BASAL FAT OXIDATION DECREASES WITH AGING IN WOMEN

The present study tested the hypothesis that a decrease in basal fat o xidation in aging women is related to a loss of fat-free mass. Thirty- two nonsmoking women with a wide range of age (18-73 yr) were characte rized for body composition (underwater weight), maximal aerobic capaci ty, and basal fat oxidation (indirect calorimetry). Results showed tha t fat oxidation was negatively correlated with age (r(2) = 0.17, P = 0 .017) but was positively correlated with the fat-free mass (r(2) = 0.4 8, P < 0.0001) and with the level of aerobic fitness (maximal aerobic capacity) (r(2) = 0.22, P = 0.007). Unexpectedly, fat oxidation had no relationship with fat mass (r(2) = 0.07, P = 0.136). Partial correlat ion analysis showed that the decline in fat-free mass, and not the age or maximal O-2 consumption, was the best single predictor of the decl ine in basal fat oxidation. These results support the theory that a de crease in fat oxidation with advancing age in healthy women is associa ted with a decrease in the fat-free mass and not age per se. Intervent ions that increase or preserve the quantity of fat-free mass (e.g., ex ercise training) may enhance fat oxidation and thus lessen the age-ass ociated adiposity in women.