INSULIN SENSITIVITY CHANGES WITH AGING, ABDOMINAL ADIPOSITY, AND AEROBIC BUT NOT RESISTANCE TRAINING

Abstract

Insulin sensitivity (Si) has been shown to improve following aerobic (AT) or resistance (RT) training in young subjects but little is known about the change in Si with aging or how AT or RT affects Si in older subjects. To address these questions, Si was measured in 143 untrained, apparently healthy, non-diabetic men and women aged 22–87 y who were randomized either to 12 weeks of progressive exercise (RT or AT) or control (stretching) activity. After receiving standardized meals for 3 days, Si was assessed using the intravenous minimal model technique. At baseline there was a significant decline in Si with aging (r = −0.33, p < 0.01). However, total abdominal fat content, as determined by CT scan, was a superior correlate with Si (r = −0.70, p < 0.01). Multiple regression analysis revealed that after abdominal fat was included, the model describing the variability in Si was not significantly improved by the addition of age or other variables such as gender, VO2max, total fat mass, fat-free mass or fasting insulin and glucose levels. RT (n = 23) performed by middle-aged (45 y) and older (65 y) adults resulted in significant strength gains (25%, p < 0.01) but Si was unchanged. Si was also unchanged in controls (n = 59). In contrast, AT (n = 60, age range 22–87 y) lead in improvements in VO2max (11%, p < 0.01) and Si (27%, p < 0.01). AT was also associated with a 10% decrease in abdominal fat (p < 0.02). These changes in the AT group were similar among men and women of all ages. We conclude that although insulin sensitivity appears to decline with age, it is more closely related to abdominal adiposity. Additionally, insulin sensitivity is significantly improved following aerobic training, but not resistance training in middle-aged and older adults. Supported by NIH RO1 AG09531 and MO1 RR00585.