What research says about keeping muscle after 40, for lifters who want a simple plan without calorie counting.
You can keep your muscle after 40. The research points to two things you control: lifting and protein.
Lifting comes first
In a meta-analysis of 14 randomized trials of 561 older adults with sarcopenia (age-related muscle loss), resistance training improved handgrip strength, knee strength, and gait speed. It did not significantly change muscle mass in those trials. The authors note that gains in muscle size need longer programs, around 12 weeks or more, so give it time.
Key takeaway: Strength shows up first. Keep lifting for months, not weeks, before judging your muscle.
How much protein, and when
Protein helps most when you are already training. A meta-analysis of 49 trials found that protein supplementation improved strength and muscle size during resistance training, with no extra benefit beyond about 1.6 g per kg of body weight a day. The effect also shrank with age, so consistency matters.
Per meal, a 2024 review reports that adults over 60 need about 30 g of protein (roughly 2.8 g of leucine, an amino acid found in meat, dairy, and soy) in a meal to switch on muscle building. The same review says the response to a meal lasts only about 2 to 2.5 hours, which is why spreading protein across the day makes sense. It also admits the long-term payoff for muscle mass is still speculative. For more on amounts, see our piece on protein needs after 40.
What about the post-workout rush?
You may have heard you must eat within an hour of training. A meta-analysis on protein timing concluded that adequate total protein combined with resistance exercise is the key factor. Hit your daily number first and don’t sweat the clock around your workout.
Putting it together
- Lift two or three times a week and progress the weights.
- Build each meal around protein, aiming near 30 g.
- Keep meals regular so you don’t go long stretches without protein.
Proteinly can help with the habit part. It’s a protein-first app with no calorie counting, and its automatic eating timer reminds you to eat every 2 hours so regular protein becomes routine. The timer only reminds you to eat; it doesn’t build muscle itself.
Frequently asked questions
Do I need a leucine supplement?
The review above looks at leucine inside whole meals of about 30 g of protein. It doesn’t show that a separate supplement is needed, so start with food.
Is it too late to start at 50 or 60?
The sarcopenia trials above averaged ages from about 66 to 83, and resistance training improved strength in those groups.
Next steps
Pick a lifting schedule, build each meal around protein, and give it a few months. You can find more at Proteinly, and follow us on YouTube, TikTok and Instagram.