To validate our hypothesis that reduction in dietary fat may result in changes in androgen metabolism, 39 middle-aged, white, healthy men (50-60 yr of age) were studied while they were consuming their usual high-fat, low-fiber diet and after 8 wk modulation to an isocaloric low-fat, high-fiber diet. Mean body weight decreased by 1 kg, whereas total caloric intake, energy expenditure, and activity index were not changed. After diet modulation, mean serum testosterone (T) concentration fell (P < 0.0001), accompanied by small but significant decreases in serum free T (P = 0.0045), 5 alpha-dihydrotestosterone (P = 0.0053), and adrenal androgens (androstendione, P = 0.0135; dehydroepiandrosterone sulfate, P = 0.0011). Serum estradiol and SHBG showed smaller decreases. Parallel decreases in urinary excretion of some testicular and adrenal androgens were demonstrated. Metabolic clearance rates of T were not changed, and production rates for T showed a downward trend while on low-fat diet modulation. We conclude that reduction in dietary fat intake (and increase in fiber) results in 12% consistent lowering of circulating androgen levels without changing the clearance.

OBJECTIVE: In healthy, nonobese, adolescent males and females to: (1) Determine the relationship between ®tness and energy intake; (2) assess the effect of ®ve-weeks endurance training on energy intake and food choice and (3) compare food record assessments of energy intake with doubly-labeled water (DLW) measurement of total energy expenditure (TEE). DESIGN: (1) Cross sectional analysis of ®tness and food intake and (2) Prospective, randomized, controlled interventional study of endurance-type exercise training in 44 females and 44 males (age range, 15±17 y). MEASUREMENTS: Pre and end interventional three day food records were successfully collected from 32 females (15 controls, 17 trained) and 39 males (19 controls, 20 trained). Fitness was assessed from cycle ergometry as peak oxygen uptake normalized both to thigh muscle mass and body weight. Thigh muscle mass was measured by magnetic resonance imaging. TEE using the DLW technique was measured in 12 females (6 controls, 6 trained) and 20 males (10 controls, 10 trained) during weeks 4±5 of the exercise training program (simultaneously with the second assessment of food records). Food record data were analyzed using the Minnesota Nutrition Data System. RESULTS: Fitness was correlated with self reported total caloric intake in males but not females. In females, there was a signi®cant increase in fat intake (19.8 AE 9%, P`0.05) and a signi®cant decrease in carbohydrate intake (79.8 AE 4%) in the trained subjects. No changes were observed in the control subjects. Energy expenditure (2072 AE 52 kcalad) was signi®cantly greater than the estimated energy intake (1520 AE 112 kcalad, P`0.007) during the intervention in the trained, but not control, subjects. However, there was no weight change in either control or trained subjects. In males, no changes were observed in food choice in either control or trained subjects. Similar to the females, energy expenditure (2425 AE 22 kcalad) was signi®cantly greater than the estimated energy intake (2168 AE 117 kcalad, P`0.05) during the intervention in the trained, but not control, subjects. No weight changes were observed in either group. CONCLUSIONS: Fitness is associated with increased self-reported energy intake in males but not females, while exercise training led to alterations in food selection (greater fat and reduced carbohydrate) only in females. These observations could re¯ect speci®c gender differences, or, alternatively, the generally lower levels of ®tness in the females. The apparent negative energy balance without evidence for weight loss in both the trained males and females suggests a systematic under reporting of food intake during exercise programs in adolescents, and indicates the possibility that errors in self reported food intake might be greater during transitions from one level of energy expenditure to another.