DIETING, EXERCISE, OR DISORDERED EATING DOES NOT ACCOUNT FOR EXTREMESOF BODY-WEIGHT WITHIN FAMILIES

Objective: Families having both members with obesity and thin members should contain substantial information for genetics studies, provided measured phenotype is an accurate indicator of genetic predisposition. We assessed the impact of potentially complicating behavioral factors on obesity phenotypes of family members selected for a long-term proj ect to identify genes for human obesity.Research Methods and Procedure s: Ninety-nine Caucasian families were selected for study because they contained both extremely obese and average-weight family members. Fam ily members (n = 492) were queried about their diet and exercise habit s, their psychiatric histories as they pertained to eating disorders, and for a subset of subjects (n = 329), a lifetime dieting history and a lifetime maximum weight were recorded. Results: Subjects with avera ge body weights in these families did not appear to be maintaining the ir weight by dieting and <4% of the average-weight subjects had ever b een obese in the past. Discussion: Although dieting and other weight l oss practices potentially could either mask or complicate the genotype -phenotype relationship, we found little evidence for this possibility in the families studied.