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 affe cted by heredity. The present study investigated the independence of t he heritability of overall daily intake from body size, meal intake fr om 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. wer e reanalyzed. A series of linear structural models were fit, using max imum likelihood estimation, to the identical and fraternal twin covari ance matrices for the body size, overall intake, and meal intake. Gend er and age were used as additional covariates. The results suggest tha t 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 varian ce 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 fro m 18% to 42% of the variance in average meal size is due to genetic in fluences independent of the overall daily intake, gender, and age of t he individual. On the other hand, the influence of heredity on the mac ronutrient composition of the meals was found to result, for the most part, secondarily from the genetic influence on overall meal size. The se results strongly suggest that there are separate genetic influences on body size, overall intake, and meal intake that have interacting i nfluences on one another. This indicates that inheritance has profound effects on body size and nutrient intake that are so salient and pote nt that they can be detected, independent of one another. in the spont aneous intake patterns of normal adult humans in their natural environ ments.