Studies of Energy Intake
Fast food is a common subject of such studies.
Cross-sectional studies have established
that individuals consuming fast-food meals
have higher energy intake with lower nutritional
values than those not consuming fast
food.17 Such a finding, however, does not
guarantee that children consuming more fast
food will be more likely to be overweight. In
fact, Cara Ebbeling and several colleagues
find that although both overweight and lean
adolescents consume more calories when eating
fast food, the lean compensate for that energy
intake, while the overweight do not.18 A
recent long-term study of eight- to twelveyear-old
girls did find that those eating fast
food two or more times a week at baseline,
when 96 percent of study subjects were lean,
had larger weight gains at a three-year followup.19
But the study covers only middle-class,
white females. And although its long-term design
makes it more reliable than a crosssectional
study, it still does not conclusively
prove a causal effect of fast food. Unobserved
characteristics of the girls that may be correlated
with both fast-food consumption and
weight gain may be the true causal culprit.