Does the Carb Cycle Diet Work? How it Works

If you’re on a weight management journey, you may have heard of the carb-cycling diet.

It tailors your daily carbohydrate intake to match your activity level and is an alternative to a low-carb or ketogenic diet. 

Athletes and very active people often use carb cycling to achieve improvements in body composition and athletic performance.

However, there is limited research on the effectiveness and safety of carb-cycling diets for weight management.

Continue reading to learn more about carb cycling and the science behind the use of this trendy diet for weight loss. 

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What Is Carb Cycling?

Carbohydrate cycling is an eating pattern that involves alternating between a high-carb diet and a low-carb diet each day, depending on your activity level.

It's also known as an intermittent low-carb diet or carbohydrate periodization.

Some elite athletes and bodybuilders use this approach.

There are many different variations of carb cycling, depending on the type of sport or the desired outcome. 

For example, a person may follow a low-carb diet when they are not exercising but increase carbohydrate intake to fuel their increased activity level the next day.

Others may exercise in a carbohydrate-restricted state.

Proponents of the carb cycling claim it helps: 

• Increase muscle mass.
• Burn body fat. 
• Boost athletic performance. 
• Improve metabolic markers, like insulin sensitivity. 

However, a 2021 meta-analysis of carb cycling found that it did not result in improved performance when compared to the traditionally recommended high-carb diet for athletes.

Overall, there is a lack of long-term studies, which are needed to understand this topic fully. 

Carb Cycling For Weight Loss

Carb cycling has also grown in popularity as a weight-loss diet for active individuals who aren’t athletes.

Some people claim that tailoring your carbohydrate intake each day allows you to burn fat at rest while also fueling your exercise properly. 

Carb cycling is considered an alternative to a continuous low-carb diet, where a person restricts their carbohydrate intake every day.

While a continuous low-carb diet may be effective for short-term weight loss, it may have negative metabolic impacts on a person who exercises frequently.

Though carb cycling may work in theory, human studies examining the diet for weight loss are lacking.

Carb cycling is not currently part of the clinical guidelines for weight management.

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How Does Carb Cycling Work?

To understand how carb cycling works, it can be helpful to learn about carbohydrate restriction and how the body responds to exercise. 

Low-Carb Diet Versus Carb Cycling

A low-carb diet is popular for weight management.

‍Research shows some benefits of a low-carbohydrate, high-fat diet, such as:

• Reduced blood sugar and insulin levels.
• Improved insulin sensitivity.
• Greater loss of abdominal fat.
• Appetite suppression.
• Improved lipid panel.

However, there are downfalls to restricting carbohydrates long-term, mainly relating to metabolic function and athletic performance. 

Additionally, when restricting calories to lose weight, it’s common for the metabolic rate to decrease over time, resulting in weight loss plateaus or weight regain. 

The idea behind carb cycling is to give the body periods of adequate carbohydrate intake to prevent this metabolic adaptation and promote long-term weight loss success.

It’s important to note that this claim has not yet been proven in the research. 

How Carb Cycling Works For Exercise

The carb-cycling diet is often recommended for active individuals who are trying to lose weight.

This is because they desire a low-carb diet for weight loss but need carbs to fuel their exercise. 

When you eat carbohydrates, your body breaks them down into sugars, which are absorbed into the bloodstream and then delivered around the body to be burned for energy. 

During exercise, glucose (or sugar) is the body’s preferred fuel source.

As glucose is burned, the body begins to break down glycogen (stored glucose) for energy.

Once the body’s reserve of glycogen is depleted, athletic performance suffers. 

Therefore, decades of research support consuming carbohydrates before, during, and after intense exercise to increase the available fuel. 

Carb cycling has been proposed as a way to follow a low-carb diet to burn fat for weight loss while still reaping the athletic and metabolic benefits of eating carbs. 

What Does The Research Say?

A 2023 study compared carb cycling with intermittent fasting.

The carb cycling group consumed less than 50 grams of carbohydrates per day on seven alternating days across two weeks.

The intermittent fasting group limited calories to 600 per day on two consecutive days per week and ate unrestricted on the other days. 

The two diets resulted in similar reductions in body weight, fasting blood sugar, insulin, and inflammation markers.

