What to Know About Calorie Cycling

If you've been following a low-calorie diet and splurged one day, you may be surprised to find that you didn't gain any weight. Some dieters do this on purpose. This is often called calorie cycling or calorie shifting, which involves alternating days of low-calorie intake with days of no diet restrictions. 

Can taking a break from dieting actually help you lose weight? Here's what you need to know about calorie cycling.

How Your Metabolism Impacts Weight Loss

Scientists believe that our bodies evolved to protect us from losing valuable calories and nutrients. In the past, lack of food was more common. Since a shortage of calories is a threat to survival, the body evolved to guard against weight loss. When food is scarce, your metabolism slows down, meaning you'll burn calories at a slower pace.

So, when you go on a calorie-restricted diet, your body may think it's in danger of starvation. Your metabolism will slow down in response.

If you go on a low-calorie diet, you may lose weight at first. This can be a good motivator, but after a while, you may struggle to lose pounds. You may regain some weight, even if you've been careful about sticking to your low-calorie diet.

A slowed-down metabolism may not correct itself. One study on the popular weight-loss TV show The Biggest Loser found that participants lost about 40% of their body weight, but also experienced a 23% reduction in their metabolic rate.

Six years after they left the show, the participants gained an average of 90 pounds, but their metabolism remained slow.

What Is Calorie Cycling?

The idea behind calorie cycling is that occasional days of normal caloric intake can keep the body from thinking it's starving. As a result, your metabolism shouldn't be affected, even when you reduce your calories on most other days. 

In one study, one group followed a diet that included calorie cycling. They dieted for 11 days, then ate as they normally would for three days. The other group followed a strict calorie-restricted diet. At the end of the study, both groups lost the same amount of weight. Those who did calorie cycling saw no change in their metabolic rate and kept most of their weight off after the trial ended.

In another study, women spent a month on a low-calorie diet, followed by a month on a moderate diet. They repeated this pattern for five months. Their resting metabolic rate didn't fall, and they lost weight and body fat. They also exercised for three hours a week. It's unclear whether calorie cycling, the exercise, or the combination of both produced the positive results.

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Does Calorie Cycling Work for Everyone?

Although some studies show that calorie cycling can be good for weight loss, research on dieting in general can be difficult for the following reasons:

  • Much research is done with animals, and the results may not apply to humans.
  • In human studies, it's difficult to control what the study participants eat.
  • Humans have different sizes, genders, environments, and genes, all which may affect results.
  • Most human studies don't last long enough to reach meaningful conclusions.

Another problem with testing calorie cycling is that there isn't a set way to do it. There are many different protocols and plans that involve various amounts of calories and days in which to restrict and not restrict.

Other Factors That Affect Weight Loss

It's also important to take into account the many chemical and biological processes that affect weight loss. Here are three factors that could determine how well calorie cycling works.

Leptin . Leptin is a hormone that signals to the brain that you've eaten enough food. If you eat a larger meal than usual, your body increases its production of leptin for up to 24 hours. That means that you may feel satisfied longer. If you're doing calorie cycling, the leptin produced on your higher calorie days may keep you satisfied the next day. 

Exercise and Resting Metabolic Rate. Exercise could be more important than diet in determining your metabolic rate. When you exercise, you not only burn calories while you're working out, you also burn more when you're resting.

About 60% to 75% of the calories you burn each day happens when you're resting. So, boosting your resting metabolism can significantly impact the total amount of calories you burn.

Dopamine . After a good meal, your body releases the pleasure chemical known as dopamine. When you don't consume enough calories, you may find that you crave more food as your body seeks that pleasurable feeling. Exercise also releases dopamine, so being active could help you feel satisfied with a lower calorie meal. 

The bottom line is that restricting calories doesn't always result in long-lasting weight loss. Calorie cycling or calorie shifting might be better than simply reducing calories, but the evidence isn't strong.

Instead, health experts recommend choosing nutritious foods, practicing portion control, and developing an exercise habit

WebMD Medical Reference Reviewed by Dan Brennan, MD on May 03, 2021

Sources

SOURCES:

Diabetes: "Is the Energy Homeostasis System Inherently Biased Toward Weight Gain?"

Harvard Health Publishing: "Exercise and weight loss: the importance of resting energy expenditure." 

International Journal of Preventive Medicine: "Calorie Shifting Diet Versus Calorie Restriction Diet: A Comparative Clinical Trial Study."

Journal of the International Society of Sports Nutrition: "Effects of diet cycling on weight loss, fat loss and resting energy expenditure in women." 

National Institute on Aging: "Calorie Restriction and Fasting Diets: What Do We Know?" 

Northwestern Medicine: "The Skinny on Cheat Days." 

Obesity: "Persistent metabolic adaptation 6 years after “The Biggest Loser” competition." 

TuftsNow: "Why It's So Hard to Diet." 

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