How much protein should I eat?

Five answers to what looks like one question. Fung's number is for an adult at or above a healthy weight who is trying to lose, and he explicitly excludes bodybuilding, pregnancy, breastfeeding and childhood from it. Pompa is writing about visible ageing in a general adult reader.

Lyon and Norton are usually writing about people who train, Lyon specifically about adults over 50 losing muscle, and her number rises rather than falls with age. Longo's inverts at roughly 65. Fung is the only one whose number falls while you are losing weight, and with Pompa one of only two who does not raise it for older adults, which is the population where the gap is widest and where the sarcopenia evidence pushes hardest against them. Your age and whether you train decide which of these numbers is addressed to you.

Fung, Longo and Pompa agree on the direction and disagree only on the number, all landing well below the high-protein side, and all three reason from a metabolic mechanism rather than from muscle. Fung, Lyon and Longo all accept that protein requirements rise in growth, pregnancy and deliberate muscle building. Pompa, Norton and Lyon all treat protein quality and distribution across the day as mattering, and none of them recommends the low end for someone recovering from illness or injury.

Nobody here disputes that resistance training is the primary lever on muscle mass; they dispute whether protein is a second lever or a permissive condition.

A randomised trial of protein intake with hard functional endpoints (grip strength, falls, independence) in midlife and older adults, which does not exist for any of these positions. For Fung specifically, the falsifiable piece is his claim that weight loss lowers the requirement: a trial of lean mass retention at 0.6 against 1.6 g/kg during equivalent weight loss would settle it, and the existing literature already leans against him there.

For Pompa, a controlled trial in untrained midlife adults measuring both glycation markers and lean mass at those same two intakes would move him, and nothing short of it will.