PHYSIOLOGICAL PREDICTORS OF INCREASING TOTAL AND CENTRAL ADIPOSITY INAGING MEN AND WOMEN

Background: Increasing levels of total and central body fat with advan cing age contribute to the development of cardiovascular and metabolic disease. We examined gender-related differences and physiological pre dictors of the rate of increase in total and central body fat in men a nd women. Methods: We studied 427 healthy men (age range, 17 to 90 yea rs) and 293 women (age range, 18 to 88 years). We measured body fatnes s by hydrostatic weighing, central adiposity from the waist circumfere nce, peak volume of oxygen utilization (Vo(2)) from a treadmill test, leisure time physical activity (LTA) from a questionnaire, resting met abolic rate and respiratory quotient from indirect calorimetry, and en ergy intake from 3-day food diaries. Results: Fat mass increased with age, and the rate was greater in women (r=.61; slope=0:25 kg/y; P<.01) than in men (r=.43; slope=0.16 kg/y; P<.01). Increasing fat mass in m en and women was most strongly associated with declines in peak Vo(2) and LTA. Controlling for these variables reduced the increase in fat m ass from 17% to 3% per decade in men and from 26% to 5% per decade in women. The increase in waist circumference with age was also greater i n women (r=.53; slope=0.28 cm/y) than in men (r=.39; slope=0.18 cm/y; P<.01). Increasing waist circumference with age in men and women was m ost strongly associated with declines in LTA and peak Vo(2), respectiv ely. Control for these variables reduced the age-related increase in w aist circumference from 2% to 1% per decade in men and from 4% to 1% p er decade in women. We observed no independent contribution of resting metabolic rate, respiratory quotient, menopause status, energy, or ma cronutrient intake to the age-related increase in fat mass and waist c ircumference. Conclusions: Our findings suggest that (1) the age-relat ed increase in fat mass and waist circumference is greater in women th an in men and (2) the physiological characteristics that reflect a dec line in physical activity-related energy expenditure, rather than rest ing energy expenditure, are important predictors of the increases in t otal and central fatness. Lifestyle changes that increase the level of physical activity may be advantageous in blunting age-related increas es in total and central body fatness.