Carb Cycling: Strategies, Benefits, Precautions

Carbohydrate cycling, or carb cycling, is an eating pattern that involves alternating intervals of low- and high-carbohydrate intake.

Cycling carb intake could benefit athletic performance. Restricting carbs has also been linked to improved blood sugar, weight loss, and more. However, consuming too many or too few carbs for extended periods can have adverse health effects. Talk to a healthcare provider before significantly changing your carbohydrate intake.

Though there’s no set definition for carb cycling, it involves cycling (switching) between lower and higher carbohydrate intake. Athletes sometimes use carb cycling as a way to improve athletic performance. Your body breaks down carbohydrates into glucose, the primary energy source for cells in your body, such as muscle cells.

An example of carb cycling would be an athlete increasing their carbohydrate intake before a marathon or athletic competition and then reducing their carbohydrate intake on less active days. Studies show that consuming a high-carbohydrate diet (i.e., around 70% of calories from carbohydrates) during the 24-72 hours before intensive exercise can increase power output and exercise performance.

Increasing carbohydrate intake after intensive exercise also repletes muscle glycogen stores, which is essential for muscle recovery and stamina.

The average recommendation for carbohydrate intake is for a person to consume 45-65% of total calories from carbohydrates per day, which equates to 225-325 grams of carbohydrates per day for someone following a 2,000-calorie diet.

A research review looked at ideal carbohydrate intake for people doing strenuous exercise for at least one hour and people doing prolonged exercises (e.g., running, swimming, or bicycling) at an intense effort. Researchers found that to restore muscle glycogen stores fully, these athletes require between 8-12 grams (g) per kilogram (kg) of body weight of carbohydrates per day for 24-36 hours post-exercise, or 3.64-5.45 grams per pound (lb). That equates to 544-817 grams of carbohydrates per day for a 150-pound person.

Though athletes often increase their carbohydrate intake leading up to intensive exercise, such as training or competitions, they typically reduce their carbohydrate intake when their activity levels are lower, such as during regular training sessions.

Other populations may also use carb cycling to help them follow a low-carbohydrate diet long-term, including people trying to lose weight. A low-carbohydrate diet is an eating pattern that provides fewer than 130 grams of carbohydrates—or less than 26% of total calories from carbohydrates—per day. People who find it unsustainable to follow a constant low-carbohydrate diet may cycle their intake to enjoy higher-carbohydrate foods or to support exercise performance (e.g., eating more carbs on days of high-intensity training).

There is no set definition or recommended use for carb cycling, so people may also cycle their carbohydrate intake for other reasons. 

Increasing carbohydrate intake can support muscle health and is helpful for endurance athletes like cyclists and long-distance runners. Most people don’t need to follow an extended high-carbohydrate diet, which is why athletes benefit from targeted increases in carbohydrate intake based on their training and competition schedule.

Increasing carbohydrate intake 24-72 hours before an intensive athletic event, such as a marathon, can support performance and improve stamina. Increasing carbohydrate intake after intensive exercise can also speed muscle recovery. There’s no evidence that carb cycling is effective for health goals other than athletic performance. 

A low-carbohydrate diet is linked to several health benefits, such as better blood sugar control, weight loss, and improved heart disease risk factors. These benefits are associated with low-carbohydrate intake only, not cycling low-carbohydrate intake with higher-carbohydrate intake. 

Cycling periods of lower and higher intake of carbohydrates, such as during carb cycling, might offer some of the same benefits as a standalone low-carbohydrate diet. A person who wants to improve blood sugar control or reduce body weight may choose to cycle a low-carbohydrate diet with a day or two per week of higher-carbohydrate intake to make the diet easier to follow or to enjoy higher-carbohydrate meals.

