High-protein diets have been a staple in the world of bodybuilding and fitness for years now. Lately, they have gotten a lot of attention from the general public, and not all of it is good.
Many claim that high protein is over hyped, bad for your kidneys, and a waste (because you apparently can't absorb it all).
This article is going to look into high-protein diets and see how much you should really be eating, and if you're just wasting money.
Key Points To Know!
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What Is A High-Protein Diet?
Let's first discuss what a high-protein diet is, as everyone has their own idea. While there is no official definition or threshold, we think these 3 groupings work.
- Minimum health requirement (RDA): 0.8 g/kg/day
- Moderate / fitness-oriented intake: 1.2–1.6 g/kg/day
- High-protein range: 1.6–2.2+ g/kg/day
For this article, we'll mainly be talking about the moderate-high protein range in addition to the general idea of increasing protein.
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How Much Protein Can You Eat?
- Studies show your body absorbs nearly all the protein you eat.
- The maximum amount of protein utilized for muscle growth during the day is 1.6-2.2g/kg (Schoenfeld et al., 2019).
- The maximum amount of protein utilized for muscle growth in one meal is 0.4-0.6 g/kg (0.18-0.27 g/lb) (Helms et al., 2014).
A common claim is that your body can only absorb so much protein and just expels the excess. The reality is that this grossly underestimates how complex your body is.
Once protein is digested, amino acids are absorbed into the bloodstream and transported for multiple functions. The big one is muscle protein synthesis (MPS), which builds muscle.
But that's not the only function amino acids are needed for. This includes things like;
- Building hair, skin, and nails
- Forming enzymes and hormones
- Supporting your immune system
- It can be used as energy (under extreme circumstances)
Research shows your body absorbs nearly all the protein you eat (Antonio et al., 2024). The real question is how much is directed toward muscle protein synthesis and how much is sent elsewhere.
How Much Protein Can You Eat In One Day?
Protein utilization for muscle seems to max out at around 1.6-2.2g/kg (Schoenfeld et al., 2019). This should then be spread out throughout the day in 4-6 servings of relatively even amounts with;
- No serving should be less than 20g
- Your largest serving should be taken after your workout.
How Much Protein Can You Absorb In One Meal?
Most studies show the threshold is around 0.4-0.6 g/kg (0.18-0.27 g/lb) in one sitting. For a 180 lbs person, this would be 30-50 grams.
However, this number could be even higher depending on several factors (Schoenfeld et al., 2019). This includes;
- Eating a slow-release protein like casein (Schoenfeld & Aragon, 2018)
- Eating protein as part of a larger meal
- Consuming protein after a workout when MPS is elevated.
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Are High-Protein Diets Bad For Your Kidneys?
- Amino acids (protein) must pass through your kidneys because they contain nitrogen.
- Increased filtering is a normal process.
- In healthy individuals, there does not seem to be a limit to protein intake.
- Concern about protein and kidney health is aimed at clinical populations who already have damaged kidneys.
One of the most persistent protein fears: "Too much protein will damage your kidneys."
As with most myths, there's a grain of truth in certain scenarios that have been exaggerated and applied to the entire population.
Here's what actually happens.
Unlike carbohydrates and fats, amino acids contain nitrogen. This is why protein must be metabolized by your kidneys, and they don't.
During its metabolization, this nitrogen must be processed and excreted. More protein means greater filtration is required, leading to a condition called glomerular hyperfiltration.
In the past, some researchers thought this increased workload could eventually result in kidney damage. However, changes in kidney workload are not the same thing as kidney damage (Jäger et al., 2017)
For healthy people, this increased filtration is a normal adaptive response, similar to how your heart beats faster during exercise.
Who Shouldn't Eat High-Protein Diets?
Clinical populations, particularly people who already have chronic kidney disease (CKD). In those cases, dietary protein may need to be moderated to reduce stress on already compromised kidneys (Jäger et al., 2017)
But even here it isn't straightforward.
Research suggests that long-term heavy intake of red meat may increase the risk of CKD, while dairy, poultry, and plant proteins appear neutral or even protective (Knight et al., 2003).
So the concern isn't "protein," but context, health status, and protein source.
How Much Protein Intake Is Safe For Kidneys?
In healthy individuals, there doesn't seem to be a limit.
Evidence shows that higher protein intake in healthy individuals and athletes does not harm the kidneys.
- Athletes regularly consuming 2g/kg/day show normal kidney markers.
- Longitudinal studies of resistance training and protein supplementation report no renal impairment.
- Controlled trials testing with very high intakes of 3–4+ g/kg/day show stable kidney function markers.
Does Consuming "Excess" Protein Increase Body Fat?
- Eating excess protein does not automatically turn into fat; eating too many calories does
- High-protein diets have consistently been found to be effective weight-loss strategies.
- Very high-protein diets (3-4g/kg) have been shown to be effective for body recomposition (increasing muscle while losing fat) in trained athletes.
It can if you eat too many calories, but this is true for fat and carbs, too.
But the idea that "excess" protein not used for MPS automatically turns to fat is simply false.
