Heritability of hunger relationships with food intake in free-living humans.

The heritability of the before and after meal self-ratings of hunger and thirst and their relationship to food intake was investigated with 110 identical and 102 fraternal same-sex and 53 fraternal mixed-gender adult twin pairs who were paid to maintain 7-day food intake diaries. From the diary reports, the total and meal intakes of food energy and the amounts of the macronutrients ingested were estimated. Subjects rated their subjective levels of hunger on a seven-point scale both before and after eating. Linear structural modeling was applied to investigate the nature and degree of genetic and environmental influences and revealed significant genetic influences on the self-rated levels of hunger both before and after the meals and the change in hunger over the meal. In addition, the relationship between hunger and intake was influenced by the genes. Significant heritabilities were found for the correlations, and the slopes of the regression lines relating before-meal hunger to meal size and also the change in hunger over the meal to intake. This indicates that hunger's effect on intake and, in turn, intake's effects on hunger are to some extent heritable. This suggests that the level of subjective experience and the individuals responses to them are influenced by the genes and become part of the total package of genetically determined physiological, socio/cultural, and psychological processes that regulate energy balance.