Does More Protein in Strength Training Adults Lead to Greater Strength?


More Protein

Can upping your protein boost muscle growth and strength gains? Bodybuilders sometimes adopt a high-protein diet, hoping to build more muscle or becoming even stronger. Protein and bodybuilding go together, right? But does this approach work? Protein provides amino acids, which are the building blocks for muscle tissue. Without sufficient amino acids, muscles cannot grow larger or perform better. As a result, resistance training isn’t as effective.

While it is true that you need adequate quantities of protein to build muscle and maintain an anabolic state, there are limitations to consuming more protein. A new study finds that beyond a certain quantity, consuming more protein doesn’t lead to greater gains in muscle strength or size. This study calls into question the wisdom of eating large quantities of protein to build muscle.

What the Study Showed

In a study published in the American Journal of Physiology, Endocrinology, and Metabolism, researchers asked 50 middle-aged adults (ages 40-64) to take part in a 10-week strength training program. Beforehand, they checked multiple measures of health and fitness, including BMI, lean body mass, glucose levels, and blood pressure on the participants.

They also analyzed the participants’ gut microbiome, the composition of gut bacteria that live in their gut. These bacteria are sensitive to diet and also affect factors such as body weight, immune health, nutrient absorption, and more.

The groups trained similarly, but their diets differed. One group ate a moderate protein diet during their training, around 1.2 grams of protein per kilogram of body weight. The other ate a high protein diet, consisting of 1.6 grams of protein per kilogram of body weight. The high-protein diet was about twice what experts recommend for a sedentary person. However, people who work out sustain more muscle damage and need more protein than a sedentary protein. The participants ate high-protein meals but also drank protein drinks in the evening.

By now you’re probably wondering whether the group who ate a higher protein diet gained more strength or muscle mass. They didn’t. In fact, there were no significant differences between the two groups in terms of muscle strength, muscle gains, body fat, or body composition. Other markers of health such as glucose control and blood pressure were similar too.

There was one worrying change in the high-protein group. The participants who consumed 1.6 grams of protein per kilogram of body weight daily experienced concerning changes in their gut microbiome. The populations of bacteria linked with worse health outcomes increased in the group who ate the higher protein diet during their training. However, strength training seemed to reverse some of these effects. Gut bacteria are affected by what we eat, as they thrive on fiber-rich foods. Animal-based protein sources lack fiber, so if you get more of your protein from animal foods, it can change your gut microbiome and not for the better.

Are There Other Benefits of Consuming a Higher Protein Diet?

If you’re trying to lose weight, eating more protein helps with satiety. Protein-rich foods activate appetite-suppressing hormones more than fats or carbohydrates. Plus, eating protein causes a greater boosting in metabolic rate than eating carbohydrates or fats. These factors may help if you’re trying to get leaner. Some studies show that dieters who eat a high-protein diet lose more weight than those who consume a diet lower in protein. Though more protein may not boost your strength or muscle gains, it could help you get leaner.

You Also Need Carbohydrates After a Workout

There’s another macronutrient you need, beyond protein, after a workout, and that’s carbohydrates. Research reveals that consuming carbohydrates after exercise promotes better muscle recovery than consuming protein alone. After an intense strength training or aerobic workout, muscles are depleted of their primary energy source – glycogen. A carbohydrate snack helps replenish glycogen stores for a faster recovery. You’ll feel less fatigued and your muscles will recover faster if you eat a post-workout snack with a ratio of protein to carbohydrates of around 3 to 1.

The Bottom Line

You need “enough” protein to build muscle, but consuming more, beyond a certain threshold, won’t strengthen you or build more muscle. Consuming over 1.2 grams of protein per kilogram of body weight may not boost your gains and could have adverse effects on your gut microbiome. This is only one study, but it suggests that more isn’t always better with respect to protein.

However, if you do very intense workouts or are over the age of 60, you may need a higher protein intake. Older adults have anabolic resistance where their muscle-building machinery doesn’t turn on as easily as a younger person’s. Some studies suggest that getting more protein and taking fish oil supplements my counter anabolic resistance and be of benefit for older adults.

The take-home message? Eat a balanced diet and make sure you’re getting around 1.2 grams of protein per kilogram of body weight each day but there may not be a point to getting more. Choose nutrient-dense foods that will support your training and eliminate empty calories from sources like sugar and refined carbohydrates. Also, you don’t necessarily need a protein supplement or shakes to get enough protein. Balance your diet with other measures that support muscle growth like plenty of sleep and stress management. These are changes all athletes should make to improve their health and maximize their training gains.



  • Colleen F. McKenna, Amadeo F. Salvador, Riley L Hughes, Susannah E. Scaroni, Rafael A. Alamilla, Andrew T Askow, Scott A. Paluska, Anna C Dilger, Hannah D. Holscher, Michael De Lisio, Naiman A Khan, Nicholas A. Burd. Higher protein intake during resistance training does not potentiate strength, but modulates gut microbiota, in middle-aged adults: a randomized control trial. American Journal of Physiology-Endocrinology and Metabolism, 2021; DOI: 10.1152/ajpendo.00574.2020.
  • Pesta DH, Samuel VT. A high-protein diet for reducing body fat: mechanisms and possible caveats. Nutr Metab (Lond). 2014;11(1):53. Published 2014 Nov 19. doi:10.1186/1743-7075-11-53.
  • Campos-Nonato I, Hernandez L, Barquera S. Effect of a High-Protein Diet versus Standard-Protein Diet on Weight Loss and Biomarkers of Metabolic Syndrome: A Randomized Clinical Trial. Obes Facts. 2017;10(3):238-251. doi:10.1159/000471485.
  • Carbone JW, Pasiakos SM. Dietary Protein and Muscle Mass: Translating Science to Application and Health Benefit. Nutrients. 2019;11(5):1136. Published 2019 May 22. doi:10.3390/nu11051136.


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