If young guys who don't usually lift weights eat about 1.6 grams of protein per kilo of body weight every day—whether from plant-based foods and soy protein or from regular mixed diets with whey—they can get noticeably stronger in their legs after 12 weeks of weight training.

If young adults who aren't used to working out eat a bit more protein—especially from whey or soy—and lift weights 3 times a week for 3 months, they’ll likely gain more muscle and get stronger, even if they weren’t eating enough protein to start with.

If young guys who don’t work out much eat a plant-based or meat-based diet with the same amount of protein and lift weights for 12 weeks, they’ll gain about the same amount of leg muscle and strength.

If female college athletes who lift weights drink a protein shake with 24 grams of protein before and after workouts for eight weeks, they’ll get stronger in their upper body — especially if they use whey protein instead of casein.

For young guys lifting weights, eating 1.8 grams of protein per kilo of body weight each day is enough to gain muscle and get stronger in 10 weeks — it doesn’t matter if they take a 35g casein protein shake during the day or before bed.

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.