07/03/2026
Why Do You Need More Protein After 40?
The same protein that built muscle when you were 25 triggers a weaker response once you're past 40.
And understanding why is going to change the way you eat.
So let me explain what's going on inside your muscles.
When you eat protein, your body breaks it down into amino acids.
And one in particular, leucine, is the trigger that tells your muscle cells to start building new tissue.
Leucine activates a signaling pathway called mTOR, and when enough leucine reaches your muscle cells, mTOR switches on and your body starts building new muscle protein.
That's how the protein you eat becomes actual muscle.
Now here's what changes.
As you age past 40, your muscle cells gradually become less sensitive to that leucine signal.
The protein still gets digested and the amino acids still arrive at the muscle, but the response is weaker.
Your body now needs more leucine to get the same activation it used to get with less. this is called anabolic resistance.
And the research puts numbers on this.
A 2021 study of 16 adults over 60, published in the American Journal of Clinical Nutrition, found that the leucine requirement was more than double the current recommendation, and that held for both men and women.
And this is exactly why the standard protein recommendation isn't enough if you're over 40 and training.
The research shows that for adults over 65, you need at least 0.45 to 0.55 grams per pound per day just to maintain muscle.
So here's what I tell everyone I work with.
Aim for one gram of protein per pound of your goal body weight per day, with at least 30 to 40 grams at each meal.
And combine that with resistance training because training restores some of that lost sensitivity.
Your muscles are still capable of responding to protein.
They just need a stronger signal to do it.
The other thing that matters is protein quality.
Higher leucine content means better activation.
Animal proteins like beef, chicken, fish, and eggs have more leucine per gram than most plant proteins.
If you're relying on plant proteins, you'll need even more total protein to hit the same leucine threshold.
The bottom line is that the older you get, the more protein matters, not less.
And spreading it across multiple meals throughout the day keeps that signal active instead of hoping one big meal does the job.
Xoxo
References:
Moore DR, Churchward-Venne TA, Witard O, Breen L, Burd NA, Tipton KD, Phillips SM. "Protein ingestion to stimulate myofibrillar protein synthesis requires greater relative protein intakes in healthy older versus younger men." Journals of Gerontology Series A: Biological Sciences and Medical Sciences. 2015;70(1):57-62.
Szwiega S, Pencharz PB, Rafii M, et al. "Dietary leucine requirement of older men and women is higher than current recommendations." American Journal of Clinical Nutrition. 2021;113(2):410-419.
Bauer J, Biolo G, Cederholm T, 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;14(8):542-559.
Burd NA, Gorissen SH, van Loon LJC. "Anabolic resistance of muscle protein synthesis with aging." Exercise and Sport Sciences Reviews. 2013;41(3):169-173.
