Presentation by Claude Bouchard, M.D., Universite Laval, Quebec, Canada, at AAAS symposium on "Gene-Diet Interactions in Coronary Heart Disease"
There are considerable individual differences in the response to chronic overfeeding for body mass, body composition and a variety of metabolic phenotypes.
We have used an experimental model based on identical twins subjected to treatments lasting for weeks or months to try to identify whether the genes were involved in the heterogeneity in responsiveness. Two overfeeding experiments were undertaken with a total of 18 pairs of young adult male identical twins, and two negative energy balance intervention protocols were executed with the participation of 13 pairs of identical twins.
The results of the most extensive of these experimental protocols are summarized here. Twelve pairs of young adult male monozygotic twins were overfed by 1000 kcal per day, 6 days a week, for a 100-day period. The total excess amount each man consumed was 84,000 kcal. The similarity within each pair in the response to overfeeding was significant with respect to body weight, percent body fat, and subcutaneous fat, with about three times more variance among pairs than within pairs.
After adjustment for the gains in fat mass, the within-pair similarity was particularly evident with respect to the changes in regional fat distribution and amount of abdominal visceral fat with about six times as much variance among pairs as within pairs. The within-pair resemblance for the changes in fasting insulin, insulin response to a glucose load, plasma lipids and lipoproteins was also quite significant but it was reduced when the gains in total body fat were taken into account.
The twins were remeasured 4 months after the overfeeding protocol and again 5
years later. The within-pair resemblance in the post overfeeding changes in
body composition, fat distribution, insulin and plasma lipoprotein levels was
Contact: Cathy Yarbrough
American Heart Association