Effects of Diet and Exercise on Leptin Levels In Women

Abstract

0531 Leptin is strongly associated with body composition parameters, and some studies show significant associations with energy expenditure. Few prospective diet and exercise studies have determined whether changes in leptin parallel indices of body composition, changes in dietary intake, or changes in energy expenditure. PURPOSE: Because leptin is a key metabolic signal involved in energy homeostasis and reproductive function, the association between changes in leptin and changes in other metabolic parameters was examined in a large prospective study on exercise on the menstrual cycle. METHODS: 53 sedentary, normal weight, college age women were randomly assigned to control or exercise groups for a three month controlled feeding and exercise study. Screening confirmed ovulatory status and absence of factors that impact reproductive or metabolic status. A control cycle and then 3 cycles where exercise and feeding occurred were monitored. Aerobic exercise and diet were prescribed as kcals of a % of eucaloric intake. Groups were “clamped” at 5 levels of energy balance. Controls remained eucaloric and did no exercise. Three of four exercise groups were in energy deficits ranging from−15 % to – 60 % of eucaloric intake and in one food was increased to achieve energy balance (0%). Training was 5 × per wk. Serial measurements of body weight (2 × per week), body composition, metabolic hormones, energy expenditure components, VO2max, stress, and reproductive hormones were performed. RESULTS: Leptin correlated at baseline (n = 53; p<0.05 for all) with age (r = −.33), age of menarche (r = −.31), % fat (r = .611), weight (r = .50), fat mass (r = .63), and BMI (r = .49), but not eucaloric intake (kcals), resting metabolic rate (kcal/min), physical activity energy expenditure (kcals), or RQ (p > 0.05 for all). In the 41 subjects that completed the study, leptin, body weight, and fat mass, and body weight declined significantly (Leptin = 10.0 ± 4.8 to 8.0 ± 4.0 ng/ml; p < 0.05; ANOVA); significant correlations between the change in leptin and the changes in other parameters were BMI (r = .48; p<0.002), weight (r = .50; p < 0.002) and fat mass (r = .33; p <0.04). No significant relationships existed between baseline leptin, changes in leptin, and baseline or changes in energy expenditure parameters. CONCLUSION: Decreases in leptin after a diet and exercise intervention closely parallel changes in body composition but not energy expenditure or food intake. Modulation of chronic leptin levels is driven by energy stores; a role for leptin in modulation of energy expenditure is not supported. Supported by NIH RO1 AR3945–01 and MO1 RR 10732.