In young men who lift weights recreationally, eating more than 2.0 grams of protein per kilogram of body weight per day led to slightly greater increases in strength over 8 weeks compared to eating less, even though muscle size increased similarly in both groups. This suggests that strength gains may come from improvements in how the nervous system controls muscles or in lifting technique, rather than just from muscle growth.

Young men who lift weights for muscle growth and eat more than 2.0 grams of protein per kilogram of body weight each day tend to get stronger on average than those who eat less than that amount, based on improvements in their squat, bench press, and deadlift numbers over 8 weeks.

If guys who already lift weights drink a 20g protein shake after working out for 9 weeks, they’ll gain more muscle and get stronger—even if the protein is a mix of fast- and slow-digesting types.

For young men who exercise regularly, eating more than 2.0 grams of protein per kilogram of body weight per day does not lead to significantly more muscle gain than eating less than that amount over an 8-week resistance training program.

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.

Older guys between 60 and 75 who aren't very active can get a lot stronger in just 12 weeks by lifting weights twice a week—even if they don’t take extra protein right after workouts or before bed, as long as they’re already eating enough protein overall.