When overweight men eat a very low calorie diet for 12 weeks, their testosterone levels go up a lot, which can help improve their health.

The amount of fat consumed in the diet is associated with changes in testosterone levels in the blood, with higher intake between 50 and 150 grams per day linked to higher levels.

Low-carbohydrate, high-fat diets are associated with higher basal testosterone levels compared to high-carbohydrate diets in healthy adults.

In young, healthy men who regularly lift weights, eating a diet high in carbohydrates or high in fat—while maintaining sufficient protein and calories—does not change the levels of testosterone or estradiol in the blood.

Men who ate mostly organic, low-carb Mediterranean food (lots of veggies, nuts, fish, and no junk food) for 3 months had much higher levels of the male hormone testosterone.

If young men eat much less and exercise a lot for four weeks while taking a high dose of testosterone, they gain a few extra kilograms of muscle compared to those taking a fake pill—even though their strength and leg function don’t get better.