High-Protein Diets: What Research Shows for Weight, Muscle, Kidneys and Bones
What research found for higher-protein diets and weight, muscle, kidneys and bones, why healthy kidneys and kidney disease are different questions, and where evidence is missing.
Content last updated . This page has not been medically reviewed.
Kidney disease, liver disease, pregnancy or a child's diet? Talk to a clinician or registered dietitian before changing protein. See Protein and kidney disease and Protein and liver disease.
What counts as "high protein"?
There is no single definition. The kidney review below counted "higher protein" as at least 1.5 g per kg of body weight, or at least 20% of energy, or at least 100 g a day. [1] For comparison, Health Canada's Dietary Reference Intake table lists a Recommended Dietary Allowance (RDA) of 0.80 g per kg a day for men and women aged 19 and over, and the MedlinePlus encyclopedia gives 10% to 35% of calories as the range for healthy adults. [2][3] These are different units (g/kg, g/day and % of calories) and should not be swapped. See Protein units explained.Evidence labels used here: evidence in adequately nourished people, promising but limited, mixed, insufficient evidence, Proper evidence not found.
What research found
| Question | What the source found | Strength of evidence |
|---|---|---|
| Kidney function in healthy adults | A 2018 meta-analysis of randomized trials (28 analyzed, 1,358 participants, adults without kidney disease) found no difference in the change in filtering rate (GFR) between higher- and lower-protein diets. [1] The authors noted an unclear risk of selection bias in the included trials. [1] | Evidence in adequately nourished people; the review counted trials lasting more than 4 days, so long-term effects are not settled |
| Bone | A 2017 review for the National Osteoporosis Foundation (16 trials, 20 cohort studies) found moderate evidence that higher protein may help lumbar spine bone density, no effect at hip, femoral neck or total body, and no adverse effects of higher protein. [4] The authors said studies varied and confounding could not be excluded. [4] | Promising but limited |
| Weight loss | Trials that cut calories found modest advantages for a higher-protein diet; see Protein, fullness and weight management. [5] | Mixed over the long term: longer studies gave limited and conflicting findings [6] |
| Muscle with resistance training | Protein supplements added small gains in muscle size and strength; see Are protein supplements necessary?. [7] | Evidence in adequately nourished people |
Kidneys: healthy versus diseased
Healthy kidneys. The meta-analysis concluded that higher protein intakes did not adversely affect kidney function, measured as GFR, in healthy adults. [1]Chronic kidney disease. A 2017 review explains the concern: high protein intake may raise pressure inside the kidney's filters and cause hyperfiltration, which could damage filter structure or worsen CKD. [8] That review notes a low-protein diet of 0.6 to 0.8 g/kg a day is often recommended in CKD management, and that care should be individualized with dietitian counseling to avoid malnutrition. [8] The US National Institute of Diabetes and Digestive and Kidney Diseases says some people with CKD may need moderate protein so waste does not build up, but too little can cause malnutrition; people on dialysis may need more. [9] The right amount depends on the stage and treatment, so it is for a kidney team to set.
Older adults are a special case: the PROT-AGE position paper (2013) said people over 65 with severe kidney disease (GFR below 30) who are not on dialysis may need to limit protein. [10]
What the sources did not settle
- Kidney stones, heart disease, cancer and lifespan with long-term high protein: Proper evidence not found in this round. We searched PubMed for systematic reviews on protein and kidney stones and on high-protein diet risks and did not retrieve a usable review to read.
- People with kidney disease who do not know it: the kidney trials above included only adults without kidney disease, so they cannot tell us about people whose kidneys are already affected. If you are unsure about your kidney health, ask a clinician.
- Very high amounts for long periods: the reviews cover trial durations from days to months. We do not state a safe upper limit, and none is given in the sources we read.
- Protein source: the reviews above do not compare animal and plant sources for these outcomes in the abstracts we read.
Practical safety points
- Supplements: powders and bars add protein but also may add sweeteners, minerals or contaminants. See Protein powder safety and Quality testing and certifications.
- Medicines: if you take medicines for kidney, liver or diabetes conditions, ask a pharmacist before adding supplements. See How interactions work.
- Before surgery or in pregnancy: ask your care team first. See Supplements before surgery and Pregnancy and breastfeeding.
- Change a medicine? Never stop or change a prescribed medicine or diet plan without your clinician.
Related: Protein: what it does and where it comes from and Protein myths and misconceptions.
Frequently asked questions
Is a high-protein diet bad for healthy kidneys?
A 2018 meta-analysis of randomized trials in adults without kidney disease found higher-protein diets did not adversely change kidney filtering (GFR). The review counted trials of more than 4 days, so long-term effects are less certain. [1]
Is a high-protein diet safe with kidney disease?
Not assumed. Reviews describe low-protein approaches in CKD, and NIDDK says to work with a dietitian or health care professional on the right amount. People on dialysis may need different amounts. [8][9]
Does more protein harm bones?
A 2017 systematic review found no adverse effects of higher protein intake on bone and moderate evidence of a small benefit at the lumbar spine only. [4] See Protein and bone health.
How much protein is "too much"?
The sources we read do not give a universal upper limit. Official figures are for recommended intakes, such as 0.80 g/kg a day for adults 19 and over in Health Canada's table. A clinician or dietitian can look at your situation. [2]
Do protein shakes count as a high-protein diet?
Shakes are one way to add protein. Whether a total diet counts as "high" depends on all foods together; see Protein powders vs whole foods.
References
- Devries MC et al. Changes in kidney function do not differ between healthy adults consuming higher- compared with lower- or normal-protein diets: a systematic review and meta-analysis. J Nutr 2018. Read 2026-10-22.
- Health Canada, Dietary reference intakes tables: Reference values for macronutrients (2005 DRI values). Read 2026-10-22.
- MedlinePlus (US National Library of Medicine), Protein in diet. Read 2026-10-22.
- Shams-White MM et al. Dietary protein and bone health: a systematic review and meta-analysis from the National Osteoporosis Foundation. Am J Clin Nutr 2017. Read 2026-10-22.
- Wycherley TP et al. Effects of energy-restricted high-protein, low-fat compared with standard-protein, low-fat diets: a meta-analysis of randomized controlled trials. Am J Clin Nutr 2012. Read 2026-10-22.
- Leidy HJ et al. The role of protein in weight loss and maintenance. Am J Clin Nutr 2015. Read 2026-10-22.
- Morton RW et al. 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. Br J Sports Med 2018. Read 2026-10-22.
- Ko GJ et al. Dietary protein intake and chronic kidney disease. Curr Opin Clin Nutr Metab Care 2017. Read 2026-10-22.
- National Institute of Diabetes and Digestive and Kidney Diseases (NIH), Eating and nutrition for chronic kidney disease. Read 2026-10-22.
- Bauer J et al. Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE Study Group. J Am Med Dir Assoc 2013. Read 2026-10-22.