Those on the carb-cycling diet experienced increases in LDL and total cholesterol. 

A small 2020 study compared the effects of a carb cycling diet with a standard calorie-restricted diet on healthy young men who participated in strength and aerobic exercises three days per week for eight weeks. 

Both groups had a 500-calorie deficit, but the carb-cycling group ate less than 30 grams of carbohydrates each weekday.

They compensated for this by having high-carb weekend days. 

Researchers found that weight loss results were comparable between the two groups, but the carb-cycling group experienced some loss in lean body mass.

Those on the standard diet experienced improvements in endurance and performance, while the carb cycling group did not.

Additionally, research shows that people who follow low-carb diets lose the same amount of weight on average as those on higher-carbohydrate diets.

While this doesn’t specifically reflect carb cycling, it shows that macronutrient intake doesn’t significantly impact weight loss in the context of a reduced-calorie diet.  

Overall, the limited evidence on carb cycling doesn’t support this diet as a superior weight management strategy when compared with other methods. 

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Is Carb Cycling Safe?

The long-term effects of carb cycling are unknown.

This type of diet may be lower in fiber, contributing to digestive symptoms like constipation and poorer gut health.

Electrolyte imbalances due to fluid shifts may also occur, contributing to short-term side effects and dehydration. 

Further, restrictive dieting is associated with disordered eating.

‍Research shows that people who follow low-carb diets experience more binge eating and food cravings for carbohydrates. 

Because carb cycling includes periods of strict carbohydrate restriction, it may result in overeating and binge eating on high-carbohydrate days.

However, more research is needed to understand this risk. 

Carb Cycling Side Effects

Many people report uncomfortable symptoms after starting a very low carbohydrate diet, such as carb cycling or the ketogenic diet.

These side effects tend to be strongest in the first week and decrease over time. 

When starting a carb cycling diet, you may notice: 

• Headaches. 
• Fatigue and low energy. 
• Nausea.
• Dizziness.
• Brain fog. 
• Digestive symptoms. 

Though less common, some people also experience symptoms like insomnia, irritability, and anxiety. 

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Who Should Avoid Carb Cycling?

Because of the fluctuations in blood sugar levels this type of diet may cause, people with diabetes should exercise caution with carb cycling.

Additionally, it may be difficult for your doctor to accurately dose your diabetes medication if your carbohydrate intake varies significantly from day to day. 

Other populations should use caution with this type of diet, including: 

• Those with an eating disorder history.
• People who are pregnant or breastfeeding.
• Those who are underweight.
• Pediatric patients. 

Is Carb Cycling Right For Me?

As with any diet plan for weight loss, think about how sustainable carb cycling would be based on your preferences and lifestyle.

The best eating plan for you is the one you can follow long-term. 

Carb cycling is a complex and rigid diet that can be very time-consuming.

It typically involves strict monitoring of your macronutrient intake and planning of your food intake.

Additionally, there are no clear guidelines on the most effective way to follow this diet.

It may be confusing to understand which days to implement a low-carb diet and how many grams of carbohydrates you should eat in each phase. 

If you’re trying to manage your weight, talk to your doctor or dietitian about which eating pattern they recommend for you.

Your dietitian can help you understand the optimal amount of carbohydrates you need to meet your health goals. 

Regardless of your carbohydrate intake, you can focus on limiting refined carbs and added sugars while including high-quality carbs that are rich in fiber, such as whole grains, beans, lentils, and starchy vegetables. 

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Takeaway

Carb cycling is a diet that involves timing carbohydrate intake around exercise for optimal body composition and performance among athletes.

People following it alternate between a high-carb intake and a low-carb intake, depending on their activity level each day. 

Some suggest carb cycling can improve weight loss results by allowing a person to burn fat on low-carb days while still properly fueling their exercise on high-carb days. 

However, there is a lack of research to support this theory, and there may be downsides to following a carb-cycling diet for weight management. 

How a Dietitian Can Help

If you have questions about the optimal carbohydrate and macronutrient intakes for you to meet your weight management goals, consider working with a registered dietitian.

Find a dietitian near you who can tailor your eating plan to support your health goals while being sustainable long-term. 

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