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  • Carb cycling is an eating pattern that's emerged as a less strict alternative to low-carb dieting.
  • The basic idea is to eat low-carb diet most days but add in extra carbs on days that you're active.
  • This approach may make workouts feel easier while you're dieting, and is said to support wight loss efforts, too.
  • A dietitian told INSIDER that carb cycling may be unsustainable and detrimental to your relationship with food.

Low-carb diets have been around for decades (remember Atkins?) but they're still popular among people trying to lose weight. The keto diet, in particular - an eating pattern famous for its punishingly low carb allowance - is often touted as a way to drop kilos quickly.

But if a rigidly low-carb lifestyle isn't for you, there is a more moderate approach to carbohydrate consumption that may still aid weight loss efforts, as registered dietitian Christy Brissette wrote in the Washington Post last month. It's an eating pattern known as carb cycling.

See also: Low-carb diets might not be the healthiest for a long life — 2 big new studies suggest they're linked to a higher risk of death

The gist of carb cycling is simple: You stick to a low-carb diet on most days but add in extra carbs on days that you're active, registered dietitian Georgie Fear, author of Lean Habits for Lifelong Weight Loss, told INSIDER. The idea is that carb cycling allows for some food flexibility and makes workouts easier while you're dieting.

But it may have significant drawbacks, too, Fear said. Here's what you need to know about it.

Carb cycling can be different for different people

Broadly, carb cycling is defined as eating an overall low-carb diet but adding in extra carbs on some days, particularly days when you exercise.

Beyond that, the diet is tougher to pin down.

That's because there is no standardised method of carb cycling, Fear said - different people may add different amounts of carbs and have different numbers of higher-carb days. In fact, some people may not adjust carb intake day to day but carb cycle in longer intervals, like weeks or months, Healthline reports. (But the internet has no shortage of suggested carb cyclingmeal plans if you want to peruse some examples.)

The diet is supposed to help with weight loss and make workouts a little easier - but research is lacking

Carb cycling's purported benefits are two-fold.

First, low-carb eating may help you lose weight by making it easier to create a calorie deficit - that's when you burn more calories than you eat.

"The lower carb days are when it's possible to create a larger calorie deficit, because the person can focus on eating lots of protein-rich and vegetable-based meals, which tend to be lower calorie," Fear said. "Reducing carbohydrates is a means to achieving a lower calorie intake. When we eat fewer calories than we expend, we burn stored body fat."

Secondly, the high-carb days can help your workouts feel less miserable.

See also: Scientists are figuring out why fasting helps people live longer — and they say a pill may one day trigger the same benefits

"We do know that reduced carbohydrate eating increases the RPE, or the rate of perceived exertion, during exercise," Fear said. "In short, it makes your workouts feel harder if you don't have enough carbohydrates."

Adding extra carbs on your active days helps alleviate this effect. This concept, by the way, is far from revolutionary.

"The idea of adding extra carbohydrates to exercise has been a staple of sports nutrition for decades," Fear said.

Unfortunately, Fear added she's not aware of any existing research on the effects of carb cycling diet. And in the Washington Post, Brissette wrote that carb cycling's benefits are still "theoretical." There's research on low-carb dieting and the effects of carb-loading in athletes, she wrote, but not on what happens when you alternate between the two.

Finally, it's good to keep in mind that low-carb diets in and of themselves don't magically make you shed kilos. Fear stressed that a calorie deficit is still the most important factor for weight loss, and carb cycling won't help you lose weight if you're consistently consuming more calories than you expend.

It may not be sustainable in the long run

Fear said that a strict eating pattern like carb cycling is likely not sustainable for most people.

"Eating in ways that are super external - relying on external rules or limits or guideline to choose what we eat - tends to make us rebel after a certain period of time," she said.

She added that carb cycling may even be "detrimental" to your relationship with food.

"It can set up a bit of a transactional mentality where [you think], 'I have to exercise to 'earn' my carbs'," Fear said. "What can happen is, if somebody becomes injured or ill and they're not exercising, they feel like they can't eat high carbohydrate foods, and that's just not a healthy setup."

If you're curious about carb cycling, your best bet - as with any big dietary change - is to ask a doctor or a registered dietitian for guidance. But Fear said that, if you do try it, she recommends sticking to whole foods as your carb sources. That means prioritising things like oatmeal, bananas, and peanut butter sandwiches over foods like gummy bears or jelly beans.

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