Carbohydrate intake has been a hot topic for a long time.

Several successful diets restrict carbs, and some even totally exclude them (1, 2, 3).

But no macronutrient is categorically bad, including carbs. Your carb intake is something that should be tailored to you as an individual (4).

In order to make changes to their overall carb intake, some people now “cycle” their carbohydrates.

This is known as carb cycling.

This article provides a detailed breakdown of the science and application of carb cycling.

Carb cycling is a dietary approach in which you alternate carb intake on a daily, weekly, or monthly basis.

People may use it to lose fat, maintain physical performance while dieting, or overcome a weight loss plateau.

Some people adjust their carb intake from day to day, while others may do longer periods of low, moderate, and high carb intake.

In short, carb cycling aims to time carbohydrate intake to when it provides maximum benefit and exclude carbs when they’re not needed (5, 6).

You can program your carb intake based on a variety of factors, such as:

  • Body composition goals: Some people will reduce carbs during a diet and then add them back during a “muscle building” or performance phase.
  • Training and rest days: One popular approach is a higher carb intake on training days and a lower carb intake on rest days.
  • Scheduled refeeds: Another popular approach is to do 1 day or several days at a very high carb intake as a “refeed” during a prolonged diet.
  • Special events or competitions: Athletes will often “carb load” prior to an event, and many physique competitors will do the same before a bodybuilding show or photoshoot.
  • Type of training: Individuals will tailor carb intake depending on the intensity and duration of a particular training session. The longer or more intense the training is, the more carbs they will consume, and vice versa.
  • Body fat levels: Many individuals will cycle their carbohydrates based on their level of body fat. The leaner they become, the more high carb days or blocks they include.

A typical weekly carb cycling diet may include 2 high carb days, 2 moderate carb days, and 3 low carb days.

Protein intake is usually similar from day to day, whereas fat intake varies based on carb intake.

A high carb day usually means low fat, whereas low carb days are high fat.

Carb cycling is an advanced diet strategy requiring more manipulation and programming than a typical diet. To get it right, it’s helpful to consult a registered dietitian.

Summary

Carb cycling is a dietary approach in which you manipulate your carb intake depending on a variety of factors.

Carb cycling is a relatively new dietary approach.

The science is primarily based on the biological mechanisms behind carbohydrate manipulation.

Few controlled studies have directly investigated carb cycling diets (7, 8).

Carb cycling is an attempt to match your body’s need for calories or glucose. For example, it provides carbohydrates around your workout or on intense training days.

The high carb days also help your body replenish its supply of muscle glycogen, which may improve performance and reduce muscle breakdown (9, 10).

Strategic high carb periods may also improve the function of the weight- and appetite-regulating hormones leptin and ghrelin (11, 12).

The low carb days reportedly switch your body to a predominantly fat-based energy system, which may improve metabolic flexibility and your body’s ability to burn fat as fuel in the long term (8).

Another big component of carb cycling is the manipulation of insulin (13).

The low carb days and targeting of carbs around workouts may improve insulin sensitivity, a vital marker of health (14).

In theory, this approach may support the benefits that carbohydrates provide.

Although the mechanisms behind carb cycling support its use, it’s still advisable to be cautious about this approach because of the lack of direct research. Many more clinical studies with human participants are needed to find out whether carb cycling is safe and effective.

Summary

The proposed mechanism of carb cycling is to maximize the benefits of carbohydrates and teach your body to burn fat as fuel. While this makes sense in theory, more direct research is needed.

The mechanisms behind carb cycling suggest that it can be beneficial for weight loss.

In theory, carb cycling may help you maintain physical performance while encouraging your body to burn fat for energy.

As with any diet, the main mechanism behind weight loss is a calorie deficit, meaning that you eat less than your body burns over a prolonged period (15).

If you implement a carb cycling diet alongside a calorie deficit, then you will likely lose weight.

However, the complex nature of carb cycling may cause confusion and make it difficult for beginners to stick to the plan.

In contrast, many people may enjoy the flexibility of carb cycling. This could probably improve adherence and long-term success for some people.

Summary

Carb cycling may help you lose weight, as long as you maintain a calorie deficit.

Many people believe that carb cycling can be beneficial for muscle gain and physical performance.

The regular high carb periods and targeted carb intake may help improve performance (9).

Consuming carbs around workouts may also aid in recovery, nutrient delivery, and glycogen replenishment (16, 17).

This may promote muscle growth. However, some research suggests carbs are not necessary to build muscle if protein intake is sufficient (18).

While these mechanisms make sense in theory, direct research comparing carb cycling to other diets is needed to provide an evidence-based answer.

In addition, not all research supports the idea that “carb loading” improves athletic performance or muscle growth (19).

Overall, there isn’t enough data to know for sure (20).

Summary

The mechanisms behind carb cycling suggest it can help you optimize performance. However, further research is required.

As mentioned earlier, carb cycling has the potential to provide some benefits.

By having periods of both low and high carb consumption, you may get many of the benefits of both diets, as well as the potential negatives.

Benefits of low carb periods may include improved insulin sensitivity, increased fat burning, improved cholesterol levels, and enhanced metabolic health (8, 14, 21, 22).

High carb refeeds may have positive effects on hormones during a diet, including thyroid hormones, testosterone, and leptin. High carb periods could also reduce inflammation and help your body use iron (12, 16, 23).

These factors may play an important role in long-term dieting success since hormones play a key role in hunger, metabolism, and exercise performance (24).

There may also be downsides to carb cycling. For starters, a complex diet can be hard to maintain. It’s also unclear whether any potential benefits will be long lasting. Plus, there isn’t enough evidence to know whether carb cycling is safe for your health over time (4).

