Carb cycling is a dietary strategy that intentionally varies carbohydrate intake across different days based on training intensity. High-carb days coincide with intense training sessions where carbohydrates are needed to fuel performance and replenish glycogen. Low-carb days are on rest days or easy training days where less carbohydrate is needed and the body can rely more on fat oxidation.
The theoretical rationale is sound: matching carbohydrate intake to demand optimises fuel availability when needed while creating a calorie deficit on less active days. This approach attempts to preserve training performance and muscle building potential (through high carb days) while still creating the conditions for fat loss (through low carb days).
A practical carb cycling structure: High-carb training days (heaviest training sessions, typically 3 days per week): 3-5g carbohydrates per kilogram of body weight. Moderate-carb days (moderate training): 2-3g per kilogram. Low-carb rest days: 0.5-1g per kilogram. Protein remains high (2g per kg) on all days. Fat adjusts inversely to carbohydrate (lower fat on high-carb days, higher fat on low-carb days) to maintain appropriate total calories. The complexity of carb cycling is its primary downside - it requires more planning than fixed macros. For most people, the marginal benefit over a consistent moderate-carbohydrate diet with slightly higher calories on training days doesn't justify the additional complexity. It works best for advanced athletes who have exhausted simpler approaches.