You have to eat, except when you're not hungry

In a study of 47 same-sex sibling pairs, the research showed that, even after eating a meal they enjoyed until they were full, overweight and obese children were more prone to overeating when presented with desirable snack foods than their normal-weight siblings.

The study also showed that normal-weight siblings ate less of the meal than their overweight siblings when provided with a calorie-dense appetizer just before the meal. In comparison, overweight and obese siblings did not lessen the amount they ate at the meal enough to offset the additional calories from the appetizer.

"The overweight and obese siblings showed an impaired ability to adjust for calorie differences and consumed more snacks even when satiated," said lead author Tanja Kral, PhD, an assistant professor at Penn Nursing. "These findings suggest some children are less responsive to their internal cues of hunger and fullness and will continue eating even when full."

This inability may be inherited and exacerbated by an environment that offers large portions of desirable foods, said Dr. Kral, explaining that the full siblings in the study were more similar in their eating behaviors more commonly ate more than the half-siblings, suggesting a genetic influence underlying these traits.

In the study, siblings ate a standardized dinner of pasta with tomato sauce, broccoli, unsweetened applesauce, and two percent milk once a week for three weeks. When presented with desirable post-meal snack foods, the overweight and obese siblings ate an average of 93 calories more than their normal-weight siblings. This additional calorie intake over time is considered enough to lead to excess weight gain.

"These findings may represent a behavioral inclination for obesity in children," Dr. Kral said. "Future studies should test whether teaching children to focus on internal satiety cues and structuring the home food environment in a healthy way may prevent at-risk children from overeating."