Ask ten endurance athletes what their protein target is and you'll get ten different answers. 0.8g/kg. 1.2g/kg. 1.6g/kg. Some will say "I just try to eat enough." The variance reflects a genuine scientific debate that has evolved significantly over the past decade, and the consensus has shifted toward higher intakes than most popular nutrition apps recommend.

The outdated RDA and why it's not a target

The Recommended Dietary Allowance (RDA) for protein is 0.8g per kg of bodyweight per day. This is the amount required to prevent deficiency in sedentary adults. It is a minimum floor, not an optimisation target.

For athletes, particularly endurance athletes under high training loads, 0.8g/kg is clearly insufficient. The 2024 International Society of Sports Nutrition (ISSN) position stand recommends 1.4–2.0g/kg/day for exercising individuals, with higher intakes during caloric restriction or periods of increased training load.

Why endurance athletes need more protein than expected

Endurance athletes often think of protein as a strength-sport nutrient, for bodybuilders and powerlifters, not runners and cyclists. This is a significant misconception.

During prolonged aerobic exercise, amino acid oxidation (using protein as fuel) increases substantially, particularly of branched-chain amino acids (BCAAs). A 2-hour run can oxidise 3–5g of leucine alone. This isn't muscle breakdown, it's normal substrate use, but it increases the daily protein requirement to maintain nitrogen balance.

Beyond fuel, protein is essential for:

  • Muscle damage repair: Eccentric loading in running causes significant muscle fibre disruption. Protein is the substrate for repair.
  • Connective tissue synthesis: Tendons, ligaments, and cartilage all require amino acids for maintenance and adaptation. Collagen synthesis specifically requires adequate glycine and proline.
  • Immune function: High training loads suppress immune function. Protein inadequacy compounds this effect.
  • Haemoglobin production: Endurance athletes have higher erythropoiesis (red blood cell production). Haemoglobin is a protein.
  • Enzyme synthesis: Aerobic metabolism depends on mitochondrial enzymes, all of which are proteins.

Current evidence-based recommendations

Based on the 2024 literature, the following ranges represent current best evidence for endurance athletes:

  • Maintenance phase / moderate training: 1.4–1.6g/kg/day
  • High training load / competition phase: 1.6–2.0g/kg/day
  • Caloric restriction + training (cutting): 1.8–2.4g/kg/day (muscle preservation requires higher intake in a deficit)
  • Master athletes (over 40): 1.8–2.2g/kg/day (anabolic resistance requires higher per-meal doses)

Per-meal distribution matters more than daily totals

The muscle protein synthesis (MPS) response to protein is dose-dependent up to approximately 0.4g/kg per meal (around 28g protein for a 70kg athlete), after which additional protein in a single meal produces diminishing MPS returns, the excess is oxidised.

This means distributing protein across 4–5 meals per day produces greater MPS than consuming the same daily total in 1–2 large servings. Hitting 160g of daily protein via 4 meals of 40g is substantially more anabolic than 160g split between breakfast and dinner.

In practice, this means:

  • A protein-rich breakfast (30–40g), often skipped by endurance athletes
  • A pre-training snack with 15–20g protein if the session is 2+ hours post-breakfast
  • A post-training recovery meal with 30–40g protein within 2 hours of finishing
  • A protein-rich dinner
  • Pre-sleep casein (cottage cheese, Greek yoghurt) shown to increase overnight MPS by ~22% in trained athletes

Food sources and bioavailability

Not all proteins are created equal. The Digestible Indispensable Amino Acid Score (DIAAS) replaces the older PDCAAS as the gold standard metric for protein quality:

  • Highest quality: Whey, casein, eggs, milk protein (DIAAS greater than 1.0)
  • High quality: Beef, chicken, fish, soy (DIAAS 0.9–1.0)
  • Moderate: Legumes, tofu (DIAAS 0.6–0.9)
  • Lower: Most plant proteins in isolation (DIAAS less than 0.7)

Plant-based athletes should aim for the higher end of protein ranges (1.8–2.2g/kg) and combine protein sources to ensure a complete amino acid profile, rice plus legumes, for example.

What this means for your app

Most nutrition apps set protein targets at 0.8–1.2g/kg, the sedentary adult RDA or the lower end of athletic ranges. If you're an endurance athlete with significant training volume, you are almost certainly running below optimal.

Jonno sets your protein targets based on your training volume (synced from Strava), body weight, and goals, defaulting to performance-optimised ranges rather than minimum adequacy thresholds.

The Jonno Agent also monitors your per-meal protein distribution, flagging when you're front-loading or back-loading protein in a way that reduces your MPS window throughout the day.

The science is clear: endurance athletes need more protein than most of us eat, distributed more evenly than most of us manage. The tools to do this accurately are now available.