If you're a young guy who lifts weights and already eats enough protein, taking extra leucine pills for 12 weeks won't make you stronger or build more muscle in your thighs than just lifting weights by itself.

If you're a young man who lifts weights regularly, eating 1.8 grams of protein per kilogram of your body weight every day is enough to build as much muscle as you can from training—adding extra leucine powder won't help you get any bigger or stronger.

If you're a young man who already lifts weights and eats enough protein, doing strength training twice a week for 12 weeks will make you stronger and build more muscle — and taking leucine supplements won't make any extra difference compared to taking a sugar pill.

If you're a young guy who lifts weights and you take 10 grams of leucine powder split into two doses a day, it won't make you eat more or less protein or leucine from your regular food.

Taking leucine supplements won’t make you stronger in the gym if you’re already a healthy, trained young adult lifting weights—even if you take up to 5 grams a day for a couple of months.

Taking extra leucine — a supplement found in protein — won’t help healthy, fit young adults build more muscle, get stronger, or recover faster from workouts, no matter how much they take or how long they take it, for up to 12 weeks.