INDEPENDENCE OF GENETIC INFLUENCES ON BODY-SIZE, DAILY INTAKE, AND MEAL PATTERNS OF HUMANS

Body size and daily and meal trient intakes have been shown to be affected by heredity. The present study investigated the independence of the heritability of overall daily intake from body size, meal intake from overall daily intakes, and meal macronutrient intake from meal size. Previously collected 7-day food intake diary data obtained from 109 identical and 86 fraternal adult twin pairs, who lived separately. were reanalyzed. A series of linear structural models were fit, using maximum likelihood estimation, to the identical and fraternal twin covariance matrices for the body size, overall intake, and meal intake. Gender and age were used as additional covariates. The results suggest that 96% of the variance in height and 85% of the variance in weight are due to heredity. They also indicate that from 25% to 50% of the variance in daily food intake and from 22% to 48% of the variance in average meal size is due to genetic influences independent of the body size, gender, and age of the individual. Furthermore, they indicate that from 18% to 42% of the variance in average meal size is due to genetic influences independent of the overall daily intake, gender, and age of the individual. On the other hand, the influence of heredity on the macronutrient composition of the meals was found to result, for the most part, secondarily from the genetic influence on overall meal size. These results strongly suggest that there are separate genetic influences on body size, overall intake, and meal intake that have interacting influences on one another. This indicates that inheritance has profound effects on body size and nutrient intake that are so salient and potent that they can be detected, independent of one another. in the spontaneous intake patterns of normal adult humans in their natural environments.