Effect of Changes in Fat Distribution on the Rates of Change of Insulin Response in Children

Objective: To develop mixed models for examining longitudinal associations between rates of change in visceral, subcutaneous abdominal, and total body fat with rates of change in fasting insulin (FI) and insulin sensitivity (SI) over 3 years in children. Research Methods and Procedures: Seventy-seven children (mean age, 8.3 years at baseline) from Birmingham, Alabama, with three or more annual measures of FI and SI were included. Abdominal fat was measured by computed tomography, and total body fat and lean tissue mass were measured by DXA. Mixed models examined the longitudinal associations between the baseline level/rate of change of different fat compartments and the rate of change in FI or SI. Results: An annual increase of ∼5% in FI was associated with 1 cm²/yr of visceral fat gain per year (p < 0.05), independent of subcutaneous abdominal fat. A 1-cm² difference in initial subcutaneous abdominal fat was associated with an ∼0.2% increase per year in FI (p < 0.02), independent of visceral fat. None of the rates of change in any of the fat measures was associated with the rate of change of SI. Discussion: The rate of change in visceral fat was positively associated with the rate of change in FI, independent of increasing subcutaneous abdominal fat; however, subcutaneous abdominal fat may be more predictive of the rate of change of FI than visceral or total fat. Therefore, growth-related increases in abdominal fat, particularly subcutaneous abdominal fat, may contribute to accelerating increases in FI, but have no effect on SI.