Live Science is supported by its audience. When you purchase through links on our site, we may earn an affiliate commission. Here’s why you can trust us.

By Anna Gora published 14 July 22

Does protein build muscle? Here are all of your protein questions, answered

Does protein build muscle? The answer to this question is a resounding, ‘yes’. Muscle tissue is composed of a repeating structure of two protein filaments: myosin and actin. Myosin and actin filaments interact with each other to initiate muscle contractions and, over time, mechanical stress caused by constant movement will damage these protein filaments. 

As a result, your muscles need a daily supply of protein to rebuild themselves and stay functional. Mechanical stress from weight training is strenuous enough to make your muscles bigger and stronger, which is why bodybuilders tend to train with extremely heavy weights. It’s also why they may use supplements like the best protein powder and the best protein bars – it’s how they ensure their bodies contain enough protein building blocks to maintain their sculpted physique. 

But it may take more than just drinking protein shakes to achieve the desired musculature. Many different factors affect the strength and size of your muscle fibers, including the type and amount of protein you consume. So if you want to know how protein builds muscle, read on. Here, we’ll discuss the science behind effective bodybuilding and help to answer all of your protein questions. 

The process of constant building and degrading muscle fibers is called muscle protein turnover. If your body is in the so-called anabolic state, your body will build more muscle than it breaks down. If you’re in the so-called catabolic state, you will lose muscle mass. Muscle protein turnover is a relatively slow metabolic process and it takes a while before results become noticeable. As such, the aim of muscle building is to achieve a continuous anabolic state long enough to produce the desired effect. 

According to Frontiers in Nutrition (opens in new tab) , two conditions have to be met for your body to enter an anabolic state: your muscle fibers need to be damaged and your protein intake needs to be sufficient to build new tissue. Resistance training is one of the most effective ways to trigger this state. 

How much muscle you gain through weightlifting will depend on several different factors, including the frequency and intensity of your training sessions. To maximize muscle growth, sports scientists recommend exercising at least twice a week and using weights at 70–90% of one-repetition maximum. One repetition maximum is the heaviest load you can lift, push or pull at one time.

Older people may struggle with muscle building and may lose muscle mass quicker than young individuals. According to an article published in the Journal of Applied Physiology (opens in new tab) , it’s likely to be caused by a blunted response to protein intake. Many studies (opens in new tab) have shown that prolonged sepsis and inflammation could also reduce muscle protein turnover, as well as drinking too much alcohol or not getting enough sleep. 

How much protein you need to build muscle will mostly depend on your body weight and activity levels. Since body weight tends to be the most important factor, recommendations are usually given in grams of protein per each pound or kilogram of body weight. 

However, scientists don’t agree on how much protein is enough. For athletes, the American College of Sports Medicine (opens in new tab) advises eating 1.2-1.4 g of protein per kilogram of body weight to maintain muscle mass and recover from training. The recommendations from The International Society of Sports Nutrition (opens in new tab) are higher – up to 2g grams of protein per kilogram. And according to a meta-analysis published in the British Journal of Sports Medicine (opens in new tab) , eating more than 1.6 g of protein / kilogram will not provide any further benefits. 

It’s worth noting that when it comes to eating protein to build muscle, the quality may be just as important as the quantity. Protein molecules are made out of 20 different amino acids, of which nine are essential, meaning our bodies can’t produce them. To grow new muscle fibers, all of these amino acids need to be present in adequate amounts. 

Animal-based foods are considered complete protein sources because they contain enough of all the amino acids, whereas plant-based sources may not. But you don’t need to eat meat to get protein. If carefully planned, vegan and vegetarian diets can provide the same results, according to the Nutrients (opens in new tab) journal. It’s also been suggested that the branched chain amino acids (BCAAs) leucine, valine and isoleucine could be more effective at building muscle than the others. 

Kwashiorkor is a severe form of protein deficiency that affects millions of people worldwide, mostly in Central Africa and South Asia. In Western nations, some institutionalized older people, hospitalized patients and people on restrictive diets are also at risk of developing this condition. 

The main sign of kwashiorkor is oedema (swelling under the skin) caused by too much fluid in the body's tissues. Other symptoms include loss of muscle mass, an enlarged abdomen, fatty liver and stunted growth. Kwashiorkor is usually a result of famine and humanitarian disasters, and it’s unlikely that it will affect you. However, it’s relatively easy to develop a marginal protein deficiency, especially if you’re on a restrictive diet or suffer from medical conditions. 

So how to recognize that you’re not getting enough protein? Problems with muscle building, unexplained muscle loss and repeated bone fractures are tell-tale signs of a marginal protein deficiency. Other common symptoms include hair thinning, hair loss, brittle nails and skin problems. 

Protein plays multiple roles in the body. It is undoubtedly the main building block – every cell contains some form of this vital macronutrient. It is a core component of muscle and bone tissue, cartilage, red blood cells and skin. Protein is also necessary for the production of enzymes which aid in digesting food and absorbing nutrients. Without this important macronutrient, you may also experience problems with your immunity, hormone balance and wound healing.  

Protein can also be used as a source of energy. It can happen when you’re on a low-carb diet or if you’ve eaten more protein than your body needs. Just like carbohydrates, one gram of this nutrient provides four calories. What’s more, multiple studies (opens in new tab) have shown that increasing your protein intake can help curb your appetite by modifying the levels of important hormones.    

Anna Gora is a Health Writer for Future Plc, working across Coach, Fit&Well, LiveScience, T3, TechRadar and Tom's Guide. She is a certified personal trainer, nutritionist and health coach with nearly 10 years of professional experience. Anna holds a BSc degree in Nutrition from the Warsaw University of Life Sciences, a Master’s degree in Nutrition, Physical Activity & Public Health from the University of Bristol, as well as various health coaching certificates. She is passionate about empowering people to live a healthy lifestyle and promoting the benefits of a plant-based diet.

Stay up to date on the latest science news by signing up for our Essentials newsletter.

Thank you for signing up to Live Science. You will receive a verification email shortly.

There was a problem. Please refresh the page and try again.

Live Science is part of Future US Inc, an international media group and leading digital publisher. Visit our corporate site (opens in new tab) .

© Future US, Inc. Full 7th Floor, 130 West 42nd Street, New York, NY 10036.