6. Why Protein Is Important and Drives Your Metabolism

The Benefits of a Protein-Centric Diet on Metabolism

Many people have heard but few truly understand why protein is important and fail to grasp the deeper concept that it does drive your metabolism. Higher protein diets have multiple positive effects on body composition and especially your muscle metabolism. That is why higher protein diets are particularly beneficial during weight loss, they accelerate fat loss while protecting lean muscle tissues, including organs and muscles.

Higher protein diets enhance satiety. They reduce feelings of hunger and the desire for snacking making it easier to control your calorie intake. Protein also generates higher energy expenditure compared with carbohydrates or fats and substituting protein for carbohydrates and reduces stress on insulin production and improve regulation of blood sugar, which is critical for controlling and preventing diabetes. You can see the incredible benefits of why protein is important….a protein-centric diet energizes your metabolism.

The Trigger for Muscle Metabolism 

Underlying each of these benefits of protein is the essential amino acids is called leucine. Leucine is an important amino acid making up 8% to 10% of virtually every protein in the body. In mother’s milk, leucine makes up almost 12% of the amino acids in proteins for the baby. Beyond its role in the structure of proteins, it has important metabolic roles in energy metabolism, regulation of insulin, use of blood glucose, and stimulation of protein synthesis in muscle. The amount of leucine in your blood reflects the amount of protein in each meal and the body recognizes the changes in leucine as a signal of diet quality.

During the late 1990’s, my research group made an incredible discovery…that the amount of leucine in a meal provided a unique metabolic signal for regulation of muscle protein synthesis (MPS). In children, muscle growth is regulated by hormones including growth hormone and insulin, but in adults, maintenance of muscle is determined by exercise and dietary protein. We now know that triggering MPS requires meals that contain approximately 3.0 grams of leucine. This amount of leucine will cause a rapid increase in the amount of leucine within muscle and that serves as a single to the muscle that the diet has enough protein to support MPS. Let’s go into a bit more depth about this role of leucine.

The Importance of Muscle Metabolism

After a meal containing protein, the body begins to digest the protein and absorb the individual amino acids. The leucine present in the protein begins to appear in the blood. The amount of leucine in the blood increases, and the amount of the increase is directly related to the amount of protein in the meal. In most meals, leucine accounts for 8% to 10% of the protein. The increased level of leucine will trigger insulin release by the pancreas which helps all cells use both blood sugar and amino acids. In muscle, the leucine triggers a unique regulatory protein called “mTOR” which signals the muscle to build new proteins. The leucine also signals the mitochondria to burn more fatty acids which supplies the ATP fuel necessary for muscle protein synthesis (MPS). This meal effect of leucine produces an anabolic response in muscle that helps muscle repair, replace, and remodel existing proteins. This process of is essential for your muscles to remain healthy. Trigger your msucle metabolism becomes increasing important as we get older and is critically important during catabolic periods of weight loss, illness, or injury.

How to Sustain Muscle Metabolism

It is also important to understand that this anabolic period only occurs after a meal that contains at least 3.0 grams of leucine and it only lasts for about 2 hours. To translate the 3.0 grams of leucine into your need for dietary protein, remember protein typically contains 8% to 10% leucine, so you would need 30 to 36 grams of protein at a meal to provide enough leucine to trigger the MPS response. This short-term meal-response also means that to maintain muscle health, we need at least two or three protein meals each day.

Eating More Protein Burns More Calories Than Other Foods

One additional benefit of the meal-response to protein is the energy expenditure. MPS requires significant amounts of calories or ATP. After a protein-rich meal, you often feel warmer. This is called a Thermic Effect for Food (TEF). This TEF food is generally thought to be associated with the digestion, absorption, and metabolism of food, but for protein it directly relates to the energy costs of MPS. Because of the unique metabolic roles of protein, the TEF for protein is 15% to 20% while TEF for carbohydrates and fats is only 5%. That means, if the nutrient label says the food has 100 calories from protein, you lose 20 calories as heat (or TEF) and only really get 80 calories. But with carbohydrates, 100 calories yields 95 calories. This is an important benefit of protein in a weight loss diet. Simply by replacing carbohydrates or fats with protein you will increase calorie expenditure and help with weight loss.

Protein-centric diets are critical for adults to maintain muscle health as they age and naturally lose muscle health, but also essential during weight loss to enhance loss of body fat while protecting your lean body mass including vital organs.