Muscle does not wait for retirement to start slipping. The National Institute on Aging (NIA) says muscle mass and strength “reach their peak at around 30 to 35 years of age.” After that, “muscle power and performance decline slowly and linearly at first, and then faster after age 65 for women and 70 for men” (NIA). That age-related loss is called sarcopenia, and NIA notes that “some forms of sarcopenia can also affect middle-aged people,” with poor nutrition and lack of exercise raising the odds.
Exercise and nutrition are the two factors NIA names there. This article covers the nutrition side for people training after 40, specifically protein: what the official minimum is, what the current Dietary Guidelines recommend, what resistance-training research found, and why age may change how you spread protein across the day.
Please read first: This article is general information, not medical or nutrition advice. It does not diagnose or treat any condition. If you have kidney disease, diabetes or another medical condition, or take medication, talk with your physician or a registered dietitian before changing how much protein you eat.
Key Takeaways
– The adult RDA for protein is 0.8 g per kilogram of body weight per day, a level set to prevent deficiency rather than to support optimal muscle.
– The 2025-2030 Dietary Guidelines for Americans set a goal of 1.2 to 1.6 g per kilogram per day.
– In a 2018 meta-analysis of resistance-training trials, protein beyond about 1.6 g per kilogram per day produced no further gains in lean mass.
– Older adults appear to need more protein per meal than younger adults, though most of that research studied people over 65.
What is the RDA for protein, and is it enough?
The Recommended Dietary Allowance (RDA) for adults is 0.8 grams of protein per kilogram of body weight per day, set by the National Academies’ Food and Nutrition Board (National Academies DRI tables, NCBI Bookshelf). For someone who weighs 80 kilograms (about 176 pounds), that works out to 64 grams a day.
The RDA is a floor, not a target. The scientific report behind the 2025-2030 Dietary Guidelines says the RDA “was established to prevent deficiency based on nitrogen-balance data,” and that it “does not reflect the intake required to maintain optimal muscle mass or metabolic function under all conditions” (Scientific Report, Dietary Guidelines 2025-2030).
For people who lift, a 2018 meta-analysis in the British Journal of Sports Medicine by Morton and colleagues put it plainly: “consuming protein at the RDA of 0.8 g protein/kg/day appears insufficient for those who have the goal of gaining greater strength and FFM with RET” (Morton et al., full text). FFM means fat-free mass, and RET means resistance exercise training.
How much protein do the current Dietary Guidelines recommend?
The Dietary Guidelines for Americans, 2025-2030, set protein serving goals of 1.2 to 1.6 grams per kilogram of body weight per day, “adjusting as needed based on your individual caloric requirements” (Dietary Guidelines for Americans). For the same 80-kilogram adult, that is roughly 96 to 128 grams a day.
The guidelines also tell Americans to “Prioritize Protein Foods at Every Meal,” and they note that “some older adults need fewer calories but still require equal or greater amounts of key nutrients such as protein.” That combination matters as you age. If you eat a little less overall, protein has to take up a bigger share of the plate to keep pace.
How much protein supports strength training?
Research on lifters lands in a similar range, with a ceiling. Morton’s 2018 meta-analysis pooled 49 randomized trials with 1,863 participants who did resistance training for at least six weeks. It found that “dietary protein supplementation significantly enhanced changes in muscle strength and size during prolonged RET in healthy adults” (PubMed).
