What Is Carb Cycling and Does it Promote Weight Loss?

Carbohydrates remain a hot topic around weight loss. While carb-restricted diets work for some people, they also have their drawbacks. That may be why other approaches that play with carbohydrate intake without removing it completely — such as carbohydrate cycling — are generating a lot of interest. Originally aimed at advanced athletes, the sports nutrition strategy is becoming more popular among novice athletes and everyday folks looking to lose weight.

“Carb cycling is when you alternate the amount of carbs you consume on a daily, weekly or monthly basis,” explains McKenzie Flinchum, a registered dietitian and certified personal trainer. Most commonly, it means eating a lower carbohydrate intake on some days of the week, and higher carbohydrate intake on others. High-carb days usually correspond with harder workout days, and low-carb days are usually rest days or lighter workout days. (Some people may also mix in “medium” carbohydrate days with moderate activity.)

Carb cycling originally comes from the world of sports nutrition. “For endurance athletes, participating in some training sessions with low-carbohydrate availability appears to cause positive adaptations at the cellular level,” says Conor McCrink, a sports dietitian and certified personal trainer. However, more research is needed to determine whether this translates into real performance benefits, says McCrink.

Other types of athletes sometimes use carb cycling to adapt to training needs. “Athletes will increase carb intake on a high-volume training day and decrease carbs on a rest day because less energy is needed,” explains Flinchum. This practice became more mainstream as people got the idea that changing up carbohydrate intake might be helpful not just for athletes looking to increase performance and/or eat for their needs, but also for regular people interested in weight loss.

Research around “refeed days,” or periodically increasing carbohydrate intake for one or two days, may have helped increase interest in carb cycling. Unlike cheat days, which tend to be free-for-alls where a person eats whatever they want, a refeed day means strategically eating a set amount more than usual, primarily in the form of carbohydrates. The research showed refeed days could increase a satiety hormone called leptin, potentially making lower-carb days feel easier. This research isn’t conclusive, though, McCrink points out.

“Carb cycling may help individuals drop body weight (and fat) quickly, and is often used by physique competitors in the weeks prior to competition,” says Olivia Brant, a registered dietitian certified in sports dietetics.

But the reason carb cycling works for weight loss doesn’t necessarily have anything to do with the carbs themselves. “It’s the calories, not the carbs,” says Glenn Gaesser, PhD, a professor in the College of Health Solutions at Arizona State University. “To lose body fat, you need to burn more calories each day than you consume.” This is also known as a calorie deficit. “You can do this on a low-carb diet, in which you consume fewer carbs and burn more fat,” Gaesser explains. “Or, you can do it on a low-fat diet where you consume less fat and therefore don’t need to burn much fat.”

It’s also worth noting some scale weight loss during carb cycling may actually be due to water weight loss (rather than fat loss). “When you lose weight [rapidly] by drastically cutting carbs, the majority of it — up to 10 pounds — is actually just water,” explains Brant. “Carbs hold onto water in our bodies, so you can expect that as soon as you reintroduce carbs, you’ll gain the water weight back.”

If you’re interested in trying carb cycling for weight loss, here are the qualities that are likely to set you up for the best chances of success:

1. You’re physically active and have a predictable workout schedule. “Since carbs are the body’s preferred source of energy, it would be advantageous to coordinate workouts with high-carb days,” says Flinchum. You may appreciate the extra energy on days when you have an intense workout planned, and your body will be able to put the extra fuel to work.

2. You don’t mind tracking what you eat. “Carb cycling is a more advanced nutritional strategy and will require greater effort,” says McCrink. Most people need to weigh and measure their food to carb cycle and keep themselves in a calorie deficit. For some people, meticulous tracking and weighing can trigger disordered eating.

3. You’ve already mastered basic healthy habits. “My advice to those who are thinking of carb cycling is to ensure the lowest hanging fruit is obtained first,” says McCrink. “For some, this may be managing stress, getting enough sleep or increasing their nutritional knowledge to bring awareness to the calorie content of their food choices. Escalating to advanced methods without proper foundations will not set you up for success long-term.”

4. You don’t mind trying a less-researched strategy. There’s little research that has looked at carb cycling specifically, Gaesser points out.

“If the goal is to lose weight, a negative energy balance [aka consistent calorie deficit] is necessary,” says Gaesser. While there’s no harm in trying carb cycling (provided you check with your doctor first), it doesn’t necessarily have an advantage over other science-backed weight-loss methods. Ultimately, you should choose an eating plan that fits your lifestyle and is sustainable long-term.

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