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Carb Cycling: What It Is, How It Works, and Is It Safe?

Natalie Krafft

Published in Nutrition

8 min read

December 26, 2023
plate of low carb foods
plate of low carb foods

In the world of fitness and nutrition, carbohydrate intake is a major focal point for popular diets like the ketogenic or metabolic confusion diet. One you may not be as familiar with, however, is the concept of carb cycling.

Carb cycling is another buzzworthy approach that has garnered attention for its potential to enhance performance and aid in weight management by strategically varying carbohydrate intake.

But while carb cycling is popular among everyone from bodybuilders to endurance athletes, it’s not exactly a suitable approach for everyone. If you’ve ever been curious about this diet and how effective it can actually be, you’re in the right place.

Here’s everything you need to know about carb cycling, who this diet is for, and the potential health benefits and drawbacks you should consider.

What is Carb Cycling?

assorted vegetables
Source: Unsplash

Carb cycling is a short-term dietary pattern that involves varying the amount of carbs you consume on a daily basis, alternating between periods of high and low carbohydrate intake, with intermittent rest days. The main goals of carb cycling include:

The basic premise of this eating plan is that low-carb days can transition your body into a fat-burning state, while high-carb days boost metabolism and restore energy levels. However, it's important to note that the effectiveness of carb cycling can vary from person to person, and it's not a one-size-fits-all approach. 

Although some people may also see weight loss results from carb cycling, there is still a significant lack of scientific research to support its efficacy.

What Is The Difference Between A Keto Diet And Carb Cycling?

The ketogenic diet and the carb cycling diet may seem similar as they are both dietary approaches that consist of manipulating carbohydrate intake. However, they do have some key differences in terms of macronutrient distribution, philosophy, and practice. 

Here are the primary distinctions between these two diets:

  • Carbohydrate intake: Carb cycling alternates between periods of low-carb and high-carb intake to support energy needs and promote fat-burning, while the keto diet aims to limit carb intake to achieve a state of ketosis.
  • Fat intake: Fat intake can vary depending on the day with carb cycling, while the keto diet specifically emphasizes a high intake of healthy fats to compensate for the reduced carbohydrates.
  • Protein intake: The keto diet encourages moderate to high protein intake to preserve lean muscle mass, and carb cycling only suggests consistent protein intake for muscle maintenance and repair.
  • Flexibility: Keto is slightly more rigid when it comes to adhering to consistent high-fat and low-carb diet principles, while carb cycling offers more flexibility by allowing individuals to adjust their carb intake accordingly.

How Carb Cycling Works

carb cycling sample plan

Unlike many diets, carb cycling does not have tailored guidelines and suggestions that you should follow to achieve desired results. As a result, it’s important to remember that results can vary from person to person, based on goals and implementation. Let’s dive deeper into how carb cycling diets work.

Macronutrient Manipulation

Carb cycling involves adjusting not only carbohydrates, but also protein and fat intake to create a balanced, nutritional eating plan. On high-carb days, protein intake remains consistent to support muscle maintenance, while fat intake is lower to accommodate calories from higher carbs. 

On low-carb days, fat intake is often higher due to reduced carbohydrate calories. This ensures that overall caloric intake remains healthy and balanced, while macronutrient ratios are tailored to specific goals like muscle preservation and fat loss.

High-Carb Days

On high-carbohydrate days, you’ll increase your carbohydrate intake while keeping protein consistent  and fat intake low. Carbohydrates provide a readily available source of energy in the form of glucose, which is crucial for fueling high-intensity exercise. 

Since intense physical activity depletes glycogen stores in muscles, high-carb days help replenish these stores, ensuring there is enough fuel available for subsequent workouts. High carb foods include things like whole grains such as white and brown rice, lentils, starchy veggies like potatoes, and fruits like bananas, to name a few.

Low-Carb Days

a plate of shrimp and zucchini
Source: Shutterstock

In contrast, lower carb days involve intentionally reducing carbohydrate intake and usually consist of a higher fat intake to compensate for the reduced calories from carbohydrates.

With reduced carbohydrate intake, the body shifts its primary fuel source from carbohydrates to fat, which can enhance fat burning and may be helpful for weight loss. Alternating between high and low-carb days can potentially support metabolic flexibility,  which is what allows your body to efficiently use fuel from different sources.

Calorie Cycling

With a carb cycling diet, your calorie intake will likely fluctuate between higher-carb days and low-carb days. Typically, high-carb days are associated with higher calories, while low-carb days may result in a calorie deficit, though this isn’t always the case.

When done appropriately, alternating between high and low-carb days can help create an overall weekly or monthly caloric deficit, which is crucial for weight management and weight loss. Some people may choose to intentionally cycle calories in addition to carbs to prevent their metabolic rate from slowing down.

