Importance for building muscle
Protein is important for building muscle. But you could eat 100% of your calories from protein, and you won’t gain an ounce of muscle if your daily total calorie intake isn’t greater than your daily calorie output.
To build muscle, you require a balanced diet that provides approximately 300-500 more calories than your maintenance calorie intake level. All the protein you require to build extra muscle will be contained in this amount of food, provided your diet is balanced properly.
A diet that provides 10%-15% of calories from protein is all that is required to grow muscle.
Consider this: Infancy is the time of a human’s life when growth is the most rapid, and when protein needs are the highest. Yet, human breast milk contains only 10% protein by calories (versus about 30% for cow’s milk). This is more than adequate to meet the needs of a growing human infant who doubles its weight in 6 months and triples its weight in a year.
You aren’t going to grow new lean tissue nearly as fast, (0.5-2.5 pounds a week) so forget about stuffing yourself with protein…just eat a balanced diet. Besides, when your protein intake is too high, you crowd out other calorie-dense foods from your diet that are needed to provide energy, and that spare protein for growth. Why do you think people lose weight on a high-protein diet?
How does exercise affect my protein requirement?
Numerous studies involving both endurance and strength exercise have shown that the current recommended protein intake of 0.75 g/kg body weight/day is inadequate for people who participate in regular exercise or sport. Additional protein is needed to compensate for the increased breakdown of protein during and immediately after exercise, and to facilitate repair and growth. Exercise triggers the activation of an enzyme that oxidises key amino acids in the muscle, which are then used as a fuel source. The greater the exercise intensity and the longer the duration of exercise, the more protein is broken down for fuel.
In addition, dietary protein provides an enhanced stimulus for muscle growth. To build muscle, you must be in ‘positive nitrogen balance’. This means the body is retaining more dietary protein than is excreted or used as fuel. A sub-optimal intake of protein will result in slower gains in strength, size and mass, or even muscle loss, despite hard training. In practice the body is capable of adapting to slight variations in protein intake. It becomes more efficient in recycling amino acids during protein metabolism if your intake falls over a period of time. The body car also adapt to a consistently high protein intake by oxidising surplus amino acids for energy.
It is important to understand that a high protein diet alone will not result in increased strength or muscle size. These goals can only be achieved when an optimal protein intake is combined with heavy resistance (strength) training.
How much protein do I need for maximum performance?
For an endurance athlete, the recommended range is 1.2-1.4 g/kg body weight/day (Lemon, 1998; Williams & Devlin, 1992; Williams, 1998; ACSM, 2000).
Many recent studies show that strength and power athletes have a greater daily requirement for protein than most endurance athletes. The current consensus recommendation is an intake between 1.4 and 1.8 g/kg body weight/day (Williams, 1998; Tarnopolsky et al., 1992; Lemon et al., 1992). The American Dietetic Association and ACSM recommend 1.6-1.7 g/ kg body weight per day. So, for example, a distance runner weighing 70 kg would need 84-98 g/day. A sprinter or body-builder with the same body weight would need 98-126 g/day.
In practice, protein intakes generally reflect total calorie intake, which is why the International Consensus Conference on Foods, Nutrition and Performance in Lausanne (1991) stated that protein should comprise 12-15% of total energy intake. This assumes that your calorie intake matches your calorie requirements.