If you're already fit and eat a decent amount of protein, boosting your intake even higher with supplements won’t change your muscle, fat, or performance—as long as your workout routine stays the same.

If fit people already eat a lot of protein, taking extra casein protein in the morning or before bed doesn’t change their body fat or muscle over 8 weeks—if their workouts stay the same.

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 you're lifting weights and want to build muscle, eating at least 1.6 grams of protein per kilogram of body weight every day is the biggest factor that helps — more protein means better results, and when you eat it doesn't matter as much.

People who work out a lot, like athletes and bodybuilders, are told to eat more protein than usual to help build muscle, get stronger, and perform better in their sports.