The idea of a carb-cycling diet gained traction among bodybuilders, but it's recently gone more mainstream. Here we take a look at what carb cycling is, if it's good for you or not, and what to eat if you are carb cycling.
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What Is Carb Cycling?
Carb cycling, also known as the intermittent low-carb diet, is a method of eating carbohydrates in which you alternate how many carbs you eat 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. People have long followed low-carb diets for weight loss, but a yearlong randomized control trial (RCT) published in the Journal of the American Medical Association in 2018 shows that low-carbohydrate diets are not superior to low-fat diets for producing weight loss. 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 may be 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 RCTs 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, then 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
1. Improved Fat Burning
As with any diet restricting calories, you may notice weight loss in the short term but little to no progress as time passes, meaning you may have hit the plateau in your weight loss journey. The thought is that when you are in a calorie-deficit state, your hormones signal your body to find new ways to minimize weight loss, says a 2019 study in Sports. Leptin, a hormone that helps regulate appetite and calorie expenditure, comes into play, according to a 2021 Cytokine review article. When low levels of leptin are present, this signals to the brain that you are not eating enough, resulting in a chain of physiological changes, including burning fewer calories. This new metabolic state where you burn less is known as adaptive thermogenesis and is described in a 2020 European Journal of Clinical Nutrition article.
The idea behind carb cycling is to prevent the body from adapting to this new metabolic state. In other words, blood leptin levels are increased temporarily on days when you have a larger intake of carbs, which may improve metabolism and the body's ability to burn fat as fuel in the long term. However, more research is needed to further investigate the relationship between carb cycling and leptin levels.
2. Stronger Muscles
Glycogen, the storage form of carbs, is stored in the muscles and the liver as a quick form of energy when needed. When you are on low-carb days during carb cycling, there is limited storage of glycogen. So, the high-carb days (also called "re-feeding") are in place to refuel muscle glycogen, which may improve performance and reduce muscle breakdown.
3. Better Blood Sugar
Another big component of carb cycling is how it affects insulin. A high-carb diet may lead to more spikes in blood sugar levels, so having low-carb days and targeting carbs around the workout may improve insulin sensitivity. This approach may help maximize the benefits that carbohydrates provide.
Drawbacks of Carb Cycling
1. May Go Overboard with Carbs
A carb cycling diet 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 2 1/2 to 5 servings of carb-rich foods, while high-carb days have 10 to 20 servings. It's also time-consuming because you have to track carbohydrates, protein and fat. You could fall off track if you do not track your carb intake carefully.
2. May Develop an Unhealthy Relationship with Food
While carb cycling may be doable in the short term, maintaining this way of eating may be challenging in the long run. As with any restrictive diet, there's also the risk of developing an obsessive focus on healthy eating known as orthorexia according to a 2021 Frontiers in Psychiatry article. 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 appetite as on rest days. And trying to eat super-low-carb on a day when you have a larger appetite is not sustainable.
3. It's Not Safe for Certain People
Carbohydrate cycling is not recommended for people with diabetes or low blood sugar who require a steady source of glucose in the blood. In addition, limiting nutritious foods rich in carbohydrates, such as fortified and enriched grains, may pose health problems, especially in women of childbearing age who are often low in iron and folic acid, and could result in constipation if fiber intake is inadequate.
Is Carb Cycling Ketogenic?
A carb-cycling diet is not the same as a ketogenic diet. The ketogenic diet limits carbohydrates to 20 grams to 40 g each day in order to keep the body in a state of ketosis, where it burns 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.
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Pictured Recipe: Apple-Cinnamon Quinoa Bowl
What Should You Eat If You're Carb Cycling?
If you decide to try carb cycling, do it under the guidance of a professional, preferably a registered dietitian nutritionist (RDN) who will determine the exact number of carbohydrates you need each day based on your workout schedule. It may look something like this:
5-Day Carb-Cycling Meal Plan
Day 1: Rest day, low carbs (30-50 g)
- Breakfast: (7 g carbs)
- Lunch: (12 g carbs)
- Dinner: over riced cauliflower (12 g carbs)
- Snacks: 1 slice Cheddar cheese, 1 cup raspberries (6 g to 8 g carbs)
Day 2: Moderate workout, moderate carbs (100 g)
- Breakfast: Apple-Cinnamon Overnight Oats (41 g carbs)
- Lunch: (25 g carbs)
- Dinner: over 1/2 cup cooked brown rice (30 g carbs)
- Snacks: 1 slice Cheddar cheese, 1 cup raspberries (6 g to 8 g carbs)
Day 3: Intense workout, high carbs (200 g)
- Breakfast: Gingerbread Buttermilk Pancakes topped with one medium banana and 2 tablespoons maple syrup (104 g carbs)
- Lunch: (40 g carbs)
- Dinner: (35 g carbs)
- Snacks: 1/4 cup almonds, 1 slice Cheddar cheese, 1/2 cup raspberries (15 g to 18 g carbs)
Day 4: Moderate workout, moderate carbs (100 g)
- Breakfast: Apple-Cinnamon Overnight Oats (41 g carbs)
- Lunch: (25 g carbs)
- Dinner: over 1/2 cup cooked brown rice (34 g carbs)
- Snacks: 1 slice Cheddar cheese, 1 cup raspberries (6 g to 8 g carbs)
Day 5: Rest day, low carbs (30-50 g)
- Breakfast: (7 g carbs)
- Lunch: (12 g carbs)
- Dinner: Shrimp Cauliflower Fried Rice (10 g carbs)
- Snacks: 1 slice Cheddar cheese, 1 cup raspberries (6 g to 8 g carbs)
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.
The Bottom Line
The carb cycling diet is an eating plan used in the short term by endurance athletes and bodybuilders to alternate carbohydrate intake based on the 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 an RDN 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.
