What is carb cycling? An expert on how to do it right, and who shouldn't do it

Though carb cycling, along with things like intermittent fasting and body recomposition, used to be a dietary concept followed among weight trainers and elite athletes, it's become mainstream in recent years and is one of today's most popular fitness and nutritional trends. 

Celebs like Kim Kardashian, Kumail Nanjiani and Julianne Hough have gotten in on the action, and celebrity personal trainer David Kingsbury, whose clients include the likes of Jake Gyllenhaal and Hugh Jackman, has said he "swear(s) by it." 

But experts say carb cycling isn't for everyone, and that one needs to keep a few things in mind when considering cutting carbs for extended or even short periods of time. 

What is carb cycling?

Though there is no formal definition for carb cycling, the concept is about adjusting one's consumption of carbohydrates − nutrients that give the body energy − to meet individual dietary needs and athletic goals. "It's a dietary approach that includes increasing one's carbohydrate intake on some days and limiting carb intake on other days," explains Camilla Madziar, MPH, LDN, a registered dietitian and assistant director for the Center of Applied Nutrition at UMass Chan Medical School. 

While many people carb cycle, "it's frequently used in the fitness and bodybuilding communities to optimize fat loss, muscle gain, and/or athletic performance," says Jen Messer, MS, RDN, a nutrition consultant and registered dietitian at Jen Messer Nutrition. Such individuals usually plan their carb cycling days around their training schedule "where high carbohydrate intake is on high-intensity exercise days and lower carbohydrate intake is on less active days," explains Madziar. 

Carb cycling schedules

There are three approaches to carb cycling: daily, weekly and meal-by-meal. 

• The most popular approach is alternating daily between high-carb and low-carb days. "On high-carb days, individuals consume more carbohydrates to fuel intense workouts and replenish glycogen stores," says Messer. On low-carb days, also called a rest or recovery day, "carbohydrate intake is reduced, and the focus is on consuming more proteins and healthy fats." 

• Instead of carb cycling daily, some prefer a weeklong approach. "This involves 3-4 days of higher carbohydrate consumption followed by 3-4 days of lower carbohydrate intake," Messer explains. She adds that in this scenario as well, high-carb days "are strategically placed around intense training sessions, while low-carb days are used to promote fat burning."

• The third approach is known as targeted carb cycling and occurs throughout one's day. "This involves consuming higher amounts of carbohydrates before, during or after workouts while keeping the rest of the day's meals lower in carbohydrates," explains Messer. "This approach aims to provide fuel for intense training sessions, enhance performance, facilitate post-workout muscle recovery/protein synthesis and replenish glycogen stores." Athletes who engage in high-intensity training (HITT) often employ this third method.

What are the benefits of carb cycling?

Many health benefits have been attributed to carb cycling, including enhanced athletic performance and improved muscle recovery, says Messer. "There is also limited research indicating that adjusting carbohydrate intake may help, modestly, in preventing metabolic adaptation, where the body slows down the fat-burning process in response to a continuous calorie deficient," she adds. 

But both she and Madziar say such research is not robust. "Currently, there is limited scientific research on the benefits and long-term implications of carb cycling," says Madziar. "Endurance athletes and bodybuilders use carb cycling as a shorter-term diet plan to potentially help with improving body composition and athletic performance during high-intensity training and competitions...but more research is needed on the safety and efficacy of using carb cycling."

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Is carb cycling better than no carbs? 

Though carbohydrates are essential nutrients, some popular diets such as the keto diet and parts of the Atkins diet suggest cutting them out completely or keeping them very low. While such diets may help one lose weight in the short term, dropping carbs completely for extended periods of time has been shown to cause low blood pressure, kidney stones, constipation, nutritional deficiencies and increased risk of heart disease, per The University of Chicago Medicine. 

Because of this, the experts say carb cycling is preferred over no carb diets, but neither is considered to be the best long-term health strategy.

It's also important to note that not all carbs are the same. Complex carbohydrates are considered good carbs because they are lower in calories and found in healthy foods such as fruits, vegetables and whole grains. Refined carbs, on the other hand, are found in donuts, cookies, and anything made with refined white flour and added sugars. "Cutting out refined carbs is generally good for metabolic health," explains Dariush Mozaffarian, MD, dean for policy and Jean Mayer Professor of Nutrition at the Friedman School of Nutrition Science and Policy at Tufts University. "But avoiding all carbs...isn’t optimal for health in the long run," he says.

Messer agrees and says that carb cycling may have its place for some people, but shouldn't be one's only dietary strategy. "It's important to keep in mind that carb cycling should be used alongside a well-balanced dietary intake that involves monitoring adequate total calorie intake, consuming quality food sources, and ensuring adequate protein intake for muscle maintenance, repair and injury prevention," she advises. "Consult with a registered dietitian or board-certified specialist to understand if carb cycling aligns with your specific needs and goals." 

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