ABSTRACT
Family, twin, and adoption studies have provided evidence for cultural and biological inheritance in human behavior and health (1). Because currently known genes account for only a fraction of the estimated genetic variance of obesityrelated traits, more knowledge of the dynamics of gene action and of specific environmental conditions is needed. Longitudinal twin and twin-family studies with multiple measurements can permit a more detailed assessment of the developmental aspects of obesity-related factors and how the relative roles of genes and environment unfold over time.
