Protein is probably the most important macronutrient to focus on getting enough of if your goal is weight loss and boosting your metabolism. Although protein isn’t a primary source of energy like carbohydrates and fat, protein is needed to create the structures in your body and support many of your body’s functions including building lean body mass, which increases your resting metabolic rate. Protein is also needed to maintain healthy skin hair, and nails, as well as to make all your hormones and enzymes.
Types of Protein
Proteins are made of up chains of amino acids. There are 20 amino acids that the human body requires to do all its functions.
Essential amino acids are amino acids that your body can’t synthesize on its own so you need to obtain those in your diet. There are nine essential amino acids including three branched-chain amino acids (leucine, isoleucine, and valine). Branched-chain amino acids (BCAAs) are abundant in your muscles which is why you may see people taking BCAA powders during or after workouts to help build muscle and enhance exercise performance.
The remaining 11 amino acids are non-essential amino acids that the body can synthesize on its own so it’s not necessary that you obtain them in your diet.
When you don’t have sufficient reserves of glucose in your liver and muscles to maintain blood sugar levels and provide energy for movement, the body can use protein to provide energy, but you don’t want this if you’re trying to boost your metabolism. Glucogenic amino acids can be converted into glucose for energy and ketogenic amino acids can be converted into ketone bodies for energy. However, using amino acids for energy requires breaking down tissue in the body that contains amino acids, which is mainly muscle. If you lose muscle mass your resting metabolic rate decreases, so if you start breaking down your muscles to provide energy, you’re also slowing your metabolism.
How Much Protein Do You Need?
The Recommended Dietary Allowance (RDA) for protein is kind of low; it’s 46 grams per day for women and 56 grams per day for men, which is based on using 0.8 g of protein per kg of body weight. That’s enough to prevent any protein deficiencies, but not enough to promote sustainable fat loss or to boost your metabolism.
Research has shown that eating 25-30% of your total calories from protein has been linked with significant weight loss, appetite reduction, and a boost in resting metabolic rate.(ref) If you were eating 2,000 calories per day, for example, that would translate to 125-150 grams of protein per day. That higher amount of protein will help you to build muscle and keep you satiated between meals so you ultimately consume fewer calories. Aim to get at least 20–30 grams of protein per meal to minimize your hunger between meals.
Animal-Based Versus Plant-Based Protein
Animal protein includes poultry, seafood, meat, eggs, and dairy. Animal proteins are complete proteins, meaning that they contain all the essential amino acids. It’s very easy to consume at least 20-30 grams of protein in a meal eating animal-based proteins, but you need to watch the amount of fat that you’re consuming from these foods. Make sure that some of your animal-based proteins come from leaner sources such as poultry, lean red meat, low-fat dairy, lean fish and seafood, and egg whites. You absolutely need some fat in your meals, but you want to keep your intake more moderate if you’re trying to lose weight.
Plant-based sources of protein include legumes, some whole grains, nuts, and seeds. With the exception of soybeans, plant-based proteins are incomplete proteins because they are missing one or more essential amino acids. So if you’re getting most or all of your protein from plant-based sources you just need to make sure that you’re eating a variety of foods so that you consume all your essential amino acids. This should not be an issue if you’re eating a diet of mostly whole foods.
Something that you do need to consider with plant-based proteins, however, is that they come from foods that also have a high starch or fat content. For example, a 1/2 cup of black beans contains 7 grams of protein and 23 grams of carbohydrates. Although those carbohydrates include 6 grams of fiber, to get 20 grams of protein from beans in a single meal you would need to eat 1.5 cups of beans, which provide over 60 grams of carbohydrates. Therefore, if legumes are your main source of protein in a meal, you should be counting those as the starch for your meal as well.
If you’re getting some of your protein from nuts and seeds, also count those foods as a serving of fat. The 8 grams of protein in a 2 tablespoon serving of peanut butter comes with 16 grams of fat so nuts and seeds probably shouldn’t be used as a primary source of protein if your goal is weight loss.
Overall, if you’re trying to boost your metabolism, protein should be the first macronutrient that you focus on getting sufficient quantities of in each meal. Eating at least 20 grams of protein per meal will help keep you full and provide you with the building blocks to create more lean muscle mass and ultimately increase your metabolism.