Dieting, exercise, or disordered eating does not account for extremes of 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 project to identify genes for human obesity.


METHODS
Ninety-nine Caucasian families were selected for study because they contained both extremely obese and average-weight family members. Family members (n=492) were queried about their diet and exercise habits, 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 average body weights in these families did not appear to be maintaining their weight by dieting and <4% of the average-weight subjects had ever been obese in the past.


CONCLUSIONS
Although dieting and other weight loss practices potentially could either mask or complicate the genotype-phenotype relationship, we found little evidence for this possibility in the families studied.
Reed
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Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania, Philadelphia 19104, USA.
Price
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D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001835:Body Weight; D004038:Diet, Reducing; D015444:Exercise; D005190:Family; D001068:Feeding and Eating Disorders; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000235:genetics*; D015431:Weight Loss