Weight Gain Is Caused By Excess Calories, Not Specific Macros
In the simplest terms, your weight will go up if you eat too much of any macronutrient or composition. So if your "excess" protein intake is causing a caloric surplus, it could make you gain fat.
The irony is that, among fat, carbs, and protein, protein is least likely to cause fat gain.
In fact, it can help improve your body composition. Research has shown that when similar calories are eaten, diets with higher protein content result in;
- Increased lean mass gain
- Mitigation of muscle loss.
- Greater fat loss
Researchers have concluded that excess calories cause fat gain, while protein primarily influences muscle and metabolic rate.
High-Protein Diets Can Improve Body Composition
High protein diets have been found to be a very effective diet strategy as they lead to;
- Preserves lean mass during fat loss
- Promotes greater fat loss
- Improves satiety and dietary adherence
This holds true across trained individuals, sedentary adults, and overweight populations.
At the same time, people on higher-protein diets also tend to naturally reduce their intake of refined carbohydrates and sugary foods (Antonio et al., 2024).
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Very High Protein Diets Are Used In Body Recomposition
There have been several studies that have used protein intakes that even "high-protein" advocates would second-guess. We're talking about 3-4g/kg (Antonio et al., 2014).
Most of these studies have been used to research body recomposition in resistance-trained individuals. These studies have found;
- Extremely high protein intake paired with increased calories did not automatically increase fat mass.
- Lean mass gains were maintained or improved.
- Body fat would either decrease or remain the same
- Increase muscle mass while decreasing fat loss.
In some cases, higher protein intake was associated with greater fat loss, even when total calorie intake increased.
And this occurred in trained athletes who already had a healthy weight, i.e., not a beginner effect.
Can a High-Protein Diet Harm Bone Health?
Does eating a lot of protein "leach calcium from your bones?" That sounds scary.
However, when we look at the evidence, it's another case of concern being blown out of proportion.
Why Do People Say Protein Is Bad For Your Bones?
The concern comes from the acid-ash hypothesis that suggests diets high in acid-forming foods, including protein, can disrupt the body's acid-base balance.
Over time, this imbalance may lead to various health issues, including osteoporosis, as calcium is released from bones to neutralize acidity (Fenton et al., 2009).
It is true that higher protein intake can increase calcium excretion in urine. However, urinary calcium does not automatically equal bone loss.
Later research has shown that higher protein intake also increases intestinal calcium absorption, leading to greater calcium retention rather than loss. When total calcium balance and bone markers are observed, the "calcium drain" largely disappears (Fenton et al., 2009)
It's important to note that low fruit and vegetable intake as a result of high-protein diets may be a greater concern for acid load and bone health concerns.
Protein Actually Helps Build Your Bones
Bone isn't just mineral but a living tissue built on a protein matrix. Roughly one-third of bone mass is protein, making adequate protein intake essential for maintaining its structure.
Protein also supports bone indirectly by:
- Stimulating insulin-like growth factor-1 (IGF-1), which promotes bone formation
- Supporting muscle mass and strength, which increase mechanical loading on bone
- Improving physical function for long-term skeletal health
Protein and resistance training are the single best ways to encourage bone growth.
High Protein Has Not Shown To Decrease Bone Mineral Density
When researchers examine bone mineral density, fracture risk, and long-term skeletal health, any fear disappears.
Meta-analyses and consensus papers report that:
- Protein intake within and above recommended athletic ranges does not harm bone health.
- Higher protein intake is often associated with greater bone mineral density.
- Adequate protein combined with sufficient calcium intake may reduce bone loss in older adults (Rizzoli et al., 2018).
Even long-term studies in exercising populations consuming higher protein intakes show no negative impact on bone density compared to moderate intake (Antonio et al., 2024).
The consensus is that protein is either neutral or beneficial for bone health, especially when dietary quality is adequate.
Final Say On High Protein Intake And Health
Much of the fear of high protein occurs from the same basic mistakes: ignoring the complexity of the human body, inappropriately applying research to the whole population, and conflating terms.
In reality, high-protein diets tend to actually benefit your health and body composition, not harm it. At the same time, it's important to remember it's not the only nutrient you need.
Eating plenty of fruits, vegetables, and healthy fats is essential for optimal health. Add resistance training and physical activity on top, and you'll surely optimize your health and quality of life.
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FAQ: High Protein Intake
1. Is there a limit to how much protein your body can absorb in one sitting?
Your body absorbs nearly all the protein you eat; there's no set limit per meal. Muscle building benefits may plateau, but extra protein is used for other bodily functions.
2. Does eating more protein than you need automatically turn into body fat?
Eating excess protein doesn't automatically turn into fat. Only a calorie surplus causes fat gain, and protein is the least likely macronutrient to do this.
3. Is a high-protein diet bad for your kidneys?
High-protein diets are safe for healthy kidneys. Only those with existing kidney disease need to limit their protein intake.
4. Can eating a lot of protein weaken your bones?
Protein does not weaken bones; it actually supports bone strength. Studies show that higher protein intake is either neutral or beneficial for bones when calcium is sufficient.
5. How much protein can your body actually use for muscle growth per meal?
Muscle growth per meal plateaus at around 0.4g/kg-0.6g/kg, but the body still uses extra protein.