Tailoring Carb Cycling To Goals

a plate of rice and veggies
Source: Unsplash

Carb cycling can be customized to align with individual fitness, weight loss, or muscle-building goals by adjusting the frequency and intensity of high and low-carb days. Here's how carb cycling can be tailored to meet different objectives.

  • Weight loss: Incorporate more frequent low-carb days to create a caloric deficit while also maintaining a balance of protein and healthy fats.
  • Muscle building: Emphasize high-carb days and high protein intake to have the fuel needed for intense workouts and preserving muscle.
  • Fitness/performance: Athletes may place high-carb days around intense training sessions to ensure optimal glycogen stores and sustained energy levels.

Meal Planning And Timing

Structuring your meals and timing them around workouts is a key aspect of maximizing the benefits of carb cycling. For example, on high-intensity workout days, experts recommend consuming a high-carb meal one to two hours before exercising and a post-workout meal or snack with both carbs and protein 30-60 minutes after exercising.

On low-carb days, you’ll want to prioritize a balanced meal with lean protein and healthy fats. While carbohydrates are reduced, fats can provide a slow-burning energy source, while protein helps support muscle recovery.

Are There Benefits to Carb Cycling?

benefits of carb cycling

When done appropriately, and depending on your individual goals and preferences, carb cycling can offer several potential benefits. Common benefits of carb cycling include improved athletic performance, enhanced fat loss, and muscle preservation.

  • Fat loss: Alternating between high and low-carb days may encourage the body to efficiently use both carbs and fats for energy and may improve metabolic rate.
  • Muscle preservation: By strategically placing high-carb days, you can provide your muscles with the necessary glycogen for intense workouts, preserving muscle mass during periods of calorie restriction.
  • Performance improvement: High-carb days supply the body with readily available energy which can enhance performance and improve endurance during high-intensity workouts.

Health Risks for Carb Cycling

risks of carb cycling

Although many who engage in carb cycling see individual fitness benefits like fat loss or muscle preservation, there is unfortunately still a significant gap in the scientific research. Before you dive straight into carb cycling, here are some risks to be aware of.

Hypoglycemia (Low Blood Sugar)

On low-carb days, reduced carbohydrate intake can deplete glycogen stores, which can lead to a significant drop in blood sugar levels. Low blood sugar may result in symptoms such as shakiness, irritability, dizziness, and difficulty concentrating. 

Individuals with diabetes or those prone to blood sugar fluctuations should be cautious when engaging in carb cycling and monitor blood sugar levels closely.

Nutrient Deficiencies

If not carefully planned through a carb cycling meal plan, carb cycling can potentially lead to nutritional deficiencies and imbalances due to variations in macronutrient intake. To mitigate this risk, you should prioritize a balanced approach that includes a variety of nutrient-dense foods, like vegetables, fruits, lean proteins, and healthy fats.

Low Energy Levels 

On low-carb days, carb cycling can potentially lead to reduced energy levels, fatigue, or lethargy most often due to insufficient glycogen stores or nutritional deficiencies. Individual responses to carb cycling can vary greatly, and some people may not adapt as well to periods of low carbohydrate availability, which may result in irritability or mood swings.

Psychological Impact

The restrictive nature of low-carb days can be extremely mentally challenging for some, potentially contributing to feelings of deprivation, food cravings, and mood swings. For those with a history of disordered eating or those susceptible to psychological stress related to food, carb cycling may not be a suitable approach.

Should You Try Carb Cycling?

two people cooking together
Source: Unsplash

While carb cycling may have some potential advantages for athletic performance or weight loss, whether you should try it or not depends on your individual goals, preferences, and health status. The key lies in listening to your body's signals and adjusting the approach according to your body’s needs, rather than adhering rigidly to a one-size-fits-all carb cycling regimen.

It’s important to keep in mind that not everyone may experience the same potential benefits, and while this diet is generally safe if followed wisely, there are some risks involved, including potential disruptions to energy levels and hormonal balance. 

Those with certain medical conditions, such as diabetes, metabolic disorders, or eating disorders, should approach carb cycling cautiously under the guidance of a healthcare professional. Make sure to consult a registered dietitian or nutritionist before making significant changes to your diet such as reducing your daily calorie or carb intake.

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Jordyn Wallerius, MS, RDN, CD

Reviewed by: Jordyn Wallerius, MS, RDN, CD

Jordyn has a bachelor’s degree in biology, a graduate degree in Human Nutrition and completed a dietetic internship at the Memphis VA. She's a dietitian at Nutrisense, and has experience working as a clinical dietitian at a VA medical center specializing in oncology and at the Mayo Clinic, working with a wide range of patients ranging from neonates in the NICU to adult ICU.

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