A TWIN STUDY OF THE EFFECTS OF ENERGY DENSITY AND PALATABILITY ON ENERGY INTAKE OF INDIVIDUAL FOODS

Authors: MCCRORY, MEGAN - TUFTS-HNRCA; SALTZMAN, EDWARD - TUFTS-HNRCA; ROLLS, BARBARA - PENNSYLVANIA STATE UNIV; ROBERTS, SUSAN - TUFTS-HNRCA

Submitted to: Physiology & Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/21/2004
Publication Date: 3/30/2006
Citation: Mccrory, M.A., Saltzman, E., Rolls, B.J., Roberts, S.B. 2006. A twin study of the effects of energy density and palatability on energy intake of individual foods. Physiology and Behavior. 87(3):451-9.

Interpretive Summary: In this study we examined monozygotic twin pairs to test the hypothesis that there are familial influences on the extent to which energy density and taste pleasantness (an index of palatability) separately influence energy intake and changes in energy intake over time. We also determined the relative influences of energy density and taste pleasantness on energy intake from 22 different foods over two 9-d test periods. Some twin pairs were particularly susceptible to the effects of energy density, and increased their consumption of foods high in energy density over time. This finding suggests that there are familial influences on the susceptibility to overeating foods high in energy density, and further studies in this area are needed to determine the extent to which these familial influences are genetic or learned. In addition, energy density was shown to have both a direct effect on energy intake and an indirect effect operating through its association with taste pleasantness. More studies using a greater number of foods and subjects are needed to confirm these findings.

Technical Abstract: The relative effects of energy density and palatability on energy intake, and whether there are familial influences on these effects, are not known. We investigated this issue in 7 pairs of healthy, male monozygotic twins (mean±SD age 26.3±8.6 y, BMI 23.7±3.2 kg/m2) in a clinical study involving covert ad libitum feeding of high-fat (HF, ~40%) and low-fat (LF, ~20%) diets in two 9-d phases. Diets were matched for average energy density, protein, fiber, and initial reported taste pleasantness, but these factors varied among the individual foods. Relationships between energy density, palatability, and energy intake were explored using regression and path analyses. Food energy density was positively associated with average taste pleasantness (r=0.46, P=0.03) independent of fat content, while energy intake from individual foods was positively associated with both energy density (r=0.56, P=0.007) and taste pleasantness (r=0.73, P<0.0001). In path analysis, both energy density and taste pleasantness directly influenced energy intake, and energy density also indirectly influenced energy intake by influencing taste pleasantness. In addition, there were significant within-twin pair similarities for the energy density-taste pleasantness and energy density-energy intake relationships (P<0.03) with the result that some twin pairs but not others identified foods high in energy density as more pleasant tasting and consumed relatively more energy from them compared to foods low in energy density. These results suggest that there are familial influences on the extent to which high energy density foods are preferred and contribute to total energy intake, and thus provide a potential link between known genetic influences on body fatness and the central role postulated for overeating in weight gain.