Carb Cycling Diet—What Is It? Does It Work?

By: Lainey Younkin, M.S., R.D.

Learn what it means to cycle your carbs and if you should try it.

carb cycling

Carb-cycling diets gained traction with bodybuilders, but they've recently gone mainstream. Keep reading if you're wondering what carb cycling is, if it's good for you or not, and what to eat if you are carb cycling.

What Is Carb Cycling?

Carb cycling is a method of eating carbohydrates in which you alternate how many carbs you are eating each day—high, moderate or low—based on your workouts and long-term goals. The thinking is that your low-carb days put you in a fat-burning state and eating high-carb boosts your metabolism.

Carbohydrates are the body's main and preferred source of energy. Low-carb diets have long been followed for weight loss, and research shows that compared to low-fat diets, low-carbohydrate diets can lead to greater weight loss in the short term. The caveat is that low-carb diets are difficult for most people to follow long-term.

It's also tough to eat low-carb if you exercise frequently, and low-carb diets are difficult for endurance athletes and bodybuilders who rely on carbohydrates to fuel their workouts. Carb cycling is a solution for elite athletes where they can alternate carbs based on their training schedule. It's also becoming a popular strategy for those trying to lose fat or get past a weight-loss plateau while still staying active.

What Does the Science Say About Carb Cycling?

Unfortunately, not much. There aren't many controlled studies directly investigating carb cycling. The thinking behind carb cycling comes from other weight-loss approaches—like calorie restriction and the ketogenic diet—combined with the science around fueling workouts and burning fat.

Carb cycling tries to match the body's need for glucose. If you've got a longer, more intense workout or race, you need more carbs beforehand (i.e., "carb loading"). If it's a rest day, not so much. The rationale behind carb cycling is that you don't need as many carbohydrates on the days you aren't racing or doing an intense workout, so you can cut back on carbs on these days while keeping protein and fat about the same or eating a little more fat.

Benefits of Carb Cycling

Weight Loss

As with any diet that restricts calories, carb cycling can help you lose weight.

There's one 2013 study, in particular, published in the British Journal of Nutrition, that shows promise. When 33 overweight women ate a carb-cycling-type diet for 3 months they lost about 2¾ pounds more and burned significantly more fat than their 27 counterparts who simply cut calories. Interestingly, both groups ate the same number of total weekly calories, but how they met that target differed: the carb-cycling group cut their calories pretty heavily just 2 days a week and ate "normally" 5 days a week, while the other group cut their calories by 25 percent every day.

However, it may not be the best long-term weight-loss strategy, as it can be challenging to maintain.

Stronger Muscles

The high-carb days (also called "re-feeding") are also in place to refuel muscle glycogen, which may improve performance and reduce muscle breakdown.

Improved Fat Burning

The low-carb days are reported to switch the body over to a predominantly fat-based energy system, which may improve metabolism and the body's ability to burn fat as fuel in the long term.

Better Blood Sugar

Another big component of carb cycling is how it affects insulin. Having low-carb days and targeting carbs around the workout may improve insulin sensitivity. This approach can help maximize the benefits that carbohydrates provide.

Drawbacks of Carb Cycling

Carb cycling is not easy, and some argue that it should be reserved for elite endurance athletes rather than just anyone trying to lose weight. That's because it's difficult to know how many carbohydrates to take in on low-, moderate- and high-carbohydrate days. Some low-carb days have about 2½ to 5 servings of carbs while high-carb days have 10 to 20 servings. It's also time-consuming because you have to track carbohydrates, protein and fat. If you do not track your carb intake carefully, you could fall off track.

There's also the risk, as with any diet, of developing an unhealthy relationship with food. On low-carb days you might find yourself craving high-carb foods throughout the day, and then when your high-carb day comes around there's a risk that you may binge on them. Also, this diet doesn't take an individual's appetite into consideration. Some people find that on heavy training days they don't have as much as an appetite as on rest days. And trying to eat super-low-carb on a day when you have a larger appetite is not sustainable.

Lastly, it could be hard on your digestive system. While varying your diet is not necessarily a bad thing, too much variation can cause gastrointestinal distress for some people.

Is Carb Cycling Ketogenic?

Carb cycling is not the same as the ketogenic diet. The ketogenic diet limits carbohydrates to 20-40 grams each day in order to keep the body in a state of ketosis, where it's burning fat for energy instead of carbohydrates. In contrast, carb cycling alternates the number of carbs eaten each day. You can't follow both diets simultaneously because on a high-carb day, you would throw your body out of ketosis.

What Should You Eat If You're Carb Cycling?

Pictured Recipe: Apple-Cinnamon Quinoa Bowl

If you decide to give carb cycling a try, do it under the guidance of a professional, like a registered dietitian. That expert can give you the exact number of carbohydrates you need each day based on your workout schedule. It may look something like this:

Day 1: Rest day, low carbs (30-50 grams)

Day 2: Moderate workout, moderate carbs (100 grams)

Day 3: Intense workout, high carbs (200 grams)

Day 4: Moderate workout, moderate carbs (100 grams)

Day 5: Rest day, low carbs (30-50 grams)

On high-carb days, keep the carbs healthy. Skip refined, sugary foods and go for whole foods like sweet potatoes, oatmeal, whole-wheat bread, brown rice, fruit and quinoa. These starches are high in fiber and have a more complex carbohydrate structure, requiring your body to burn a bit more energy to break them down. Choose lean protein sources such as chicken, turkey, eggs, fish, nuts, seeds, legumes and soy products.

On low-carb days, limit fruits and starchy vegetables. You can still eat low-carbohydrate vegetables like leafy greens, eggplant, tomatoes, broccoli, peppers, cauliflower and avocados. You should also aim to get plenty of protein, as well as healthy fats like olive oil, nuts, seeds and fatty fish.

Bottom line

Carb cycling is an eating plan used in the short term by endurance athletes and bodybuilders to alternate carbohydrate intake based on intensity and duration of workouts. It can also be followed by people who want to eat low-carb for fat loss but still remain active. Work with a professional to determine how many carbohydrates to eat each day based on your workout schedule, and keep in mind that studies are lacking on the long-term efficacy of carb cycling.

Related:
Low-Carb Foods List
Low-Carb Meal Plans
Ketogenic Foods List