Effects of a fat-containing meal on sex hormones in men

The effect of a fat-containing meal on plasma sex steroid concentrations was investigated in normal men. After an overnight fast on two separate occasions, subjects ingested a liquid meal containing either a nonnutritive sweetener (control), or isocaloric meals of mixed calorie sources with either high-fat content or mixed carbohydrate and protein with minimal fat. The order of the meals was alternated. Blood samples were collected at 15-minute intervals and pooled each hour. Sampling began at 7:00 AM and the test meal was ingested at 8:00 AM. Sex steroids, including estrone, estradiol, testosterone, and dihydrotestosterone (DHT), sex hormone-binding globulin (SHBG) capacity, free testosterone concentration, and luteinizing hormone (LH) were determined by either specific radioimmunoassay or dialysis. The fat-containing meal, but not the nonnutritive or mixed carbohydrate and protein meal, resulted in a significant (P less than .01) reduction in total and free testosterone. Estrogens and luteinizing hormone were unaffected by either meal. This is the first documentation, to our knowledge, of the acute effect of a fat-containing meal on sex steroid concentrations in blood. Our observations suggest that a fat-containing meal reduces testosterone concentrations without affecting luteinizing hormone. This might indicate that fatty acids modulate testosterone production by the testes.