Food · lesson 2 of 11
Protein — the macro most people under-eat
What protein does, the real per-bodyweight target, quality, and meal timing.
7 min read · reviewed October 2026
Protein is the structural and functional macro. It's not just for muscle — it's the raw material for enzymes, hormones, antibodies, and the constant repair of every tissue. Of the three macros, it's also the most satiating (keeps you full) and the most metabolically expensive to process. For most people, getting enough protein is the single highest-leverage diet change available.
What protein actually does
Dietary protein supplies amino acids to build and repair muscle. This is how you preserve (or grow) lean mass — critical for strength, metabolism, and staying mobile as you age. The amino acid leucine is the key trigger that switches synthesis on.
Protein blunts hunger more than carbs or fat per calorie, and its high thermic effect (~20–30% of its calories spent digesting it) means a chunk is 'lost' to processing. Both make adequate protein a powerful tool for fat loss without misery.
Nearly every reaction in the body is catalysed by an enzyme — all proteins. Antibodies that fight infection are proteins too. Under-eating protein quietly degrades repair, immunity, and recovery.
Collagen in skin, tendons, and bone; keratin in hair and nails; transport proteins in blood. Protein is the body's building material, turned over continuously and needing daily resupply.
How much PROTEIN per day should an active 70 kg / 154 lb adult aim for?
Somewhere between 40 and 200 g.
Reveal the answer →
~112 g (1.6 g/kg)
A solid default for an active adult is about 1.6 g per kg of body weight — for 70 kg that's ~112 g/day. The useful range runs from ~1.2 g/kg (lightly active) up to ~2.0 g/kg (hard training or a fat-loss phase, where extra protein protects muscle). Note this is far above the RDA of 0.8 g/kg, which is a floor to prevent deficiency — not an optimum for an active person.
Protein quality: complete, leucine, and DIAAS
Not all protein is equal. 'Complete' proteins (animal foods, soy) have all the amino acids you need in good proportion. Plant proteins are often lower in one or two — easily fixed by eating a variety.
How it works →
Your body needs nine essential amino acids it can't make itself. A 'complete' protein supplies all nine in roughly the ratios you need. The amino acid leucine is the specific trigger for muscle protein synthesis — you want roughly 2.5–3 g of leucine in a meal to maximally switch synthesis on, which is why per-meal protein amount (not just daily total) matters. Plant proteins tend to be lower in leucine and one limiting amino acid (e.g. lysine in grains, methionine in legumes), so combining sources covers the gaps.
What the studies show →
Protein quality is increasingly scored by DIAAS (Digestible Indispensable Amino Acid Score), which improves on the older PDCAAS by measuring true digestibility at the end of the small intestine. By DIAAS, animal proteins and soy/whey score highest (often >1.0), while most single plant proteins score lower — but a varied plant-based diet with adequate total protein readily meets needs. The practical takeaway: if you eat mostly plants, aim a little higher on total protein and spread sources, and consider that whole-day amino acid balance matters more than any single meal.
Spread it across the day
Muscle protein synthesis responds to a per-meal dose, and there's a ceiling per sitting (~0.4 g/kg, often ~25–40 g). So 3–4 protein-anchored meals beat cramming your whole target into dinner. Distribution is the detail most people miss after they fix total intake.
Build your diet in the app and see whether you're actually hitting your protein target — most people are surprised how far under they start.