Carb Cycling

Medically Reviewed by Kathleen M. Zelman, RD, LD, MPH on August 08, 2022
3 min read

Carb cycling is a very strict diet used by serious athletes and bodybuilders who want to drop body fat, get more muscle mass, or store more carbs for long-haul exercise like a marathon. It’s becoming more popular with people who want to kick-start weight loss, even though a lot of the weight you may lose would come from water.

Your body needs carbs to work the way it should. Carbs, proteins, and fats are how it gets its energy, measured in calories. But 1 gram of carbs or proteins has only 4 calories, while 1 gram of fats has 9 calories. Experts generally recommend that you get 50% to 55% of your daily calories from carbs, 10% to 15% from proteins, and less than 30% from fats.

Some carbs are healthier than others. They’re found naturally in dairy products and in plant-based foods like beans, grains, fruits, and vegetables. They’re also added to processed foods, as sugars or starches.

When you digest carbs, they break down into glucose, which your body uses for fuel. Once you stop relying on carbs to fuel your body, you might feel fewer carb cravings and have more energy.

Carb cycling involves going back and forth between high-carb days and low-carb days. There may even be “no-carb” days.

You would usually have a high-carb day when you plan on exercising hard. On those days, your body needs more fuel, so you might eat 2 to 2.5 grams of carbs for every pound of your body weight.

You eat fewer carbs on days when you’re less active. On low-carb days, you might eat .5 grams of carbs for every pound of body weight. You may include a "no-carb" day, when you have fewer than 30 grams of carbs for the entire day.

Another option is to follow a plan where you spend 3 days eating a low amount of carbs: about 100-125 grams each day. Then, you spend 2 days eating a high amount of carbs (175-275 grams) on days you are more active.

When you eat food that has carbohydrates and your blood sugar goes up, your pancreas makes more of a hormone called insulin that takes glucose into cells. There, the glucose is either converted into energy, stored for later, or turned into fat.

As cells take in blood sugar, your pancreas signals the cells to release stored glucose, called glucagon. This back-and-forth makes sure your body has the right amount of sugar.

But when you eat a carb-heavy diet, your body can make too much insulin. That can lead to weight gain and a higher chance of things like type 2 diabetes and heart disease.

Taking short breaks to cycle carbs can give your body a chance to burn fat instead of carbs and muscle tissues. But it’s important to remember that if you aren’t doing plenty of exercise or intense training while carb cycling, high-carb days might make you gain weight.

There isn’t a lot of research on the long-term effects of carb cycling, but it’s generally safe to do for a short time. Make sure your overall diet is healthy so you can keep blood pressure, blood sugar, and cholesterol levels under control.

Your carb cycling plan will depend on several things, including your overall health and your exercise goals. Here’s a sample week:

  • Day 1 (high-intensity workout): 175-275 grams of carbs
  • Day 2 (light-intensity workout): 100-125 grams of carbs
  • Day 3 (high-intensity): 175-275 grams of carbs
  • Day 4 (light-intensity): 100-125 grams of carbs
  • Day 5 (high-intensity): 175-275 grams of carbs

When you cut back on carbs for a few days, you might have:

This is called “carb flu,” and it usually doesn’t last long. Drinking water and electrolytes can help.

Because it is extreme, carb cycling isn’t right for everyone. You shouldn’t try it if you are:

Don’t try it if you have adrenal issues, either.

When in doubt, check with your doctor before you start.

Here are some tips to help you pick the carbs that are best to eat:

  • Choose high-fiber fruits and vegetables.
  • Opt for low-fat milk, cheese, yogurt, and other dairy products.
  • Stock up on legumes, including beans, lentils, and peas.
  • Eat lots of whole grains.
  • Limit refined grains, added sugars, and highly processed foods.