Familial aggregation of amount and distribution of subcutaneous fat and their responses to exercise training in the HERITAGE Family Study

Objective: Investigate the familial aggregation of amount and distribution of subcutaneous fat and their changes in response to endurance training. Research Methods and Procedures: A total of 483 sedentary subjects from 99 nuclear families were recruited, trained for 20 weeks of exercising on cycl e ergometers, and measured before and after training for the following indi cators of subcutaneous fat and fat distribution: trunk fat (TRUNK = sum of abdominal, subscapular, suprailiac, and midaxillary skinfolds), extremity f at (EXTREM = sum of biceps, triceps, thigh, and calf skinfolds), subcutaneo us fat (SF8 = sum of the eight skinfolds), the trunk to extremity skinfolds ratio adjusted for SF8 (TER) and waist girth adjusted for body mass index (WAIST). The familial aggregation of the age- and sex-adjusted baseline phe notypes and their responses to training (Delta) after adjustment for the ba seline values was investigated using a familial correlation model. Results: Significant familial aggregation was observed for all the phenotyp es measured at baseline and for Delta TRUNK and Delta WAIST. Transmissibili ty estimates reached about 30% to 35% for TRUNK, EXTREM, and SF8 and 50% fo r TER and WAIST. The transmissibilities of the response phenotypes were low er, ranging from 0% for Delta WAIST to 21% for Delta TRUNK and the pattern of familial correlations suggested a greater within- than between-generatio n resemblance in the response. Discussion: This study suggests that the amount and distribution of subcuta neous fat strongly aggregates in families, whereas the response to exercise training is characterized by a moderate and more complex pattern of famili al resemblance. We conclude that familial/genetic factors are more importan t in determining the amount and distribution of subcutaneous fat than their responses to exercise training.