If you were to identify one nutritional variable that has the strongest and most consistent evidence base for people who train, it would be protein intake. The research across muscle preservation, body composition, satiety, and recovery points consistently in the same direction: most people eating a typical Western diet are getting less protein than would support their training goals, and the consequences are measurable.

How much

The current evidence for people engaged in regular resistance training supports a daily protein intake of approximately 1.6–2.2 grams per kilogram of bodyweight. For a 75 kg adult, that's 120–165 grams per day.

This is higher than the general population's recommended daily intake (0.8g/kg), which is a floor for basic health, not a target for people who are actively training and trying to maintain or build muscle. The gap between the two is meaningful in practice.

At the upper end of this range and beyond, additional protein produces diminishing returns on muscle protein synthesis. The body is not infinitely able to use protein for muscle-building; excess amino acids are oxidised for energy. Eating more protein than approximately 2.2g/kg provides very little additional muscle-building benefit, though it remains safe and may help with satiety and body composition indirectly.

The leucine threshold

The primary trigger for muscle protein synthesis (MPS) at a meal level is the amino acid leucine. When blood leucine rises above a certain threshold — achieved with approximately 20–40g of protein from a high-quality source per meal — MPS is robustly stimulated.

Below this threshold, MPS is partially activated but not maximally. Above it, additional leucine doesn't further increase the response at that meal.

This has a practical implication: distributing protein across the day in a way that reaches the threshold at each meal is more effective than consuming the same total amount in one or two very large servings. A person eating 30g of protein at breakfast, 40g at lunch, and 50g at dinner crosses the leucine threshold three times. The same 120g consumed as 10g at breakfast and 110g at dinner crosses it once or twice.

When

The post-workout protein window has been discussed for decades, often with more urgency than the evidence supports. The anabolic window — the period during which protein consumption most effectively stimulates post-exercise MPS — is real but wide: probably 4–6 hours around a session, not the narrow 30-minute window sometimes claimed.

For most people training at moderate intensities and eating adequate total protein throughout the day, the timing of protein within a few hours of training is useful but not critical. Total daily intake is a far stronger predictor of outcomes than timing alone.

Where timing becomes more relevant: training in a fasted state (protein before or immediately after is more important), very high-frequency training where the window between sessions is short, and older adults, who show reduced anabolic sensitivity and benefit more from careful distribution.

Practical implications

  • Aim for 20–40g of protein at each main meal
  • Include protein in a meal or snack close to your training session
  • Prioritise high-quality protein sources that provide all essential amino acids: meat, fish, eggs, dairy, and for plant-based eaters, combinations that provide a complete amino acid profile (soy, or complementary sources like legumes and grains)
  • Total daily intake matters more than any single meal's timing