How Much Protein You Need After 40 to Keep Muscle

By Longevity Lab · Published: July 21, 2026

Based on peer-reviewed research — full source list at the end of this article. This is educational information, not medical advice.

After 40, the working target is about 1.2–1.6 g of protein per kg of body weight a day — roughly 85–110 g for a person weighing 70 kg (154 lb) — to hold on to muscle as you age. That is well above the classic 0.8 g/kg figure, because aging muscle responds less strongly to the same amount of protein. Around this topic there is a lot of noise: that too much protein wrecks your kidneys, or that a normal diet already covers it. Here is what the data says about how much protein you actually need with age, why it matters for Longevity, how to spread it through the day, and where to get it.

Why you need more protein as you age

Over the years a phenomenon called anabolic resistance sets in: aging muscle responds less strongly to protein and to training, and needs a bigger signal to switch on muscle protein synthesis. At the same time, muscle loss speeds up — sarcopenia, which leads to weakness, a higher risk of falls, and loss of independence (more on this in strength training against sarcopenia). So the conclusion is counterintuitive but consistent: older adults need no less protein than younger adults, and probably more. Because sarcopenia creeps up quietly, it helps to track a number rather than a feeling, and a Body composition assessment gives you the muscle-mass indices you can re-check every few months.

How much protein you need

The classic 0.8 g/kg figure was set to prevent deficiency in young adults, not to preserve muscle with age. Current recommendations for people over 40–50 are higher:

For a person weighing 70 kg (154 lb) that works out to roughly 85–110 g of protein a day. If you are not sure which weight to base the calculation on, a Metabolic age by lifestyle and body composition estimate gives you body-fat percentage, muscle mass and an ideal-weight range to work from. One important caveat: in CKD (chronic kidney disease) the target is set by a doctor, and the approach there is different.

Distribution matters more than you think

Muscle protein synthesis switches on at a threshold: a single meal needs roughly 25–30 g of quality protein (with enough of the amino acid leucine, one of the essential Amino acids) to give muscle a full signal. That is why it is better to spread protein across all your meals instead of eating almost all of it at dinner. Breakfast is where most people fall short, so adding protein there — eggs, cottage cheese, yogurt — is a simple and effective step.

Protein sources

Both animal and plant sources are useful:

• animal — fish, eggs, poultry, dairy: a complete amino acid profile and good digestibility;
• plant — legumes, soy, tofu: an excellent complement to the diet that also brings fiber; combine them to cover the full set of amino acids;
• fish also supplies omega-3, which makes it especially valuable.

The best pattern for longevity is a plant-forward diet (along Mediterranean lines) with enough protein, but not an excess of it.

Protein and the kidneys: clearing up the myth

A common fear is that a lot of protein damages the kidneys. In healthy people this is not supported: studies find no harm to normally functioning kidneys from a higher protein intake. Caution really is needed only when chronic kidney disease is already present, and there the diet is set by a doctor. For a healthy person, adequate protein is a benefit, not a risk. If you want to confirm that your kidneys belong in that healthy group before you raise your intake, a creatinine test plus a Glomerular filtration rate (eGFR) calculation will show where your filtration stands.

Frequently asked questions

Sources

Disclaimer. This article is for information only and does not replace medical advice. Talk to a qualified clinician before changing anything about your health.