Sports nutrition concepts once reserved for elite athletes and bodybuilders are becoming completely mainstream: counting macros, eating for body restructuring, and supplement days. While you may not want to use them year-round, they can definitely provide a useful boost when you’re trying to reach a specific fitness goal. The latest once-niche nutrition tactic to enter the mainstream? Carb cycling. Here’s everything you need to know about this practice and how to tell if it’s right for you.
What is Carb Cycling?
Carb cycling, also known as an intermittent low-carb diet, is a method of eating carbohydrates where you alternate how many carbohydrates you eat each day – high, medium or low – depending on your workout and long-term goals. The idea is that your low-carb days keep you in a fat-burning state, while eating high carbs will boost your metabolism.
Carbohydrates are the body’s primary and preferred source of energy. People have long followed low-carb diets to lose weight, and studies have shown that low-carb diets can lead to greater weight loss in the short term compared to low-fat diets. It is important to note that low-carb diets are difficult for most people to follow long-term.
Eating low-carb can also be difficult if you work out regularly, and low-carb diets can be difficult for endurance athletes and bodybuilders who rely on carbohydrates to fuel their workouts. Carb cycling may be a solution for elite athletes who can alternate carbohydrates depending on their training schedule. It has also become a popular strategy for those trying to shed fat or cross a weight loss bottleneck while still staying active.
What’s the Science behind it?
Carb cycling is a relatively new approach to diet.
Its scientific basis is primarily the biological mechanisms behind carbohydrate manipulation.
Few controlled studies have directly investigated carbohydrate cycling diets.
Carb cycling is an attempt to match your body’s need for calories or glucose. For example, it provides carbohydrates before and after your workout or on high-intensity training days.
High-carb days also help your body replenish its supply of muscle glycogen, which may improve performance and reduce muscle breakdown.
Strategic high-carb periods may also improve the function of the weight and appetite regulating hormones leptin and gastrin.
Low-carb days reportedly convert your body to a predominantly fat-based energy system, which may improve metabolic flexibility and your body’s ability to burn fat for fuel in the long term.
Another important component of the carb cycle is the manipulation of insulin.
Low-carb days and carbohydrate goals around exercise may improve insulin sensitivity, which is an important sign of health.
In theory, this approach may support the benefits provided by carbohydrates.
Although the mechanisms behind carb cycling support its use, this approach should still be taken with a grain of salt due to the lack of direct research. More clinical studies with human participants are needed to find out if carb cycling is safe and effective.
What are the Benefits of Carb Cycling?
There is some evidence that carb cycling may contribute to weight loss and health conditions such as type 2 diabetes.
A 2013 study suggests that intermittent energy and carbohydrate restriction may improve insulin sensitivity and body weight.
The participants’ energy and carbohydrate restriction was intermittent for 2 days a week, and they were divided into two groups. The researchers allowed one group to consume protein and fat as needed, but restricted their overall carbohydrate and energy.
The group that was allowed to consume as much protein and fat as they wanted had a similar number of participants who experienced a 5% or greater weight loss.
The study also found that participants continued to lose insulin resistance, lose body fat and have less of the hormone leptin at the end of the 4 months of following the diet.
This study suggests that there may be benefits to following a carb-cycling diet.
What are the Drawbacks of Carb Cycling?
1. May go overboard with carbs
The carb cycling diet is not easy and some believe it should be reserved for elite endurance athletes rather than anyone trying to lose weight. This is because it is difficult to know how many carbohydrates to consume on low-carb, medium-carb and high-carb days. Some low-carb days have about 2.5 to 5 servings of carbohydrates, while high-carb days have 10 to 20 servings. This is also time consuming because you have to track carbohydrates, protein and fat. If you don’t track your carbohydrate intake carefully, you could get off track.
2. May develop an unhealthy relationship with food
While carb cycling may be feasible in the short term, maintaining this way of eating can be challenging in the long run. As with any diet, there is a risk of developing an unhealthy relationship with food. On a low-carb day, you may find yourself craving high-carb foods throughout the day, and then when your high-carb day comes, you risk gorging on them. In addition, this type of diet does not take into account the individual’s appetite. Some people find that their appetite is not as strong on heavy training days as it is on rest days. Trying to eat ultra-low carb on days when your appetite is high is not sustainable.
Is Carb Cycling Right for You?
Carb cycling can be helpful for two main groups, endurance athletes and active people on low-carb diets.
For those who focus on endurance sports such as running and cycling, preliminary evidence suggests that changing carbohydrates throughout the year – especially lowering carbohydrates during high-volume, pre-season training – may help increase muscle glycogen stores and performance after reintroducing carbohydrates. Basically, lowering your carbohydrate intake before you enter the main training season may help your body make better use of carbohydrates when you need to reintroduce them before you reach peak performance levels.
Carb cycling also makes sense for those who are more interested in weight control or fat loss. For some people, consuming a low-carb diet can be helpful in maintaining weight and optimal health. This may be why keto foods continue to be so popular. It is widely believed that low carbohydrate intake will reduce power output during high-intensity exercise, so if you are eating a low-carb diet but want to complete a HIIT or weight lifting workout, for example, carb cycling may be helpful.
While carb cycling is popular among those who follow a keto-like high-fat, low-carb diet, you don’t have to eat a high-fat diet to benefit from carb cycling. You can absolutely cycle carbohydrates in any kind of diet.
In fact, it’s best to avoid carb cycling while on keto, especially if you’re relatively new to this type of diet. Regularly increasing carbs will take you out of ketosis, so if you decide to cycle carbs on a keto diet, I would limit the high carb days to once, maybe twice a week. After all, the point of ketosis is to get your body to use fat as fuel, so getting your body in and out of ketosis kind of defeats the purpose of the diet and may even make it difficult for you to gauge whether this diet is right for you.
How to Do It?
There are many variations of carb cycling, and people implement programs on a daily, weekly or monthly basis.
The amount of carbohydrates an individual eats each day will depend on whether they consume a high-carbohydrate, medium-carbohydrate, or low-carbohydrate meal. Examples of daily carbohydrate loads include:
- Very low carbohydrates: Under 10% of a person’s daily calories will come from carbs.
- Low carbohydrates: Under 26% of a person’s daily calories will come from carbs.
- Moderate carbohydrates: Between 26–44% of a person’s daily calories will come from carbs.
- High carbohydrate: 45% or more of a person’s daily calories will come from carbs.
Here is an example of a weekly carbohydrate cycling diet, based on a person who needs 2,000 calories per day.
|Day||Carb intake||Fat intake||Amount of carbs|
|Monday||High carb||Low fat||225 g|
|Tuesday||Moderate carb||Moderate fat||130 g|
|Wednesday||Low carb||High fat||75 g|
|Thursday||High carb||Low fat||225 g|
|Friday||High carb||Low fat||225 g|
|Saturday||Low carb||High fat||75 g|
|Sunday||Low carb||High fat||75 g|
Each gram (g) of carbohydrates contains 4 calories.
Carb cycling may be a useful tool for those trying to optimize their diet, physical performance and health.
Several studies support individual mechanisms behind carb cycling, although some of the evidence is mixed. More importantly, there are no direct studies investigating long-term carbohydrate-cycling diets in humans.
Rather than a long-term low-carb or high-carb diet, a balance of the two is beneficial from both a physiological and psychological perspective.
If using carb cycling for fat loss, make sure your protein intake is adequate and that you maintain a caloric deficit.
You may want to consider working with a dietitian to find the best program and carbohydrate amounts for you. If you take any medications or have health issues such as diabetes, it is important to consult with your doctor before changing your diet.