A critique of the scientific validity of the dietary advice in Men’s Health magazine discovered nuggets claiming meat can give men “a testosterone boost,” but we’ve known for a quarter century that a meal with that much fat can drop testosterone levels by nearly one-third within hours. In fact, a significant drop of both free and bound testosterone in the bloodstream occurs within just one hour of it going in one’s mouth, whereas a low-fat meal of mostly carbs has no such effect. Based on in vitro studies on the effects of fat on testicle cells in a petri dish, researchers suspect fat in the blood may actually suppress testosterone production in real time. If you feed people lots of eggs and meat, including fish and poultry, and then switch them to a diet with bread, fruit, vegetables, and sugar—but about the same amount of fat—all their testosterone levels go up. Even more importantly, however, all their levels of cortisol, a stress hormone produced by our adrenal glands, go down