It's a common belief that when you exercise you need to eat extra protein, or that eating more protein will help you build more muscle. However, neither of these ideas is strictly true.
Protein bars and protein powders are a major feature of many gyms, and of advertisements for buff bodies. But according to The Institute of Medicine's Dietary Reference Intakes Report, "In view of the lack of compelling evidence to the contrary, no additional dietary protein is suggested for healthy adults undertaking resistance or enduring exercise."
Of course, if you're exercising a lot, you do need to eat more calories, which means you get more protein – but there's still no reason to get more than 10 to 35 percent of your calories from protein.
Excess protein won't help to build bigger muscles either. Any extra protein you get is simply converted to, and stored as, fat. Carbohydrates are actually the best form of “fuel” for muscles exercised for long periods. In fact, a diet high in protein and fat, but low in carbohydrates, can impair athletic performance.
CalorieKing recommends a calorie-controlled diet in which carbohydrates make up around 45 to 65 percent of total calories, fat makes up 20 to 35 percent of total calories, and protein around 10 to 35 percent of total calories. If you are exercising intensely, it's a good idea to speak to a sports nutritionist about your nutritional goals.