For how we live.
The muscle-building literature converges on roughly 1.6 grams of protein per kilogram of bodyweight a day, with gains flattening above that — a target well clear of the deficiency floor most official figures quote.
In people with healthy kidneys, trials find high-protein diets do not worsen kidney function. The picture changes for those who already have reduced function, where animal protein may speed decline.
Branched-chain amino acids can nudge muscle protein synthesis and modestly ease soreness, but they cannot build muscle on their own — and a complete protein does everything they do and more.
One cohort tied high animal protein in midlife to higher mortality, yet found the opposite after 65. Guidelines urge older adults to eat more, and plant protein looks best. No trial proves a lifespan effect.
The official figure is 0.8 grams per kilogram of bodyweight a day — but that number is a floor to prevent deficiency, not a target for optimal health, and that distinction drives most of the argument.
The training and creatine at its core rest on strong evidence. The supplement stack around them mostly doesn't — and the SARMs some users add are frequently not even the drug on the label.
Appetite fades with age and malnutrition is common and under-screened. Supplement drinks produce small, real weight gains — and cut deaths mainly in those already undernourished, not everyone.
Pooling 32 trials, researchers found milk, whey, casein, and soy protein lowered LDL and total cholesterol slightly — but the effect shrank once weaker studies were excluded.
The fear that a high-protein diet damages normal kidneys is not supported by the trial evidence. Protein restriction is a therapy studied in people who already have kidney disease — a different question entirely.
Sarcopenia got a formal definition and diagnostic cut-offs. The clinical guidelines that followed back resistance exercise strongly — and are far more cautious about protein powders, vitamin D and drugs.
A meta-regression of 23 hypertrophy studies found total intake the strongest predictor and no timing effect after adjustment. A later network meta-analysis of 116 trials still favours post-exercise, narrowly.
A NHANES analysis of 5,736 US adults over 60 found the benefit of higher protein directionally present and statistically imprecise. A meta-analysis of protein at breakfast found nothing at all.
The 2025–2030 edition was released January 7. It is the first to name highly processed foods, and the first whose saturated-fat arithmetic does not obviously close.