The same analysis found a plateau: protein “beyond total protein intakes of 1.62 g/kg/day resulted in no further RET-induced gains in FFM.” Because the confidence interval around that figure ran from 1.03 to 2.20, the authors suggested “it may be prudent to recommend ~2.2 g protein/kg/d for those seeking to maximise resistance training-induced gains.” They also reported that “increasing age reduces and training experience increases the efficacy of protein supplementation.” In plain terms, added protein gave a smaller extra boost to older participants in those trials. That finding is about the size of the boost from supplements, not about how much protein older adults need overall.
| Source | Daily protein (g per kg of body weight) | Who it describes |
|---|---|---|
| RDA, National Academies | 0.8 | Adults, to prevent deficiency |
| PROT-AGE study group, 2013 | At least 1.0 to 1.2 | Adults over 65 |
| PROT-AGE study group, 2013 | 1.2 or more | Older adults who exercise or are otherwise active |
| Dietary Guidelines for Americans, 2025-2030 | 1.2 to 1.6 | Americans generally, adjusted for calorie needs |
| International Society of Sports Nutrition, 2017 | 1.4 to 2.0 | Most exercising individuals |
| Morton et al., 2018 | Plateau near 1.6, upper estimate about 2.2 | Adults doing resistance training |
The International Society of Sports Nutrition’s 2017 position stand says “an overall daily protein intake in the range of 1.4-2.0 g protein/kg body weight/day” is “sufficient for most exercising individuals” for building and maintaining muscle (PubMed).
Does age change how much protein you need per meal?
The research suggests it does, although most of it studied people well past 40. The PROT-AGE study group, an expert panel, wrote in 2013 that “older adults need more dietary protein than do younger adults.” For people over 65, it recommends “average daily intake at least in the range of 1.0 to 1.2 g protein per kilogram of body weight per day,” and “≥ 1.2 g/kg body weight/d” for “those who are exercising and otherwise active” (PubMed).
Per-meal amounts follow the same pattern. A 2015 analysis by Moore and colleagues pooled lab data on muscle protein synthesis (MPS), the building of new muscle protein, in healthy men. Measured per kilogram of lean body mass, MPS plateaued after a single dose of about 0.60 g in older men (around 71 years old), compared with about 0.25 g in younger men (around 22). The authors concluded that healthy older men “require a greater relative protein intake, in a single meal, than young men” (PubMed). The ISSN’s general guide is “0.25 g of a high-quality protein per kg of body weight, or an absolute dose of 20-40 g” per serving, and it says “higher doses (~40 g) are likely needed to maximize MPS responses in elderly individuals” (ISSN, full text).
Keep two things in mind. A 45-year-old sits between the young and old groups in these studies, so treat the older-adult figures as a direction of travel, not a number measured in your age group. The experts also disagree on timing. The ISSN suggests spreading protein “every 3-4 h, across the day,” while PROT-AGE says evidence on “timing of ingestion” is “not yet sufficient to support specific recommendations.”
Does protein matter if you are not lifting?
Protein works alongside training, not instead of it. The trials in Morton’s meta-analysis all paired protein with resistance training, and the federal Physical Activity Guidelines for Americans say adults “should also do muscle-strengthening activities of moderate or greater intensity and that involve all major muscle groups on 2 or more days a week” (HHS, Physical Activity Guidelines). For older adults, the guidelines add “multicomponent physical activity that includes balance training.”
NIA describes muscle-strengthening exercise as “key to maintaining existing strength, slowing the loss of muscle mass, and helping to prevent falls and fall-related injuries” (NIA, Three Types of Exercise). If you are getting started, our guides on strength training for women over 40 and strength training for men over 40 cover the training side.
Who should check with a doctor before eating more protein?
Anyone with kidney disease, at minimum. PROT-AGE makes an exception for “older people with severe kidney disease” who “are not on dialysis,” saying “these individuals may need to limit protein intake.” The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) says some people with chronic kidney disease “may need to consume moderate amounts of protein,” that “too little protein may lead to malnutrition,” and that they should “work with a dietitian or health care professional to find the right balance” (NIDDK).
The same goes for anyone managing another medical condition. A registered dietitian can set a target that fits your health, your training and your appetite. For how functional nutrition approaches this, see our article on functional nutrition in Santa Monica.
Frequently Asked Questions
How much protein should I eat a day after 40?
