The heritability of nutrient intake was investigated with 109 identica
l and 86 fraternal adult twin pairs who were paid to maintain 7-day fo
od intake diaries. Both classical analysis of heritability and linear
structural modeling revealed significant additive genetic influences o
n body size, height and weight, and body fatness (body-mass index). Si
gnificant heritabilities were also found for the amount of food energy
ingested daily, as well as its macronutrient, alcohol, and water cont
ent. Linear structural modeling analysis showed that 65% of the varian
ce in energy intake was attributable to heredity. In addition, the pat
tern of intake, meal frequency, size, and meal macronutrient, alcohol,
and water composition, were also found to have strong heritabilities.
Linear structural modeling indicated that 44% of the variance in meal
frequency and 65% of the variance in meal size was attributable to he
redity. However, shared, familial environment had no significant impac
t on the levels or pattern of intake in adulthood. These results indic
ate that not only body size but also the pattern and amounts of nutrie
nts ingested by humans in natural environments are strongly influenced
by the immediate environment and heredity, but not at all by the fami
lial environment.