1.6 grams of protein per kilo is a well-supported target for building muscle, even after 55

Evidence check, September 27, 2026

The claim: "To build muscle, and to keep it while you lose weight, eat about 1.6 grams of protein per kilo of your target body weight."

Our grade: Solid. In dozens of randomized trials, extra protein added to the muscle people built by lifting, with little further gain past about 1.6 g/kg a day, and higher protein helped people keep muscle while losing weight. Lifting does most of the work; protein adds a smaller, real boost.

You're 60. You've started lifting twice a week, and you want the muscle to show up. Someone on a podcast says to eat a gram of protein per pound. Someone else says 1.6 grams per kilo. A friend says you'll never build muscle without meat.

How much protein do you actually need, and does it have to come from animals?

It matters because muscle is what keeps you strong, steady on your feet and able to carry your own groceries at 85. A new trial in adults 55 and older, published this week, tested exactly this, and it sits on top of more than 70 earlier trials.

Where the claim came from

The 1.6 number comes from a 2018 analysis of 49 randomized trials by Stuart Phillips's lab at McMaster University [4]. It has since become a standard line on longevity podcasts.

On Gabrielle Lyon's show in 2024, Ted Naiman put it this way: you don't need "more than 1.6 grams per kg of ideal body weight" for maximum muscle building, and Lyon agreed the evidence "is really 1.6 grams per kg" [1]. Both like to aim a little higher, at 1 gram per pound (2.2 g/kg), for fullness. Lyon's own plan bases protein on your target weight if you have weight to lose [2]. Peter Attia tells his patients 2 g/kg [3].

Lyon also said the less protein you eat, the more it matters that it comes from animal foods [1]. The new trial tested that too.

Clue one: extra protein adds muscle, up to a point

The Phillips analysis pooled 49 randomized trials with 1,863 people who lifted weights for at least 6 weeks, some with extra protein and some without [4]. The extra protein added about 0.3 kg of lean mass and 2.5 kg to their best lift, on top of what lifting alone gave.

The gains flattened out at about 1.62 grams per kilo per day. Past that, more protein added nothing measurable. The estimate is fuzzy: the true level could be anywhere from about 1.0 to 2.2. That's why the authors say 2.2 is the safe choice for people who want every last bit of muscle [4].

A bigger 2022 analysis, 74 randomized trials in healthy adults, found the same pattern [5]. For people under 65, the extra muscle showed up at 1.6 g/kg or more. For people 65 and older, it showed up at 1.2 to 1.59.

Clue two: lifting works after 55, with or without meat

The new IMPACT trial, from the Netherlands, randomly split 108 adults aged 55 and older (average 66, 58% women) into two diets for 12 weeks [6]. Everyone lifted weights 3 times a week. Both groups were told to eat at least 1.2 g/kg of protein. One group got most of it from plants, eggs and dairy (a vegetarian diet). The other got most of it from animal foods, meat included.

Both groups gained muscle in their arms and legs, measured by body scan: 0.38 kg for the vegetarians and 0.66 kg for the meat eaters. Both got stronger on the leg press and faster at standing up from a chair, and here the two groups came out the same.

The vegetarians also ate less protein: 1.24 g/kg against 1.58 g/kg for the meat eaters. So the trial can't say whether the meat eaters' extra muscle came from the meat or from the extra protein. It fits both Lyon's point and the 1.6 target.

Clue three: protein protects muscle while you lose weight

When you eat less to lose weight, part of what you lose is muscle. A 2012 analysis of 24 randomized trials with 1,063 adults compared diets with the same calories but more or less protein, for about 12 weeks on average [7]. The higher-protein diets kept 0.43 kg more lean mass and took off 0.87 kg more fat.

A small, tough trial in 40 young men shows how far this can go [8]. For 4 weeks they ate 40% fewer calories than they needed and trained 6 days a week. The men eating 2.4 g/kg of protein gained 1.2 kg of lean mass and lost 4.8 kg of fat. The men eating 1.2 g/kg gained 0.1 kg of lean mass and lost 3.5 kg of fat.

So back to you at 60, lifting twice a week. The lifting is what builds the muscle, at any age. Protein near 1.6 g/kg gives it the most to work with, and meat isn't required if you hit your number.

Our grade

The case for the other side: the extra muscle from protein is small, about a third of a kilo over several months. The 1.6 cutoff isn't sharp; some people, especially older ones, may do better a bit higher, which is why Attia and Lyon aim for 2 to 2.2. Many of the trials were small and short, and some of the researchers have had funding from dairy and meat groups [4, 5]. And using your target weight makes sense so a heavier person doesn't overshoot, but no trial has compared it with current weight.

What would change the grade: a large trial that tests set protein levels head to head in adults over 60, for a year or longer.

What this means for you

• Lift weights 2 to 3 times a week. That's the main thing. In IMPACT, both groups got stronger in 12 weeks.
• Aim for about 1.6 g of protein per kilo of target weight a day. That's about 0.7 g per pound. For a target of 68 kg (150 lb), that's about 110 g a day.
• If you're over 65, don't settle for less than 1.2 g/kg. More is fine if you like it.
• If you're losing weight, keep protein high and keep lifting. That's how you lose fat instead of muscle.
• If you're vegetarian, make sure you actually reach your number. Eggs, dairy, soy, lentils and a protein powder help.

What's next

This is the first article in our new Strength and muscle series. Next: how much protein you really need after 50, and creatine for older adults. If you're on a GLP-1 drug, our check of how much muscle Ozempic costs covers protecting muscle while losing weight fast.

Sources

1. Lyon G, Naiman T. Achieve your ideal body composition. The Dr. Gabrielle Lyon Show, March 6, 2024. Podcast transcript. https://drgabriellelyon.com/podcast_list/achieve-your-ideal-body-composition-dr-ted-naiman
2. Lyon G. The Lyon Protocol. drgabriellelyon.com, 2024. Guide (PDF). https://drgabriellelyon.com/wp-content/uploads/2024/01/The-Lyon-Protocol-Dr.-Gabrielle-Lyon.pdf
3. Attia P. Protein. peterattiamd.com, accessed September 27, 2026. https://peterattiamd.com/category/protein
4. Morton RW, Murphy KT, McKellar SR, 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. 49 randomized trials, 1,863 participants, 6+ weeks of training. One author has had funding from the US National Dairy Council. https://doi.org/10.1136/bjsports-2017-097608
5. Nunes EA, Colenso-Semple L, McKellar SR, et al. Systematic review and meta-analysis of protein intake to support muscle mass and function in healthy adults. J Cachexia Sarcopenia Muscle, 2022. 74 randomized trials. Some authors have had funding from dairy and beef groups or work for nutrition companies. https://doi.org/10.1002/jcsm.12922
6. van Oppenraaij SL, Weijs PJM, Verlaan S. Effects of a self-selected vegetarian vs. omnivorous diet on protein intake and muscle mass in older adults during resistance exercise: the IMPACT randomized controlled trial. Am J Clin Nutr, 2026. 108 adults aged 55+, randomized, 12 weeks. https://doi.org/10.1016/j.ajcnut.2026.101533
7. Wycherley TP, Moran LJ, Clifton PM, 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. 24 randomized trials, 1,063 participants, about 12 weeks. https://doi.org/10.3945/ajcn.112.044321
8. Longland TM, Oikawa SY, Mitchell CJ, et al. Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss: a randomized trial. Am J Clin Nutr, 2016. 40 young men, randomized, 4 weeks. https://doi.org/10.3945/ajcn.115.119339