Recent Research Upends What We Know About Protein Intake

The recommended dietary protein intake for adults with minimal physical activity is 0.8 grams per kilogram (1.76 grams per pound) of body weight per day. Those with moderate activity levels are advised to consume 1.3 grams per kilogram (2.87 grams per pound). Individuals engaging in intense physical activity should aim for 1.6 grams per kilogram (3.53 grams per pound). (1)

Many experts agree that muscle growth is effectively supported within this range, with little evidence suggesting further benefits from exceeding it.

However, emerging research regarding protein intake for muscle growth suggests that natural bodybuilders preparing for competition may benefit from consuming as much as 1.3 grams of protein per pound (0.59 grams per kilogram) of lean body mass even though lower intakes are sufficient for most individuals to support muscle development effectively.

Dr. Mike Israetel and exercise scientist Dr. Milo Wolf delved deeper into the research and how adequate protein intake for muscle growth is defined.

[Related: Best Whey Isolate Protein Powders]

New Study

Dr. Wolf highlighted how many experts base their recommendations on the influential 2018 studies by Morton and colleagues. (2) These studies provided insights into the relationship between protein intake and lean body mass. Key findings include:

• Linear regression analysis demonstrated a clear correlation between protein consumption and lean body mass gains — the more protein consumed, the more significant the increase in lean body mass.
• Biphasic regression analysis offered a more accurate representation by accounting for diminishing returns — additional protein intake yields more minor benefits beyond a certain point.

These findings have become a cornerstone for understanding protein consumption and its impact on muscle growth. “That was the best piece of research we had for four years, but in 2022, Tagawa and colleagues performed another meta-analysis,” Wolf explained. The comprehensive analysis included more research and wasn’t limited to lifters. (3) 

The relationship between consistent protein intake and lifting performance was examined and accounted for various factors using three progressively refined models:

• Model One: No adjustments were made for confounding variables.
• Model Two: Adjustments were introduced for factors, including age, gender, and other demographic variables. The model acknowledged that protein sensitivity decreases with age.
• Model Three: Further adjustments factored in changes in body weight gained during the study period.

This layered approach provided a more nuanced understanding of protein’s role in lifting and physical performance across different contexts. The results of the comprehensive studies were:

1. When weight gain was not considered, lifters and non-lifters experienced more significant hypertrophy as their protein intake increased, up to a maximum of 1.3 grams per pound. “However, in non-lifters, once controlled for bodyweight gained, that relationship kind of went away, like past 0.7 grams per pound. If you’re no longer gaining weight, then it doesn’t matter,” Wolf noted.
2. Higher protein intake consistently promoted greater muscle growth among lifters, even after accounting for bodyweight gain. This effect was observed up to 1.3 grams of protein per pound of body weight, though diminishing returns became noticeable beyond 1.6 grams per kilogram. While the rate of improvement slowed at higher intakes, the overall trend remained positive.

Dr. Milo Wolf’s Recommendations

Dr. Wolf offers two insights from this paper:

1. For the average lifter who isn’t overly concerned with fine-tuning their protein intake, diminishing returns suggest a practical target of around 0.8 grams of protein per pound of body weight to support solid muscle growth.
2. For optimal muscle hypertrophy, a higher protein intake of 1 to 1.3 grams per pound of body weight is recommended. While Dr. Wolf notes that current data isn’t precise enough to pinpoint an exact number, staying within this range maximizes muscle development. 

Dr. Wolf explains that protein quality is rarely a concern unless someone follows a highly restrictive diet or relies solely on a single protein source. However, older adults and individuals on plant-based diets should increase their protein intake by around 20% to meet their nutritional requirements.

References

1. Wu G. (2016). Dietary protein intake and human health. Food & function, 7(3), 1251–1265. https://doi.org/10.1039/c5fo01530h 
2. Morton, R. W., Murphy, K. T., McKellar, S. R., Schoenfeld, B. J., Henselmans, M., Helms, E., Aragon, A. A., Devries, M. C., Banfield, L., Krieger, J. W., & Phillips, S. M. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British journal of sports medicine, 52(6), 376–384. https://doi.org/10.1136/bjsports-2017-097608 
3. Tagawa, R., Watanabe, D., Ito, K., Otsuyama, T., Nakayama, K., Sanbongi, C., & Miyachi, M. (2022). Synergistic Effect of Increased Total Protein Intake and Strength Training on Muscle Strength: A Dose-Response Meta-analysis of Randomized Controlled Trials. Sports medicine – open, 8(1), 110. https://doi.org/10.1186/s40798-022-00508-w

Featured image via Shutterstock/Elena Veselova

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