While carb cycling may work well in traditional low-carbohydrate diets, people following very low-carbohydrate diets, such as the ketogenic diet, may not be able to incorporate high-carbohydrate days. The keto diet involves a carbohydrate restriction of fewer than 50 grams of carbohydrates per day to reach and maintain ketosis, a metabolic state in which the body burns fat for fuel instead of carbohydrates. Increasing your carbohydrate intake would cause your body to fall out of ketosis. 

There are no set guidelines for carb cycling, but some people may follow recommendations to improve athletic performance by increasing their carbohydrate intake before intensive training or competitions. 

For example, when preparing for a competition, an athlete may reduce their training volume while consuming a very high-carbohydrate diet of 8–10 grams/kilogram (g/kg) of carbohydrates per day for 1-3 days to maximize muscle glycogen (energy) stores.

People cycling carbohydrates for other reasons, such as to improve blood sugar levels or support weight loss, may stick to a low-carbohydrate diet for 5-6 days a week and then increase their intake for 1-2 days a week, depending on the type of diet they’re following.

Carb cycling methods may vary considerably. Since there’s no set protocol for carb cycling, you can adjust this dietary manipulation method to suit your specific needs and health goals with the help of a healthcare provider or registered dietitian.

Some athletes can benefit from increasing their carbohydrate intake in specific amounts based on their body weight.

If you’re using carb cycling to make it easier to stick to a low-carbohydrate diet or to improve blood sugar or heart disease risk factors like high triglycerides, you can try a more flexible approach. For example, you could try following a low-carbohydrate diet for five days out of the week and then eating higher-carbohydrate the other two days.

Here’s an example of a low- and high-carbohydrate menu:

Low-Carbohydrate Day:

• Breakfast: Omelette made with two eggs, 1 cup of spinach, and 1 ounce (oz) of cheddar cheese, served with half of an avocado (12.5 grams carbohydrates)
• Lunch: Chicken breast on top of a mixed green salad with grilled vegetables and 1 ounce of feta cheese (16 grams carbohydrates)
• Dinner: Salmon with sauteed broccoli and grilled artichokes (21 grams carbohydrates)

Total carbohydrates: 49.5 grams

High-Carbohydrate Day:

• Breakfast: One cup of oatmeal with 1 cup of blueberries and 1 tablespoon (tbsp) of peanut butter (52 grams carbohydrates)
• Lunch: Chili made with ground chicken and beans, served with a side salad (43 grams carbohydrates)
• Dinner: Quinoa salad made with beans, grilled vegetables, and 4 ounces of chicken breast (89.3 grams carbohydrates)

Total carbs: 184 grams 

Your total carbohydrate goals may vary depending on the reason for your carb cycling. Factors like activity levels and underlying health conditions can also influence your individual nutrient needs.

There are generally no health risks involved with carb cycling as long as it’s done appropriately and safely.

Consuming too few or too many carbohydrates can negatively impact your health. Overconsuming carbohydrates can significantly impact your blood sugar levels, which can be especially harmful for people with conditions like prediabetes and diabetes.

If you have diabetes, it’s best to follow a diet that’s appropriate and effective for managing your blood sugar levels, which may involve carbohydrate restriction. Not everyone with diabetes needs to follow a low-carbohydrate diet.

Very low-carbohydrate diets, like the keto diet, aren’t appropriate for specific populations, such as people with liver failure, pancreatitis, and carnitine deficiency. Diets low in carbohydrates aren’t recommended during pregnancy and breastfeeding unless medically necessary.

Although carb cycling is often recommended as a way to lose weight and achieve other health goals, there’s currently no evidence that carb cycling is appropriate or effective for supporting any other aspect of health besides exercise performance. 

Carb cycling involves alternating periods of low-carbohydrate intake with periods of high-carbohydrate intake. Though variations of this practice may support athletic performance and benefit athletes, there’s no evidence that carb cycling offers any other health benefits. 

There are no set guidelines for carb cycling. If you’d like to try this way of eating, working with a healthcare provider, like a registered dietitian, is best to design a safe and appropriate plan specific to your health needs.