Carb cycling is exactly what it sounds like: varying your carbohydrate intake based on your activity level. You eat more carbs on days you train hard, fewer on rest days or light activity days. It's a middle ground between constant low-carb eating and eating the same regardless of activity.
Originally used by bodybuilders preparing for competition, carb cycling has found a wider audience among athletes, gym-goers, and anyone wanting to optimise their nutrition around their training schedule.
The Logic Behind It
The approach is based on sound physiological principles:
- Carbs fuel intense exercise - Your muscles store glycogen for high-intensity work
- Recovery needs carbs - Replenishing glycogen after training requires carbohydrates
- Rest days need less fuel - Lower activity means lower carbohydrate requirements
- Protein stays consistent - Muscle maintenance doesn't vary as much day-to-day
Rather than eating the same amount of carbs whether you're running a marathon or sitting at a desk, you match intake to demand. It's intuitive when you think about it - you wouldn't fill your car with the same amount of fuel regardless of the journey.
High, Moderate, and Low Days
Most carb cycling approaches use three tiers:
High Carb Days
Heavy training days. Legs, full body sessions, long cardio, competitions.
Moderate Carb Days
Lighter training. Upper body only, moderate cardio, technique work.
Low Carb Days
Rest days or very light activity. Focus shifts to protein and fats.
For a 75kg person, this translates to roughly 150-225g on high days, 75-115g on moderate days, and 40-75g on low days. The exact numbers depend on your goals, training intensity, and individual response.
A Sample Week
Here's how carb cycling might look for someone training 4-5 times per week:
Example Training Week
What the Research Shows
Direct research on carb cycling specifically is limited, but the underlying principles are well-supported:
- Periodised nutrition improves performance - Matching nutrition to training phases benefits athletes
- Low carb availability enhances some adaptations - Training in a low-glycogen state may improve fat oxidation
- High carb availability supports intense training - Adequate glycogen is essential for high-intensity work
- Protein timing matters less than total intake - Keep protein consistent across all days
A 2018 review in the British Journal of Sports Medicine found that strategic carbohydrate periodisation can enhance endurance performance and metabolic adaptations. However, the authors noted that individual responses vary considerably.
Who Benefits Most
Good Candidates for Carb Cycling
- Athletes with varied training demands (endurance + strength)
- Bodybuilders and physique competitors
- People who train 4+ days per week with varying intensity
- Those who enjoy structure and planning meals
- People who feel sluggish on constant low-carb diets
- Anyone wanting to lose fat while maintaining training performance
Probably Unnecessary For
- Recreational exercisers training 2-3 times per week
- People who find food tracking stressful
- Anyone whose training is very consistent day-to-day
- Beginners who haven't established basic nutrition habits
Practical Implementation
If you want to try carb cycling, start simple:
- Keep protein constant - Aim for 1.6-2.2g per kg bodyweight every day
- Adjust carbs only - Don't complicate it with fat cycling too
- Plan around training - Look at your week and assign carb levels
- Focus on carb quality - Whole grains, fruits, vegetables regardless of quantity
- High carb meals around training - Before and after sessions on high days
- Don't fear low days - You're still eating; just fewer carbs
Don't Overcomplicate It
The biggest mistake is making carb cycling too rigid. If your training schedule changes, adjust your carb days. If you have a social event on a planned low day, it's fine to eat normally. The goal is matching fuel to demand on average, not hitting exact numbers every single day.
Carb Cycling vs. Other Approaches
How does carb cycling compare to other dietary strategies?
- vs. Constant low-carb - Better for high-intensity training performance; more sustainable socially
- vs. Keto - Allows for intense training without adaptation period; more flexible
- vs. Eating the same daily - More aligned with actual energy demands; potentially better body composition
- vs. Intuitive eating - More structured; better for people who prefer clear guidelines
The Bottom Line
Carb cycling is a practical, evidence-informed approach to nutrition that matches your fuel intake to your training demands. It's particularly useful for people who train with varying intensity throughout the week and want to optimise both performance and body composition. The concept is simple - more carbs on hard days, fewer on easy days - though the execution requires some planning. If constant macro tracking feels overwhelming, you probably don't need this level of precision. But if you enjoy structure and train seriously, carb cycling offers a sensible middle ground between eating everything and eating nothing.
References
- Impey, S.G., et al. (2018). Fuel for the Work Required: A Theoretical Framework for Carbohydrate Periodization and the Glycogen Threshold Hypothesis. Sports Medicine, 48(5), 1031-1048. doi:10.1007/s40279-018-0867-7
- Burke, L.M., et al. (2018). Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers. The Journal of Physiology, 596(15), 3377-3395. doi:10.1113/JP275892
- Jeukendrup, A.E. (2017). Periodized Nutrition for Athletes. Sports Medicine, 47(Suppl 1), 51-63. doi:10.1007/s40279-017-0694-2
- Thomas, D.T., et al. (2016). Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. Journal of the Academy of Nutrition and Dietetics, 116(3), 501-528. doi:10.1016/j.jand.2015.12.006
