristics are little understood. Innovative statistical methods and study designs including path analysis, the family set method, and families of monozygous twins need wider application to the genetics of human fatness.