Carb Cycling 101: The Benefits, Drawbacks & Who Should Avoid It

Often advertised as an "easier alternative" to low-carb dieting, carb cycling is a (still very restrictive) eating pattern that switches between high-carb and low-carb days throughout the week. But does it really live up to its promises of promoting fat loss and managing blood sugar?

Carb cycling is an eating pattern that involves cycling between low-carb and high-carb days. It's rooted in the competitive weightlifting world. Bodybuilders have long used it as a way to deplete glycogen stores, lose water weight, and optimize exercise performance right before an event.

Over the past few years, as low-carb eating patterns like the ketogenic diet have soared in popularity, carb cycling has become more mainstream.

"Carb cycling is a tool often used for people following a lower-carb diet eating plan like a ketogenic diet that involves alternating the amount of carbohydrates that you consume on different days," explains Will Cole, IFMCP, DNM, D.C., a functional medicine practitioner.

According to Cole, a typical seven-day carb cycling plan might involve cutting your carb consumption for five or six days and then increasing your intake one or two days per week. For athletes, high-carb days often align with their training plan to provide extra fuel for high-intensity or endurance workouts.

Proponents of carb cycling claim that it can promote weight loss, boost energy levels, and even enhance insulin sensitivity. Plus, some note that it can be a more manageable approach to low-carb eating plans by allowing you to enjoy your favorite high-carb foods a few times per week.

"Carb cycling is not the first option that I recommend if you are just starting out on a ketogenic diet, but it can be a great approach for some people who've reached a plateau in their health," Cole tells mindbodygreen.

This approach, sometimes called "keto cycling," involves following a high-fat, low-carb diet, but taking a day or two off each week to cycle in and out of ketosis, a metabolic state in which your body burns fat for fuel instead of sugar1.

Keto cycling is a relatively new concept, meaning there's not a lot of research on whether or not it's actually effective. However, proponents claim that it can make it easier to stick to a keto diet, which could translate to greater weight loss and health benefits long term.

Carb cycling is often used to help enhance endurance and athletic performance, according to Amy Shapiro, M.S., R.D., CDN, a registered dietitian and founder of Real Nutrition NYC.

She explains that high-carb days can increase stored carbohydrates (aka glycogen)3, which serves as the body's main energy source. On low-carb days, the focus is shifted to proteins and healthy fats to help support recovery.

According to Cole, carb cycling might be especially beneficial for women. He explains that your body requires more carbs during certain parts of your cycle and recommends increasing your intake of fiber-rich carbs around menstruation and ovulation.

Although research in this area is still pretty limited, science does show that dietary intake definitely does fluctuate5 throughout the menstrual cycle. This might be due to changes in hormone levels like estrogen and progesterone, which can affect appetite, coupled with variations in the breakdown of carbs, fat, and protein at different points in your cycle.

Your body might also have a higher tolerance for carbs6 during the first half of your cycle, meaning that the period from menstruation to ovulation is the best time to consume carbs.

"Carb cycling is usually used for athletes or bodybuilders who want to change their body composition," says Shapiro, noting that it can be used to reduce body fat and increase muscle mass.

According to one study, intermittently restricting carbs and calories could lead to greater fat loss and insulin sensitivity compared to cutting calories consistently7. Meanwhile, another two-week study showed that reducing carb intake on alternate days was as effective at reducing body weight and belly fat8 as following a low-calorie diet two days per week.

With carb cycling, your protein intake should remain steady (here's how to calculate your ideal protein intake), while your fat intake might fluctuate depending on your daily carb goals.

You should adjust your daily carb goals to fit your daily calorie needs. Shapiro recommends using an online calculator to determine your unique target calorie intake and then subtracting the amount of protein and fat that you need to determine your carb requirements for high-carb days.

"From there, your moderate-carb days are 15-20% less than that number, and your low-carb days are 20-25% less than your moderate-carb day number," she explains.

Low-carb diets typically contain less than 130 grams of carbs2, or less than 26% of total calories from carbs per day.

Although carb cycling is all about sticking to a specific amount of carbs each day, Cole emphasizes that not all carbs are created equal.

Opting for healthy high-carb foods like vegetables, potatoes, brown rice, and beans can help squeeze more carbs into your diet while also bumping up your intake of other important nutrients like fiber, vitamins, and minerals.

Even though carbohydrates may be the main focus of carb cycling, maintaining a healthy overall diet is just as important. For example, fitting enough protein into your daily diet can strengthen immune function9, boost muscle building10, and promote weight management11.

Meanwhile, rounding out your meal plan with healthy fats like omega-3 fatty acids can ease inflammation12, support brain function, and help keep your heart healthy.

"There are a variety of ways to do carb cycling, from daily carb consumption changes to weekly carb refeeding schedules," Shapiro tells mindbodygreen. "The most important part is to see which cycle works best for you, as carb cycling takes a lot of time and commitment."

One of the biggest criticisms of carb cycling is that it isn't enough science to support its efficacy. For example, according to one review of 49 studies13 published in Nutrients in 2022, while some studies found that increasing carb intake could help improve performance after depleting glycogen stores, other studies found no benefits of carb cycling.

Critics of carb cycling also point out that carbs serve as the body's primary source of energy, meaning that decreasing your intake on a regular basis might leave you feeling sluggish and drained—the exact opposite of what you want.

Without proper planning, carb cycling can also make it more difficult to meet your nutritional needs, which may ultimately negate any potential benefits.

At the end of the day, scientific literature on carb cycling is pretty limited. And while there is some research to support carb cycling in some cases—including for promoting weight loss or athletic performance—a lot of studies have turned up conflicting results, and it's unclear whether or not it's any more effective than other eating patterns.

For this reason, we don't endorse carb cycling as a weight loss or athletic performance tool. Many factors can influence how people (particularly women5) process carbohydrates, and it's important to take this bio-individuality into account when making food choices.

Carb cycling is also far from the only way to lose fat or build muscle mass. Reducing your calorie intake, staying active, and reducing your portion sizes are a few more flexible strategies that can help you lose weight14, with no carb counting required. Similarly, ramping up your protein intake can effectively increase muscle growth15 when combined with resistance training.

Cutting your carb consumption may cause some negative side effects16, including fatigue, hunger, constipation, and bloating.