The adult RDA is 0.8 g per kilogram of body weight, but that is a minimum set to prevent deficiency. The 2025-2030 Dietary Guidelines set a goal of 1.2 to 1.6 g per kilogram per day, adjusted for your calorie needs. A dietitian can tailor that to your health and your training.
Is the RDA enough if I lift weights?
Probably not, if your goal is to gain strength and muscle. A 2018 meta-analysis of resistance-training trials said protein at the 0.8 g per kilogram RDA “appears insufficient” for that goal. In the same analysis, gains in lean mass leveled off at total intakes above about 1.6 g per kilogram per day.
How much protein should be in each meal?
The International Society of Sports Nutrition suggests about 0.25 g per kilogram of body weight, or 20 to 40 g, per serving. It says around 40 g is likely needed for elderly people, a figure from research on adults well past 40. A lab analysis found older men needed more per meal than younger men. Experts still disagree on exact timing across the day.
Do I need protein supplements?
Not necessarily. The plateau in the 2018 meta-analysis was for total daily protein from all sources, and the 2025-2030 Dietary Guidelines focus on prioritizing protein foods at every meal. If food alone falls short of your target, ask a dietitian whether a supplement makes sense for you.
Strength training and nutrition in Santa Monica
If you are in Santa Monica and want to talk about strength training and nutrition after 40, you can reach Integrative Training Institute at 310.570.6352 or through the contact page. The studio is at 1358 Michigan Ave, Santa Monica, CA 90404. You can also read the personal training and nutrition pages.
Sources
- National Academies, Food and Nutrition Board, Dietary Reference Intakes tables (protein RDA), NCBI Bookshelf, retrieved 2026-10-08, https://www.ncbi.nlm.nih.gov/books/NBK545442/table/appJ_tab4/
- US Department of Health and Human Services and US Department of Agriculture, Dietary Guidelines for Americans, 2025-2030, retrieved 2026-10-08, https://cdn.realfood.gov/DGA.pdf
- Scientific Report for the Dietary Guidelines for Americans, 2025-2030, retrieved 2026-10-08, https://cdn.realfood.gov/Scientific%20Report_508.pdf
- Morton 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, British Journal of Sports Medicine, 2018, retrieved 2026-10-08, https://pubmed.ncbi.nlm.nih.gov/28698222/
- Bauer et al., Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE Study Group, Journal of the American Medical Directors Association, 2013, retrieved 2026-10-08, https://pubmed.ncbi.nlm.nih.gov/23867520/
- Jäger et al., International Society of Sports Nutrition Position Stand: protein and exercise, Journal of the International Society of Sports Nutrition, 2017, retrieved 2026-10-08, https://pubmed.ncbi.nlm.nih.gov/28642676/
- Moore et al., Protein ingestion to stimulate myofibrillar protein synthesis requires greater relative protein intakes in healthy older versus younger men, Journals of Gerontology: Series A, 2015, retrieved 2026-10-08, https://pubmed.ncbi.nlm.nih.gov/25056502/
- US Department of Health and Human Services, Physical Activity Guidelines for Americans, 2nd edition, retrieved 2026-10-08, https://odphp.health.gov/sites/default/files/2019-09/Physical_Activity_Guidelines_2nd_edition.pdf
- National Institute on Aging, How can strength training build healthier bodies as we age?, retrieved 2026-10-08, https://www.nia.nih.gov/news/how-can-strength-training-build-healthier-bodies-we-age
- National Institute on Aging, Three Types of Exercise Can Improve Your Health and Physical Ability, retrieved 2026-10-08, https://www.nia.nih.gov/health/exercise-and-physical-activity/three-types-exercise-can-improve-your-health-and-physical
- NIH National Institute of Diabetes and Digestive and Kidney Diseases, Healthy Eating for Adults with Chronic Kidney Disease, retrieved 2026-10-08, https://www.niddk.nih.gov/health-information/kidney-disease/chronic-kidney-disease-ckd/healthy-eating-adults-chronic-kidney-disease