What Is Carb Cycling?

Restriction of carbohydrate intake has been a subject of great interest to both the public and the research community.¹ Studies of low-carbohydrate diets such as the ketogenic diet have shown improvements in weight and metabolic profiles through inducing a state of ketosis. However, such diets have largely been scrutinized in the athletic community, with concerns that low-carbohydrate diets do not provide optimal energy supplies needed for short-term, high-intensity physical excursions. To address such concerns, the “carb cycling” method has been suggested as a potential dietary method that plays the advantages of both low- and high-carbohydrate diets to its strength. “Carb cycling” is also referred to as carbohydrate cycling or cyclical ketogenic diet and is characterized by alternating time periods of high and low carbohydrate intake.^1,2

How Does Carb Cycling Work?

Carb cycling aims to allow individuals, especially those seeking to achieve high athletic performance, to consume adequate carbohydrate to optimize physical performance while not affecting the benefits of ketosis under a low-carbohydrate diet.² Studies have suggested that physical training in a state of low glycogen (ie, form of sugar stored in the body) promotes favorable metabolic pathways. However, researchers hypothesize that most studies fail to show that such changes lead to improvements in physical performance because of the lack of carbohydrates needed to sustain physical endurance. It is suggested that consuming carbohydrates immediately before high-intensity physical activity can replenish glycogen supplies to muscles and allow sustained physical performance, while restricting carbohydrate at other times can allow the body to undergo favorable long-term metabolic adaptations.^2,3

What Are the Potential Benefits of Carb Cycling?

Currently, there is limited evidence suggesting that carb cycling is beneficial, with only few studies researching the effects of carb cycling. One study compared the effects of carb cycling vs. even carbohydrate consumption on 11 cyclists in a 1-week intervention.³ Those in carb cycling consumed carbohydrate prior to high intensity training, which was followed by carbohydrate restriction overnight and a low-moderate intensity training during fasting state. The study found that those in carb cycling showed improved performance compared to those who maintained steady carbohydrate consumption, but that no metabolic markers showed any changes. In another randomized controlled trial, cyclical ketogenic reduction diet was compared to a nutritionally balanced reduction diet in 25 healthy young males, with both interventions reducing caloric intake by 500 kcal/day through means of dietary restriction and physical activity.² After eight weeks of intervention, both groups experienced reductions in weight, body fat, and body mass index. However, those randomized to the cyclical ketogenic diet saw more significant decreases in lean body mass and body water. Those in nutritionally balanced reduction diet saw increases in muscle strength and endurance performance parameters, while those in cyclical ketogenic diet did not.

Although the hypothesized biomolecular mechanisms of carb cycling are thought to produce potential improvements in metabolic and athletic performance, the research on this topic is yet inadequate to draw any meaningful conclusions.

How Do Start Carb Cycling?

Those who are interested in starting carb cycling can do so by alternating days or time periods of high and low carbohydrate intake.² Carb cycling can be personalized based on individual needs, but here are some ideas on how to get started.

Alternate Days: You alternate days of high carbohydrate intake of 50-150 g/day and low carbohydrate intake of <50 g/day.² For instance, on Monday, consume a high carbohydrate diet and engage in high-intensity endurance workout. On Tuesday, consume a low carbohydrate diet while engaging in low-moderate intensity aerobic workout. Continue this pattern.

Train High, Sleep Low: You consume high carbohydrate meals before physical training, then restrict carbohydrate intake afterwards and throughout the night.³ For instance, eat a high carbohydrate meal for lunch then engage in a high-intensity endurance workout in the afternoon. Restrict your carbohydrate intake for all your meals afterwards, throughout the afternoon and the evening. Engage in a low-moderate intensity workout in the morning while fasting, then consume your high carbohydrate meal for lunch before engaging in another session of high-intensity endurance workout. Continue this pattern. 

If you have any medical conditions, please make sure to consult with your health care team before making drastic changes to your diet and physical activity routine.