Protein is the key to muscle gain, but what happens if you consume too much? Will you gain extra muscle or excess fat? In a March 2025 podcast, nutrition expert Thomas DeLauer and nutritional scientist Dr. Layne Norton dissected the facts of protein overconsumption.
You can gain body fat from [protein], but it’s hard to gain fat from overeating protein. It’s a long journey from protein to amino acids, to glucose or ketones, then fatty acids.
—Dr. Layne Norton
Protein undergoes a complex metabolic process that makes it less likely to be converted into body fat. (1) Studies show that carbohydrates also result in minimal fat gain, though it depends on their glycemic index. In contrast, dietary fats are the most likely to be stored as body fat. (2)(3)
[Related: Be Aware of These 5 Protein Myths]
Muscle vs. Fat
Can protein overfeeding result in more muscle gains? The short answer is yes. Study subjects who over-consume protein gained lean mass, though protein can still contribute to fat gain in a caloric surplus.
However, there may be an upper protein limit. Beyond a certain amount — 2.2 grams per kilogram of body weight — the benefits may plateau for most. (4)
Protein’s Thermic Effect, Satiety, and Supplements
Dr. Norton delved into why protein behaves differently metabolically, highlighting its thermic effect (TEF).
Protein has the highest thermic effect — about 20 to 30 percent of its calories are burned during digestion.
—Dr. Layne Norton
Out of 100 protein calories, 20 to 30 are expended via metabolism; carbs have a TEF of five to 10 percent, and fats only roughly 0-to-3%. This effect helps prevent fat gain and promote weight loss.
Protein generally seems more satiating than carbs and fats, which reduces caloric intake and supports fat loss efforts and health factors. (5)
According to Dr. Norton, excess protein is not stored as fat if you max out protein synthesis.
Whatever is leftover is oxidized and converted to glucogenic substrates.
—Dr. Layne Norton
Dr. Norton doesn’t see the benefit of branched-chain amino acids (BCAAs) or collagen protein supplements. Data shows they offer minimal benefits for muscle growth. (6)(7) He asserted that a high-protein diet and protein supplements are adequate.
High Protein and Kidneys
While high-protein diets appear beneficial, there are common concerns about kidney safety. Research suggests that while the kidneys can adapt to higher protein intakes, consuming too much protein may exacerbate pre-existing kidney issues. Qualified health professionals should carefully monitor chronic health conditions.
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References
- Bray GA, Smith SR, de Jonge L, Xie H, Rood J, Martin CK, Most M, Brock C, Mancuso S, Redman LM. Effect of dietary protein content on weight gain, energy expenditure, and body composition during overeating: a randomized controlled trial. JAMA. 2012 Jan 4;307(1):47-55. doi: 10.1001/jama.2011.1918. Erratum in: JAMA. 2012 Mar 14;307(10):1028. PMID: 22215165; PMCID: PMC3777747.
- Bosy-Westphal A, Müller MJ. Impact of carbohydrates on weight regain. Curr Opin Clin Nutr Metab Care. 2015 Jul;18(4):389-94. doi: 10.1097/MCO.0000000000000193. PMID: 26049636.
- Bennett C, Reed GW, Peters JC, Abumrad NN, Sun M, Hill JO. Short-term effects of dietary-fat ingestion on energy expenditure and nutrient balance. Am J Clin Nutr. 1992 Jun;55(6):1071-7. doi: 10.1093/ajcn/55.6.1071. PMID: 1595577.
- Antonio J. High-protein diets in trained individuals. Res Sports Med. 2019 Apr-Jun;27(2):195-203. doi: 10.1080/15438627.2018.1523167. Epub 2018 Sep 22. PMID: 30244609.
- Leidy HJ, Clifton PM, Astrup A, Wycherley TP, Westerterp-Plantenga MS, Luscombe-Marsh ND, Woods SC, Mattes RD. The role of protein in weight loss and maintenance. Am J Clin Nutr. 2015 Jun;101(6):1320S-1329S. doi: 10.3945/ajcn.114.084038. Epub 2015 Apr 29. PMID: 25926512.
- Martinho DV, Nobari H, Faria A, Field A, Duarte D, Sarmento H. Oral Branched-Chain Amino Acids Supplementation in Athletes: A Systematic Review. Nutrients. 2022 Sep 27;14(19):4002. doi: 10.3390/nu14194002. PMID: 36235655; PMCID: PMC9571679.
- Khatri M, Naughton RJ, Clifford T, Harper LD, Corr L. The effects of collagen peptide supplementation on body composition, collagen synthesis, and recovery from joint injury and exercise: a systematic review. Amino Acids. 2021 Oct;53(10):1493-1506. doi: 10.1007/s00726-021-03072-x. Epub 2021 Sep 7. PMID: 34491424; PMCID: PMC8521576.
Featured image via Shutterstock/Mironov Vladimir