Summary

Low carb periods may provide a number of health benefits, and high carb refeeds can have positive effects on your hormones. The long-term effects of carb cycling are not known.

There are many variations of carb cycling, including daily alterations or longer periods of high and low carb intake.

Here is a sample week in which you regulate your carb intake on a daily basis:

ExerciseCarb intakeFat intakeAmount of carbs
Mondayweight traininghighlow200 g
Tuesdayaerobic exercisemoderatemoderate100 g
Wednesdayrest daylowhigh30 g
Thursdayweight traininghighlow200 g
Fridayweight traininghighlow200 g
Saturdayrest daylowhigh30 g
Sundayrest daylowhigh30 g

Even more so than a typical diet, carb cycling can take a lot of fine-tuning and adjustment along the way.

You can experiment with the number of high carb days per week and the number of grams of carbs per day to find the best approach for your lifestyle, exercise routine, and goals.

If you prefer a low carb diet, you can add carb cycling occasionally in the form of a refeed. Here are some sample low carb plans with occasional high carb blocks:

Low carb periodHigh carb periodAmount of carbs in high carb period
days 1–11days 12, 13, 14200–400 g per day
week 1–4week 5150–400 g per day

As the table suggests, you can either refeed every couple of weeks or do long periods, such as a 4-week low carb phase with a 1-week refeed.

You will also notice that the number of carbs per day can vary drastically — this depends on activity level, muscle mass, and carbohydrate tolerance.

An athlete who trains 3 hours a day or a 250-pound bodybuilder may need the upper limit (or even more), whereas an individual with a more moderate fitness level may need to refeed on only 150–200 grams.

These examples are only suggestions. There is no proven formula or ratio for carb cycling. The best option is to consult a registered dietitian to make a plan that’s tailored for you. Some dietitians specialize in making diet plans for athletes.

If you take any medications or have any health conditions, it’s important to talk with your doctor before making major changes to your diet. Carb cycling may not be appropriate for people with diabetes.

Summary

There are several options for carb cycling, ranging from daily changes to monthly refeeds. Consult a registered dietitian to figure out what works best for you and your goals.

Here are three sample meal plans for low, moderate, and high carb days. Keep in mind that the total carbs per meal in these samples are estimates, not exact numbers. Consider working with a dietitian to draw up a more precise plan that meets your particular needs.

High carb day

  • Breakfast: 3 boiled eggs, 3 slices Ezekiel (or 7-seed/grain) bread, tomatoes, mushrooms, and a side of mixed fruit (60 grams of carbs)
  • Lunch: 6-ounce (oz.) sweet potato, 6 oz. lean meat or fish, mixed vegetables (45 grams of carbs)
  • Pre-workout: 1 serving oatmeal, almond milk, 1 cup berries, 1 scoop whey protein (50 grams of carbs)
  • Dinner: 1 serving brown rice, 6 oz. lean chicken, homemade tomato sauce, 1 serving kidney beans, mixed vegetables (70 grams of carbs)

Moderate carb day

  • Breakfast: high protein yogurt, 1 cup mixed berries, stevia, 1 spoon seed mix (25 grams of carbs)
  • Lunch: 6 oz. chicken salad with 4 oz. diced potatoes (25 grams of carbs)
  • Pre-workout: 1 banana and whey protein shake (30 grams of carbs)
  • Dinner: 1 serving sweet potato fries, 6 oz. lean beef, homemade tomato sauce, 1 serving kidney beans, mixed vegetables (40 grams of carbs)

Low carb day

  • Breakfast: 3 eggs with 3 slices bacon and mixed vegetables (10 grams of carbs)
  • Lunch: 6 oz. salmon salad with 1 spoon olive oil (10 grams of carbs)
  • Snack: 1 oz. mixed nuts with 1 serving turkey slices (10 grams of carbs)
  • Dinner: 6 oz. steak, 1/2 avocado, mixed vegetables (16 grams of carbs)

Some carbs should be enjoyed in moderation, including simple sugars and refined carbs, which are found in foods such as cakes, desserts, highly processed snack foods, and baked goods.

In contrast, there are plenty of healthy carb sources that are tasty and packed full of beneficial fiber, vitamins, and minerals.

When planning your high carb days, focus on these healthier carb choices.

Recommended carbs

Instead of labeling carbs as “good” or “bad,” consider choosing unrefined carbs whenever possible. These include:

  • Whole grains: Unmodified grains are perfectly healthy and may have many health benefits. Examples include brown rice, oats, and quinoa.
  • Vegetables: Every vegetable has different vitamin and mineral content. Eat a variety of colors to get a good balance.
  • Whole fruits: As with vegetables, every fruit is unique, especially berries, which have high antioxidant content and low glycemic load.
  • Legumes: These are a great choice of slow-digesting carbohydrates, which are full of fiber and minerals.
  • Tubers: This category includes potatoes and sweet potatoes.
Summary

Limit refined carbs and added sugars. Instead, eat mostly whole foods that contain plenty of fiber.

Carb cycling may be a useful tool for those trying to optimize their diet, physical performance, and health.

Some research supports the individual mechanisms behind carb cycling, although some evidence is mixed. More importantly, no direct research has investigated a long-term carb cycling diet in humans.

Rather than a long-term low or high carb diet, a balance of the two may be beneficial from both a physiological and a psychological perspective.

If using carb cycling for fat loss, ensure that your protein intake is adequate and you maintain a calorie deficit.

You may want to consider working with a dietitian to find a protocol and carbohydrate amounts that are the best fit for you. And if you take any medications or have health conditions such as diabetes, it’s important to consult your doctor before changing your diet.