The purpose of this study was to compare weight-discordant siblings in eating in the absence of hunger, caloric compensation, and the quality of their habitual diet. The investigator hypothesized that, within families and controlling for age differences, overweight and obese siblings would show greater eating in the absence of hunger, poorer caloric compensation, and poorer diet quality (e.g., increased percent of energy from fat and caloric beverages) compared to normal-weight siblings.

The study used a discordant sibling design to compare putative obesity-promoting eating traits among siblings, 5-12 years, who were raised in the same household, but were discordant for weight status (normal-weight: BMI-for-age between 5 and less than the 85th percentile; overweight/obese: BMI-for-age greater or equal to the 85th percentile). Forty-seven pairs of same-sex siblings (boys and girls) were recruited from the greater Philadelphia area to participate in a 4-week study during which their eating behaviors and body composition were assessed. The study tested the hypotheses that overweight/obese, compared to normal-weight, siblings exhibit 1) a weaker ability to compensate for calories, 2) a greater susceptibility towards eating in the absence of hunger, and 3) habitual dietary intakes that favor increased dietary energy density (kcal/g) and increased %energy derived from fat and caloric beverages. The use of a behavioral genetics design to study eating phenotypes among siblings is a unique approach to elucidate shared and non-shared environmental influences that can contribute to variations in weight status during childhood.

Inclusion Criteria:

• same-sex;
• weight discordant (normal-weight vs. overweight/obese);
• meet age criteria;
• like most foods that were served in the study.

Exclusion Criteria:

• serious medical conditions or medication use known to affect appetite, food intake and body weight;
• developmental or psychiatric conditions;
• food allergies or nutrient intolerances (including lactose intolerance).