Do you really need carbs for strength training? If you've been lifting weights for any length of time, you've probably heard that carbohydrates are essential for maximizing performance and gains. But what does the science actually say? A 2022 systematic review by Henselmans and colleagues analyzed 49 studies to answer this question once and for all. The findings might surprise you.
The Carb-Strength Connection: What We Thought We Knew
Carbohydrates are often touted as essential for athletes, including those engaged in strength and resistance training. The conventional wisdom suggests that carbs fuel your workouts, help you lift heavier, and support muscle growth. But unlike endurance exercise—where glycogen serves as a key energy source—resistance training relies more heavily on anaerobic glycolysis.
Your body stores glycogen in the liver (80–120g) and muscles (350–700g). During resistance training, muscle contractions draw on these reserves via anaerobic pathways due to limited oxygen availability. If glycogen gets too low, it could potentially impair ATP production, muscle excitation, and calcium release.
Current recommendations for strength athletes range from 4–7g/kg/day to as high as 8–10g/kg/day for "heavy anaerobic exercise." Yet typical intakes often fall short—bodybuilders typically consume 2.8–7.5g/kg/day. But do these guidelines actually improve performance, or are they just another fitness myth?
The Science: What 49 Studies Tell Us
Henselmans and colleagues analyzed 49 studies, grouped into four categories:
- Acute supplementation (19 studies): Testing immediate effects of carbs before or during workouts
- Glycogen depletion studies (6 studies): Depleting glycogen then testing carb repletion
- Short-term dietary shifts (7 studies): 2-7 day changes in carb intake
- Long-term dietary interventions (17 studies): Extended periods of different carb intakes
The participants included strength athletes (39 studies), recreationally active individuals (6 studies), and untrained subjects (4 studies). Here's what they found:
1. Acute Effects: Do Carbs Before or During Workouts Help?
Of the 19 studies testing immediate carbohydrate effects, 13 found no performance boost. Only six showed benefits—and these were mostly in specific scenarios:
- Training in a fasted state
- Workouts exceeding 10 sets per muscle group
No clear dose-response relationship emerged, and one study even highlighted a placebo effect—participants performed better with a carbohydrate meal versus a sensory-matched low-calorie sham, even though they didn't know which was which.
2. Glycogen Depletion: Does Running Low on Carbs Hurt Performance?
Six crossover trials induced glycogen depletion (via cycling or high-volume lifting), then tested carbohydrate repletion (0.4–7.7g/kg). Three studies favored higher carb intake, particularly with:
- Short recovery periods (<4 hours)
- Bi-daily training sessions
However, when studies controlled for total calories, the benefits disappeared. The glycogen depletion in these studies ranged from 19–41%, which wasn't enough to consistently limit performance.
3. Short-Term Effects: Do 2-7 Day Carb Changes Matter?
Seven studies compared high (165–672g/day) versus low (31–346g/day) carbohydrate diets over 2-7 days. None showed performance gains from higher carbs. One actually favored low-carb, but this was likely due to order effects rather than the diet itself.
For typical training volumes (under 10 sets), 24+ hours appears sufficient for glycogen recovery, even on lower carb intakes.
4. Long-Term Effects: Do Chronic Carb Levels Impact Gains?
Seventeen studies tested chronic diets ranging from very low (15g/day) to very high (758g/day) over 3 weeks to 3 months. Fifteen found no carbohydrate impact, including all eight isocaloric/isonitrogenous trials (where protein and total calories were matched).
One study favored high-carb, but it was confounded by an energy surplus. Another favored low-carb for the Wingate fatigue index, but not for strength measures.
Breaking Down the Findings
Across all 49 studies, carbohydrate intake rarely enhanced strength performance. Thirty-nine studies showed no effect, including all 16 isocaloric comparisons. Benefits only emerged in specific scenarios:
- Training in a fasted state
- High-volume workouts (>10 sets)
- Bi-daily training sessions with short recovery
Even in these cases, the benefits often lacked metabolic specificity—meaning placebo effects or hunger suppression might explain the gains, not glycogen replenishment.
Practical Implications: What This Means for Your Training
Based on this comprehensive review, here are the key takeaways:
- For typical workouts (≤10 sets): Carbohydrate intake offers no performance edge in fed states. Your body's glycogen stores are likely sufficient.
- For fasted training: About 15g of carbs pre-workout may help.
- For high-volume sessions (>10 sets): Up to 1.2g/kg/h post-workout may be beneficial, paired with 0.3g/kg protein.
- For long-term gains: Carbohydrate levels (15–758g/day) don't dictate strength gains when energy and protein are matched.
The review suggests that high carbohydrate recommendations (4–10g/kg/day) exceed needs for most strength trainees. Beyond specific niches (fasted training, high volume, or bi-daily sessions), flexibility in carbohydrate intake appears sufficient.
Tracking Your Own Carb Needs
Since individual responses vary, the best approach is to experiment and track your results. Easy Reps can help you monitor:
- Your daily carbohydrate intake
- Performance metrics across different carb levels
- Energy levels and recovery between sessions
Try adjusting your carb intake while keeping protein and total calories consistent, then observe any changes in performance, energy, or recovery.
Conclusion: Challenging Conventional Wisdom
The relationship between carbohydrates and strength training is more nuanced than many fitness enthusiasts believe. While carbs aren't the performance panacea they're often made out to be, they may still play a role in specific training scenarios.
The key is finding what works for your body, your training style, and your goals. Don't be afraid to experiment with different approaches—whether that's higher carbs, lower carbs, or something in between. The science suggests you have more flexibility than you might think.
For the full systematic review, check out Henselmans et al. (2022). The Effect of Carbohydrate Intake on Strength and Resistance Training Performance: A Systematic Review. Nutrients, 14(4), 856. And remember, when it comes to nutrition and training, the best approach is often the one you can sustain consistently.