Are Carbs Actually Necessary for Muscle Growth? Glycogen, Insulin, and Hypertrophy

What research says

• Insulin does promote muscle protein synthesis (MPS) and suppress muscle protein breakdown (MPB).
• However, amino acid elevation from dietary protein alone can maximize MPS stimulation — the additional insulin spike from carbohydrates is not always necessary (Staples et al.
• 2011).
• RCTs show that when adequate protein is present, adding carbohydrates does not further increase MPS.
• Carbohydrates indirectly support hypertrophy (energy supply, training performance), but their direct role via insulin, compared to protein, is limited.

What research says

• An RCT by Wilson et al.
• (2020) found that a ketogenic diet produced comparable hypertrophy to an isocaloric, isoproteic standard diet over 12 weeks.
• After keto-adaptation (adaptation to fat as fuel), some studies show partial recovery of performance in endurance and strength tasks.
• However, keto-adaptation takes weeks, and the transition period may temporarily reduce training performance and hypertrophic stimulus.
• Muscle growth on a ketogenic diet is possible, but requires adequate protein and patience during the adaptation phase.

What research says

• Pre-workout carbohydrates enhance glycogen availability and maintain performance, especially for high-volume or prolonged training sessions.
• Whether post-workout carbs + protein produces more hypertrophy than protein alone is contested (Staples et al.
• 2011) — when protein is adequate, carbohydrates' additional MPS enhancement is small.
• Carbohydrates are useful for energy balance and muscle glycogen replenishment, but the "insulin spike strategy" is overstated.