If you’ve ever considered going low-carb to lose weight but don’t want to completely break up with pasta, carb cycling—a diet that alternates between high-carb and low-carb days—might be an option.
According to a study published in the British Journal of Nutrition, carb cycling may be an effective approach. The study found that overweight women who ate normally but otherwise restricted their carbs two days per week lost more weight than women on a standard calorie-restricted diet for three months. They also better maintained their weight loss, and improved their bodies’ sensitivity to insulin (which regulates blood sugar).
But carb cycling isn’t for everyone—and it isn’t meant to last forever. Here’s what you need to know.
Your Body On (And Off) Carbs
So, why cut carbs in the first place? “Going low-carb has been shown to be somewhat effective for weight loss in the short-term,” says board-certified sports nutrition specialist Jennifer O’Donnell-Giles, R.D. That’s in large part because reducing carbs is a fast way to shed water weight: For every gram of glycogen (energy from carbs) you stash in your muscles, you store three grams of water with it. So by cutting carbs and depleting some of your glycogen stores, you reduce the amount of water your body holds onto. Hence why many low-carb dieters notice they lost three-to-five pounds pretty quickly, says O’Donnell-Giles.
Your body needs carbs, though, for exercise and muscle-building. Any time you work out—whether it’s running or weight-lifting—at a moderate or high intensity, your muscles use up your glycogen stores to make chemical energy called ATP (adenosine triphosphate), explains Pete McCall, C.S.C.S., host of the All About Fitness Podcast and adjunct professor of exercise science at San Diego State University.
This is the downside to low-carb dieting: It might leave your muscles without the fuel they need to perform and grow. And since muscle is crucial for a fired-up metabolism (the rate at which your body burns calories), many long-term, low-carb dieters find that they gain weight faster after coming off that low-carb diet, says O’Donnell-Giles.
Related: 5 Myths About Your Metabolism—Busted
That’s where carb-cycling comes in. By cycling through no-carb, low-carb, and high-carb days throughout the week, you can support weight loss and muscle-building at the same time. On no-carb and low-carb days, you’ll lose water weight and burn fat, explains O’Donnell-Giles. Then on high-carb days, you’ll refuel those glycogen stores with the energy you need to crush tough workouts.
How To Do It
First things first, here’s what no-carb, low-carb, and high-carb days look like on a carb cycling diet:
No-carb days: On these days, you’ll limit your carb intake as much as possible—often below 30 total grams per day, with some people staying as low as 20 to 25 grams. That means that other than protein (like chicken, fish, and steak) and fats (like nuts), you’ll eat only veggies that are high in fiber and water, says O’Donnell-Giles. And not just any veggies: Only low-carb produce like leafy greens, broccoli, cauliflower, onions, peppers, mushrooms, asparagus, and zucchini are on the menu. But starchy vegetables like winter squashes, potatoes, corn, and legumes—along with fruits and dairy—are all no-gos because they’re higher in carbs.
Low-carb days: On these in-between days, you’ll up your carb intake to roughly 70 to 80 grams per day by adding a serving of starchier veggies, fruits, or grains to two meals. Think brown rice, oatmeal, beans, peas, butternut squash, and sweet potatoes. “But many people still avoid gluten, soy, and dairy, which are higher in carbs,” says O’Donnell-Giles. (A serving of pasta contains between 30 and 40 grams, while a sweet potato comes in around 20 grams.)
High-carb days: On these energy restocking days, prepare to load up on the carb-y goods. You’ll more than double your carb intake to between 150 to 300 grams of carbs, which should be evenly spread throughout your meals. Just make sure to eat your carbs along with protein and healthy fats to slow down their absorption and keep your blood sugar as stable as possible. “If you just ate bagels all day, you’d have really high blood sugar spikes from the fast-absorbed carbs,” says O’Donnell-Giles. This blood sugar rollercoaster can affect your insulin sensitivity and lead to weight gain—and, of course, make you feel sluggish when you crash.
How you organize your no-carb, low-carb, and high-carb days is up to you. Some people continuously cycle through a no-carb day, a low-carb day, and then a high-carb day. Others stay on each carb level for three days before moving onto the next. Some even start the work week with two no-carb days, followed by three low-carb days, saving their two high-carb days for over the weekend, says O’Donnell-Giles.
Just plan to eat most of your carbs during the day, when your body needs them the most, and not before bed, says O’Donnell-Giles. For bonus points, load up on your carbs (along with protein) after you work out. Your body uses the amino acids in the protein and the glucose in the carbs to repair your muscles—and your revved metabolism will help shuttle the nutrients straight to your muscles to help you recover and get stronger.
Common Mistakes To Avoid
Limiting any type of food inevitably cuts out important nutrients, warns O’Donnell-Giles. Many people on carb-cycling diets don’t eat dairy, for example, which means they’re missing out on vitamin D, magnesium, and calcium. Meanwhile, ditching gluten means missing out on B vitamins. With a little planning, you can easily incorporate these foods into a carb cycling diet, especially on those high-carb days, says O’Donnell-Giles. The more balanced and well-rounded you can keep your overall diet, the better.
Replacing fresh, whole foods with processed stuff is another common no-no, says O’Donnell-Giles. “Some people won’t touch a banana, but will make shakes out of a packet,” she says. Swapping natural foods for processed ones—even if they’re more low-carb friendly—isn’t a good move for long-term nutrition and health, so avoid the too-easy temptation of packaged products and stick with natural foods.
When NOT To Carb Cycle
As great as carb cycling may sound for losing weight without suffering through an all-around low-carb diet—it’s not for everyone. Reconsider trying carb rotating if any of the following apply to you:
You’ve been diagnosed with anxiety or depression. When you skimp on carbs, your body produces less serotonin, the neurotransmitter that regulates mood and anxiety levels. According to a paper published in PLOS Biology, the body’s release of insulin triggers the release of serotonin. Without carbs to trigger that insulin spike, your production of the feel-good hormone serotonin may also be affected.
Hence why many low-carb dieters get moody and down in the dumps, says O’Donnell-Giles. For this reason, O’Donnell-Giles recommends that those on antidepressants or anti-anxiety medications avoid low-carb diets.
You have type 1 or type 2 diabetes. When you have diabetes, your body has trouble producing and/or using insulin. “That means you need about 15 to 25 grams of carbs, along with protein and fats, at every meal to keep your blood sugar steady,” says O’Donnell-Giles. Significantly switching up your carb intake throws off insulin levels, she says.
You’re an athlete or workout warrior. If you’re exercising heavily—like running 20 plus miles per week or crushing regular CrossFit® classes—carb cycling will leave you without the fuel needed for the long periods of time spent training. Remember those glycogen stores we talked about? If performance is a priority for you, the energy you get from carbs is even more important. “You can’t go low-carb and run 10 miles and feel good,” says O’Donnell-Giles.
The Verdict On Carb Cycling
Though carb cycling can be less restrictive than all-out low carb diets or other eating plans, it’s likely not realistic in the long-term. While it can help you lose weight initially, your body will eventually adapt: “You can try carb cycling for three to four months, but your body will hit its limit,” says McCall. At that point, you’ll likely plateau and need to reassess your nutrition strategy.
In the long run, O’Donnell-Giles recommends finding the carb middle ground in your diet. Weight loss and maintenance are all about consistency, she says. A steady, moderate amount of carbs (somewhere between the low-carb and high-carb day amount) keeps hormones (like insulin) consistent while helping you feel energetic and satisfied, she adds. Just make sure those carbs come from quality, whole foods.