Eating high-fat foods may reduce free testosterone levels according to one study that measured serum levels of sex steroid hormones after ingestion of different types of food. High-protein and high-carbohydrate meals had no effect on serum hormone levels, but a fat-containing meal reduced free testosterone levels for 4 hours (Killinger et. al. 1987)....... (in men).

The resulting hormone imbalance (too much estrogen and not enough free testosterone) in obese men partially explains why so many are impotent and experience a wide range of premature degenerative diseases (Blum et al. 1988).