Carb Cycling: Here's How It'll Help Your Body Burn More Fat

Photo by Nabi Tang

In some circles, "carbs" is practically a dirty word. Carbohydrate-laden foods like processed breads and sugary treats have given the macronutrient a bad name, and popular diets like Atkins and keto aim to practically eschew carbs altogether (with effective results). Carbs have a bit of a reputation; when consumed in excess, they're maligned for potentially causing weight gain, inflammation, gut issues, and more.

But the truth is, some carbs actually do play an important role in the body's functions, and there are some healthy, nutrient-packed carb sources that deliver important vitamins and minerals.

It's not quite as black and white as carb detractors would have you believe, and one trendy (yet extreme) eating plan aims to strike a balance in this "carbs are good vs. carbs are bad" debate. It's called carb cycling. The idea is that by playing to carbs' strengths, you can "hack" your body by maintaining just enough carbohydrates to keep your body functioning optimally while losing fat—never too many carbs, and never too little. And while it's not for everyone (even though carbs aren't entirely restricted), it's a powerful short-term tool for fat loss.

According to William Cole, D.C., IFMCP—mbg Collective member and author of the book Ketotarian—"Carb cycling, done properly, can be a good approach, particularly for women and endurance athletes. It’s also a good option if you find yourself at a weight-loss plateau for more than a month. "

Here's what you need to know about carb cycling.

What are carbohydrates?

First, it's important to understand what carbohydrates actually are (negative connotations aside). Alongside protein and fat, carbohydrates are one of the three primary macronutrients. The role of carbs is to provide energy for your body and brain.

Here's what happens when you eat carbohydrates: First, carbs are broken down into sugars during digestion, and those sugars are absorbed into your bloodstream. Then, in response to an increase in blood sugar, insulin is released to shuttle this sugar (now called glucose) to your cells for quick energy to fuel your day.

Carbs are also stored in your muscles and your liver in the form of glycogen (or the stored form of glucose). Excess glucose, however, is also stored as fat, which is where carbs tend to get their bad name.

Are carbs healthy or not?

Not all carbs are created equal, though. Within the carbohydrate category, there are three main types: sugar, starch, and fiber. Sugar is the simplest form, while starch and fiber are known as complex carbohydrates, so they take longer to break down (keeping you fuller for longer). Refined or processed carbohydrates, which are more added sugar than starch and fiber, are where the trouble comes in. These foods carry little nutritional value, explains nutritionist Kevin Libby, president of PH2 Nutrition.

But while processed carbs are worth ditching, whole foods that are rich in carbohydrates are in a league of their own. Think potatoes (both regular and sweet), other starchy vegetables (like butternut squash and carrots), whole grains (like quinoa and brown rice), legumes (like beans and lentils), and even foods that contain natural sugar, like fruit and milk.

These whole foods have nutritional merit by containing important vitamins and minerals. So while the word "carbs" often conjures up images of bread and sugary baked goods, complex carbohydrates do play an important role in a healthy diet for most people, generally.

During a period of carb cycling, these healthy carbs are included some of the time in order to promote short-term fat loss. Here's how it works.

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What is carb cycling?

Carb cycling aims to avoid excess glucose being stored as fat. The process itself sounds simple enough: In its basic form, carb cycling simply refers to the process of taking carbs out of your diet for a short period of time and adding them back in (in cycles).

The idea is to fill the glycogen storage space in your muscles and liver without tipping over into storing excess glucose as fat. It involves several days of "on" days, where healthy carbs are allowed, so you can build up your stores.

This is followed by several low- or no-carb days, during which your glycogen stores in your muscles and liver are purposefully depleted. "When we take the carbs away, your body burns up all the glycogen, so it's forced to burn fat," explains Libby. After a few no-carb days, carbs are reintroduced to replenish your glycogen stores, and the process repeats itself.

Unlike consistent deprivation diets (including calorie-restrictive eating plans), carb cycling is meant to keep your body from going into starvation mode, which is a cue that tells your body it's under threat, so it's time to batten down the hatches by hoarding fat. With carb cycling, "you're always manipulating the physiological pattern to where you never go into that starvation mode," says Libby.

A beginner's carb cycling plan.

While exact carb cycling plans vary based on the individual, a beginner carb cycling plan involves three "carb days" followed by four "off days," says Libby. (Ideally, a beginner carb cycling plan should have three carb days followed by three off days, not four, but this is tricky to maintain in a seven-day week, says Libby.)

In order to burn through glycogen stores and then build them up again, these days need to be in consecutive blocks (so not one day on, one day off). So in a seven-day carb cycling plan, you might want to put your carb days over the weekend and your off days during the week. 

