The RDA of 0.8g per kg is a minimum to prevent deficiency — not an optimal intake for body composition or healthy ageing. For active adults trying to preserve muscle while losing fat, 1.6–2.2g per kg is where the evidence lands. Here's how to apply it.

The Evidence-Based Range

A 2017 systematic review and meta-analysis of 49 studies found that protein intakes beyond 1.62g/kg/day produced no additional gains in muscle mass in resistance-trained individuals. A practical ceiling. But for fat loss — where caloric restriction reduces muscle protein synthesis — the optimal range shifts higher: 1.8–2.4g/kg/day during a cut helps preserve lean mass significantly better than lower intakes at matched calorie deficits.

For older adults (50+), the anabolic resistance of ageing means higher intakes are genuinely beneficial: 1.6–2.2g/kg is well-supported as a target for maintaining muscle mass and strength. The much-cited RDA of 0.8g/kg was derived from studies measuring nitrogen balance in sedentary adults — not a meaningful target for anyone trying to maintain or build muscle.

1.62g
Per kg/day: threshold above which no additional muscle gain occurs in meta-analysis of 49 resistance training studies
2.0–2.4g
Per kg/day: recommended range during a calorie deficit to maximally preserve lean mass
30–40g
Per meal: amount that maximally stimulates muscle protein synthesis — beyond this has diminishing returns per sitting

Distribution Matters More Than Timing

Muscle protein synthesis (MPS) is stimulated by leucine — the key branched-chain amino acid. To maximally trigger MPS, you need approximately 2–3g of leucine per meal, which is found in roughly 30–40g of complete protein. Spreading protein across 3–4 meals of 30–40g each produces better muscle protein synthesis over the day than eating the same total in 1–2 large meals.

The old "anabolic window" of 30 minutes post-workout has been largely debunked by more recent research. Total daily protein and per-meal distribution matter far more than precise timing. That said, protein with or around training (within a few hours) is sensible — just not a strict requirement.

Practical Targets by Goal

Maintenance (active, not trying to change composition)

1.4–1.6g per kg of bodyweight. A 75kg person: 105–120g/day. Three meals of 35–40g protein each.

Fat Loss (calorie deficit, preserving muscle)

1.8–2.2g per kg. A 75kg person: 135–165g/day. Prioritise protein to protect lean mass during the deficit. Protein also has the highest thermic effect of any macronutrient — ~25–30% of calories are used in digestion.

Muscle Building (surplus or maintenance)

1.6–2.0g per kg. A 75kg person: 120–150g/day. Beyond 2.0g/kg adds no additional benefit in most research. Focus on quality sources and per-meal leucine adequacy.

Over 50 or Sedentary

1.6–2.2g per kg. Anabolic resistance increases with age, meaning you need more protein to produce the same muscle protein synthesis response as a younger person. This is one of the most important nutritional interventions for healthy ageing.

Best Protein Sources

Animal proteins (meat, fish, eggs, dairy) contain all essential amino acids and high leucine content — they are the most efficient proteins for muscle protein synthesis. Eggs are essentially perfect protein on a leucine-per-calorie basis. Salmon provides 34g of protein per 150g serving plus omega-3s. Greek yoghurt (15–20g per serving) is an easy, high-protein, high-calcium option.

Plant proteins can absolutely meet daily targets, but require more planning: combine sources (legumes + grains) or use pea/soy protein isolate (both complete amino acid profiles). Leucine content of plant proteins is lower, so hitting the same MPS response may require 20–30% more total protein.

Key Takeaways

  • The RDA of 0.8g/kg is a minimum to prevent deficiency — not an optimal target for body composition or ageing well.
  • For active adults: 1.6–2.2g/kg daily. During a fat-loss cut: up to 2.4g/kg to maximally preserve lean mass.
  • Distribute across 3–4 meals of 30–40g each — this produces better muscle protein synthesis than eating the same total in fewer, larger meals.
  • Beyond 1.62g/kg, additional protein produces no extra muscle gain in resistance-trained people at maintenance calories — but does protect muscle during a deficit.
  • Animal proteins are most efficient for MPS due to leucine content. Plant-based eaters should aim for the upper end of the range and prioritise complete sources.
  • Over 50: 1.6–2.2g/kg is particularly important — anabolic resistance increases with age and protein requirements rise accordingly.