6. Is eating a high-protein diet safe long-term?
High-protein diets are safe in the long term for healthy people. Long-term studies show no harm to the kidneys, liver, bones, or heart.
7. Do high-protein diets help with fat loss?
High-protein diets help with fat loss by preserving muscle and increasing fullness. They lead to more fat loss and less muscle loss.
8. Can you eat too much protein?
You can't eat "too much" protein unless it's far beyond your needs, which offers no extra benefit. Excess protein isn't dangerous for healthy people, but may be impractical.
9. Does timing protein intake matter?
Timing can help, but total protein intake is most important and the first priority.
Spreading protein across meals supports steady amino acid availability and muscle repair, especially around training. However, total daily intake is the primary driver of results.
References
- Antonio J, Peacock CA, Ellerbroek A, Fromhoff B, Silver T. The effects of consuming a high protein diet (4.4 g/kg/d) on body composition in resistance-trained individuals. J Int Soc Sports Nutr. 2014 May 12;11:19. doi: 10.1186/1550-2783-11-19. PMID: 24834017; PMCID: PMC4022420. https://pubmed.ncbi.nlm.nih.gov/24834017/
- Antonio, J., Ellerbroek, A., Silver, T., Orris, S., Scheiner, M., Gonzalez, A., & Peacock, C. A. (2016). A high protein diet has no harmful effects: A one-year crossover study in resistance-trained males. Journal of Nutrition and Metabolism, 2016, 9104792. https://doi.org/10.1155/2016/9104792
- Antonio, J., Evans, C., Ferrando, A. A., Stout, J. R., Antonio, B., Cinteo, H., Harty, P., Arent, S. M., Candow, D. G., Forbes, S. C., Kerksick, C. M., Pereira, F., Gonzalez, D., & Kreider, R. B. (2024). Common questions and misconceptions about protein supplementation: what does the scientific evidence really show?. Journal of the International Society of Sports Nutrition, 21(1), 2341903. https://doi.org/10.1080/15502783.2024.2341903
- Fenton, T. R., Lyon, A. W., Eliasziw, M., Tough, S. C., & Hanley, D. A. (2009). Meta-analysis of the effect of the acid-ash hypothesis of osteoporosis on calcium balance. Journal of Bone and Mineral Research, 24(11), 1835–1840. https://doi.org/10.1359/jbmr.090515
- Helms, E. R., Aragon, A. A., & Fitschen, P. J. (2014). Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. Journal of the International Society of Sports Nutrition, 11(1), Article 20. https://doi.org/10.1186/1550-2783-11-20
- HHS & USDA. (2025). Dietary Guidelines for Americans, 2025–2030. U.S. Government.
- National Institutes of Health Office of Dietary Supplements. (2024). Nutrient recommendations: Recommended Dietary Allowances (RDAs). U.S. Department of Health and Human Services.
- Jäger, R., Kerksick, C. M., Campbell, B. I., Cribb, P. J., Wells, S. D., Skwiat, T. M., Purpura, M., Ziegenfuss, T. N., Ferrando, A. A., Arent, S. M., Smith-Ryan, A. E., Stout, J. R., Arciero, P. J., Ormsbee, M. J., Taylor, L. W., Wilborn, C. D., Kalman, D. S., Kreider, R. B., Willoughby, D. S., Hoffman, J. R., & Antonio, J. (2017). International Society of Sports Nutrition Position Stand: Protein and exercise. Journal of the International Society of Sports Nutrition, 14, 20. https://doi.org/10.1186/s12970-017-0177-8
- Kerstetter, J. E., O'Brien, K. O., & Insogna, K. L. (2003). Dietary protein, calcium metabolism, and skeletal homeostasis revisited. The American Journal of Clinical Nutrition, 78(3 Suppl), 584S–592S. https://doi.org/10.1093/ajcn/78.3.584S
- Knight, E. L., Stampfer, M. J., Hankinson, S. E., Spiegelman, D., & Curhan, G. C. (2003). The impact of protein intake on renal function decline in women with normal renal function or mild renal insufficiency. Annals of Internal Medicine, 138(6), 460–467 https://doi.org/10.7326/0003-4819-138-6-200303180-00009
- National Institutes of Health, Office of Dietary Supplements. (n.d.). Dietary reference intakes (DRIs): Recommended dietary allowances and adequate intakes. U.S. Department of Health and Human Services. https://ods.od.nih.gov/HealthInformation/Dietary_Reference_Intakes.aspx
- Rizzoli, R., Biver, E., Bonjour, J.-P., Coxam, V., Goltzman, D., Kanis, J. A., Lappe, J., Rejnmark, L., Sahni, S., & Weaver, C. (2018). Benefits and safety of dietary protein for bone health—An expert consensus paper endorsed by the European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases and by the International Osteoporosis Foundation. Osteoporosis International, 29(9), 1933–1948. https://doi.org/10.1007/s00198-018-4534-5
- Schoenfeld, B. J., & Aragon, A. A. (2018). How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution. Journal of the International Society of Sports Nutrition, 15(1), Article 10. https://doi.org/10.1186/s12970-018-0215-1
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