Low-carb diets are often praised for fat loss, better metabolic health, and endurance performance. But when it comes to building muscle or improving high-intensity output—like weightlifting, sprinting, or CrossFit—slashing carbs too much could be holding you back.
A recent scientific review sheds light on how low carbohydrate availability impacts muscle hypertrophy and anaerobic performance. Even with high protein intake and consistent training, limiting carbs can dampen the results you're chasing. You might lift the same weight, but the gains won’t come as fast—or at all.
What the Science Says
This review analyzed findings from multiple clinical trials to assess how low carbohydrate availability (due to diet or under-fueling) affects strength training outcomes and muscle protein synthesis.
Here’s what they found:
-
Burning Muscle for Fuel: When carbs are low, your body starts using more protein—especially branched-chain amino acids (BCAAs) like leucine—as fuel. These are the same amino acids needed to repair and grow muscle. If you're burning them, you're not building with them.
-
Blunted Muscle-Building Signals: Carbohydrates help activate important genetic signals (myogenic regulatory factors) involved in muscle growth. On a low-carb diet, these signals are weaker, reducing your body’s ability to trigger hypertrophy at the cellular level.
-
Less Hypertrophy, Even with the Same Training: Over 8 to 12 weeks, people on low-carb diets gained less muscle mass—even when protein and calories were matched—compared to those on balanced diets. Strength stayed the same, but muscle size didn’t grow as much.
-
Reduced Anaerobic Performance: For high-intensity movements—think sprints, jumps, or big lifts—your muscles rely on glycogen, the stored form of carbs. Low glycogen means less fuel, leading to poorer performance and recovery.
Should You Cut Carbs?
If your goal is fat loss and you're not doing intense lifting or sprinting, you might be fine on a low-carb diet. But if you’re training hard for size, strength, or power, carbs aren’t the enemy—they're your ally.
Carbs don’t just fuel workouts. They enhance recovery, boost muscle growth, and improve performance in explosive, anaerobic sports. Even recreational gym-goers aiming for visible muscle gains will likely benefit from carbs around workouts.
Bottom line: Cutting carbs too low—even if you’re nailing your protein intake and training consistently—can result in smaller gains and reduced performance. Carbs play a crucial role in muscle repair, hormonal balance, and the ability to train hard and grow.
👉 Need to replenish your glycogen stores the smart way?
Check out our full collection of carbohydrate supplements
Fuel your sessions. Feed your muscles. Grow smarter.