The Protein Mistake Most People Over 40 Are Making
Dr Peter Attia says the official protein recommendation is dangerously low for anyone who wants to maintain muscle mass as they age - and muscle mass is the single best predictor of longevity.
Dr Peter Attia is a physician specialising in the science of longevity. His book Outlive became one of the most discussed health books of the past decade, and his central argument cuts against decades of conventional dietary advice: the biggest nutritional mistake most adults make after 40 isn't eating too much fat or too many carbs. It's eating too little protein.
The Problem with the RDA
The Recommended Dietary Allowance for protein is 0.8 grams per kilogram of body weight per day. For a 70kg person, that's 56 grams - roughly the amount in two chicken breasts. Attia argues this figure represents the minimum needed to avoid clinical protein deficiency, not the amount needed to maintain or build muscle mass as you age.
His recommendation for patients: a minimum of 1.6 grams per kilogram of body weight per day - double the RDA. For active individuals or anyone over 50, he pushes it to 2 grams per kilogram. For that same 70kg person, that's 112-140 grams of protein per day - a figure that feels high until you realise what's at stake.
After age 30, adults lose approximately 3-8% of muscle mass per decade. This rate accelerates after age 60. Low muscle mass is independently associated with higher all-cause mortality, increased fall risk, worse metabolic health, and reduced quality of life. [Muscle & Nerve, 2014]
Why Muscle Mass Predicts Longevity
Attia's core insight is that muscle mass isn't about aesthetics - it's about survival. Skeletal muscle is the largest organ in the body by mass. It regulates blood sugar by absorbing glucose from the bloodstream. It provides a metabolic reserve during illness. It protects joints and bones from the falls that kill an alarming number of elderly people every year. A 70-year-old who can get up from a chair without using their hands, carry groceries, and climb stairs has a fundamentally different health trajectory than one who cannot.
The studies Attia cites consistently show that low muscle mass - sarcopenia - is one of the strongest independent predictors of death in older adults, regardless of body weight, body fat percentage, or the presence of other chronic diseases. You can be a healthy weight and metabolically compromised if your muscle-to-fat ratio is poor.
Anabolic Resistance
There's a biological reason why this gets harder with age. A phenomenon called "anabolic resistance" means that older muscles require more protein per meal to trigger the same muscle protein synthesis response that younger muscles achieve easily. A 25-year-old can build muscle on 20 grams of protein in a meal. A 65-year-old might need 40 grams for the same stimulus.
This doesn't mean eating protein becomes less important as you age. It means it becomes more important - and you need higher doses per meal to overcome the diminished sensitivity. Spreading protein across three or four meals, each containing 30-40 grams, is more effective than back-loading it all into one large dinner.
What Counts
Not all protein is equal for the purpose of maintaining muscle. The amino acid leucine is the primary trigger for muscle protein synthesis, and it's most concentrated in animal proteins - eggs, chicken, beef, fish, and dairy. Plant proteins contain leucine too, but in lower concentrations, so you need to eat larger volumes or combine sources to achieve the same threshold.
Attia isn't anti-plant. He's pro-protein. If you're eating a plant-based diet, you can absolutely meet these targets - but it requires more deliberate planning. Tofu, tempeh, lentils, chickpeas, and seitan are the most protein-dense plant sources. Combining them with grains (rice and beans, for example) provides a complete amino acid profile.
The Practical Numbers
For someone weighing 75kg who wants to follow Attia's recommendation of 1.6g/kg:
- Daily target: 120g protein
- Breakfast: 3 eggs + Greek yogurt = ~30g
- Lunch: Chicken breast with salad = ~40g
- Dinner: Salmon fillet with vegetables = ~35g
- Snack: Handful of almonds + protein-rich snack = ~15g
That's 120 grams without supplementation. It requires paying attention - most people dramatically overestimate how much protein they eat - but it doesn't require exotic ingredients or a gym membership. It requires eggs, meat or fish, dairy, nuts, and legumes in sufficient quantities at each meal.
Attia's broader point: the conversation about nutrition has been dominated by what to avoid - less fat, less sugar, less salt. The question most people over 40 should be asking is what they're not getting enough of. For most of them, the answer is protein.