The appropriate amount of carbs to eat on these days depends on the person, explains Libby. "Everybody's liver holds about 70 grams of glycogen," he says—that's pretty consistent. However, that's just the liver. How much muscle mass a person has will determine how much glycogen they can store—the more muscle mass, the more storage space. A good rule of thumb is to keep it to about 100 to 150 grams of net carbs per day, Libby says—that means the grams of carbs minus the grams of fiber.

On carb days, it's also important not to dive into all those carbs at once. Eating large amounts of carbs in one sitting spikes your blood sugar quickly, and the carbs that can't be stored in the cells, muscles, or liver end up being stored as fat, says Libby. (Not to mention, you're in for an intense blood sugar crash later on.) Instead, spread your carbohydrates out throughout the day, tapering them off at night, says Libby. The energy carbs provide will do you more good at breakfast and lunch to keep you fueled throughout the day, he says—they're not as important at dinner (unless you're, say, going for a night run). Dr. Cole would agree with this not going overboard on the carbs sentiment. "Generally, I do not suggest increasing carbohydrates above 150 grams of net carbs, especially in people who tend to have carb sensitivities such as those with insulin resistance, diabetes, inflammatory issues, or those who have more than 10 pounds of weight to lose." he explained.

After three days of filling up your glycogen stores with carbs, the next phase is to deplete those stores by cutting them out altogether—this means four days of eating as close to zero grams of carbs as you can get. Some trainers and nutritionists allow for a small amount of carbs on very high-intensity workout days, he notes, but he prefers to keep it as close to no-carb as possible. (Fair warning: On no-carb days when you work out, you can expect to be a little more fatigued than usual.)

After four no-carb days, it's time to replenish your glycogen stores again for three days, and the process repeats itself. "After you've depleted the carbs, your body is going to be able to store more carbohydrate when you reintroduce them," says Libby.

What to eat during carb cycling.

On carb days, the focus should be on complex carbohydrates, not simple carbs—they'll help keep you filled up longer, and they contain more vitamins and nutrients (like fiber). And on no-carb days, there's more to it than just cutting out sugars and starches—it's important to replace the calories you'd normally get from carbs with fats.

At least, certain kinds of fats. Carb cycling differs from the keto diet in that not all fats are encouraged—saturated fat sources like bacon and cheeses aren't limitlessly green-lit in a carb cycling plan. Instead, the focus is on omega-3 fatty acids. These are found in healthy fat sources like avocados, olives, fish, and chia seeds.

Non-starchy vegetables (like broccoli and leafy greens) are also a staple on no-carb days. These do have some sugars—not enough to make a dent in your daily carb intake but enough to help stimulate brain function (since the brain does need some glucose to function). Vegetables contain cellulose, which converts to glucose, says Libby.

He also recommends a medium-chain triglyceride (like MCT oil) to stimulate neurological function on no-carb days. And, of course, no-carb foods like lean meat and eggs can help keep you filled up. When you reintroduce carbs, Libby also recommends pairing them with a cup of coffee, especially after a workout.

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Who shouldn't try carb cycling.

Carb cycling isn't for everyone. It's not a diet designed to enhance performance; endurance or high-intensity athletes, like serious runners, bikers, swimmers, and triathletes, need carbohydrates to fuel their training. "For people who are training a lot and doing six days a week of hard-core exercise, there's no reason for you to remove your carbs at all," says Libby.

He also advises against carb cycling for anyone who has adrenal dysfunction issues—these people tend to do better with small meals spread throughout the day, containing low to moderate carbs. In addition, if you've tried intermittent fasting and it hasn't worked well for you in the past, carb cycling may also not be for you.

The pros and cons of carb cycling.

The downside of carb cycling is that it requires strict adherence for it to work, and low-carb diets often come along with unpleasant side effects, including headaches, bad breath, weakness, and fatigue.

It's also not meant to be a long-term eating plan. "It's a very structured program—it's not something you would do lifelong," says Libby. He recommends trying it for about six weeks, then taking a break for at least three months before trying it again to avoid messing with your metabolism. Plus, while the mechanism behind carb cycling makes sense, the benefits are also mainly anecdotal since there haven't been many studies on carb cycling specifically.

The upside of carb cycling, however, is that many have found it to be an effective and fast tool for fat loss. It also doesn't require you to cut out carbs completely. So while it's not a lifestyle change, says Libby, it can provide quick results.

Ready to learn more about what anxiety, brain health, and your diet all have in common? Register now for our FREE Functional Nutrition Webinar with Dr. Mark Hyman.

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