When it comes to losing weight, deciding what meal plan to follow is half the battle. The rest of the fight? Hunger, cravings, and the resulting mood swings. Absent a miracle weight loss pill, the best hope we have is a diet that promises to avoid the aforementioned.
That’s the claim of metabolic confusion, a diet that alternates between periods of high and low calorie intake.
The diet purports to keep your metabolism humming and your satisfaction levels high—a theoretical combo that sounds like a recipe for success.
Does metabolic confusion work? And is it safe? We tap Imashi Fernando, MS, RD, to find out.
What Is Metabolic Confusion?
Metabolic confusion, also known as calorie shifting or calorie cycling, is the practice of alternating your calorie intake between higher and lower amounts. The goal is to trick your metabolism into staying high, where it burns more calories.
“Weight loss is about energy balance. A lower resting metabolic rate (RMR)—the number of calories your body burns at rest—would make it more challenging to promote continued weight loss,” Fernando says. Your body responds to long-term caloric restriction by slowing down your metabolism (1, 2, 3, 4). This unwelcome dip can lead to weight loss plateaus (and obvious frustration).
“Instead, the thought with metabolic confusion is that shifting between high-calorie and low calorie periods of eating will confuse your metabolism into maintaining your RMR,” says Fernando. “Effectively, avoiding the typical drop in RMR seen in other low-calorie diets.”
Does Metabolic Confusion Work?
“Maybe,” says Fernando. If it does work, she notes the scientific evidence is slim; just one study.
The study, published in the Journal of International Preventative Medicine, found that when compared to traditional calorie restriction (1,100 calories per day) calorie shifting (11 days of 1,100 calories, and 3 days unrestricted) was associated with more weight loss, less hunger, and greater diet adherence over 42 days (5).
What’s more, participants who shifted their calorie intake were able to maintain their pre-diet RMR, while calorie restriction led to a significant decrease in RMR.
However, another study—which followed participants for one year—found that there was no significant difference between calorie shifting and calorie restriction on weight loss and maintenance (6). A recent review agreed and cautioned against the unknown safety and metabolic health implications of calorie shifting—noting further research is needed (7).
There is more evidence that metabolic confusion works, but it suggests that the secret isn’t tied to metabolism. According to a review published in Obesity Review, since calorie shifting allows greater flexibility, breaks, and satisfaction it might be more sustainable than calorie restriction long term (8).
“If you struggle with sticking to caloric restriction, metabolic confusion may offer an alternative that allows you to take breaks from low-calorie eating while maintaining an overall slight caloric deficit long term,” says Fernando. “However, it is important to emphasize that the long-term effects on health are currently unknown.”
Is Metabolic Confusion Safe?
“As long as it’s not practiced in an extreme manner—for example, eating 800 calories for five days, followers by 3,500 calories for two days—it should be fine,” says Fernando.
Most research suggests the most sustainable, healthy weight loss programs rely on a nutritious diet and regular exercise to create a small caloric deficit of roughly 500 calories per day (9, 10). “If calorie shifting helps you get there, go for it,” says Fernando.
Although, there are a few red flags. “The biggest safety concern is not getting at least the minimum required daily amount of macro and micronutrients for age and biological sex, which is necessary for optimal functioning body processes,” she advises.
Plus, metabolic confusion may not be ideal for those with diabetes. “Calorie shifting could dramatically affect blood sugar levels, which could be dangerous for people with diabetes,” warns Fernando. “It’s important to review with your doctor, especially if you are taking any medications for blood sugar management.”
How to Do It
Determine your calories
With metabolic confusion, the focus is on how many calories you consume, not the foods you eat. While calorie amounts vary, many metabolic confusion plans suggest limiting calories to 1,200 on low calorie days, and around 2,000 on high calorie days. That’s… not much.
“Setting an arbitrary daily calorie goal ignores all the factors that go into determining individualized energy needs,” says Fernando. “This could severely under- or over-fuel your body, directly impeding weight loss results (11).” Rather, Fernando recommends a calculated, personalized approach.
Calorie needs shift with differences such as age, sex, body size, and activity level but most adults need a minimum of 2,000 calories per day—more if you exercise (12). “Plus, prolonged severe calorie restriction will make it more challenging to obtain all your macro and micronutrients in recommended amounts,” she warns. “Get it wrong and it could lead to malnutrition.”
She suggests working with a registered dietitian to get the calories (and macros and micros) right. “Indirect calorimetry is the gold standard for determining individual RMR and is what a registered dietitian (RD) will use to accurately determine your calorie needs,” says Fernando.
If working with an RD isn’t feasible, Fernando recommends at least using a calorie calculator to get a rough estimate of your needs.
Choose a format
You’ll then need to decide how often to switch between high- and low-calorie days. “The metabolic confusion diet does not provide any guidelines on the most effective format, and there’s very little research to suggest one schedule is more effective than another,” says Fernando.
The good news: this gives you the flexibility to choose what works best for you. Some plans switch every other week or month. Others (like Jimmy Kimmel) subscribe to an every few days format—similar to a 5:2 fasting schedule, where you eat normally for five days, then eat a significantly lower amount of calories for two days.
A big predictor of whether a diet is successful, per Fernando, is its long-term sustainability. That makes the flexibility of this eating pattern one of its biggest advantages.
Pros of Metabolic Confusion
Here, a few reasons to give metabolic confusion a shot.
More mindful eating
“Tracking calories can help you become more familiar with how many calories are in one serving of your favorite foods—prepare to be surprised,” says Fernando. “After a while, you’ll become a pro in estimating how many calories are on your plate without the need for measuring cups or a food scale.”
While understanding calories is an important step to making healthier food choices, Fernando points out that it’s not the only factor. Your macro and micronutrients matter, too (more on that below).
Since the metabolic confusion diet is designed to increase calories in an intentional manner, Fernando notes you may avoid the feelings of deprivation and consequent cheat days that come hand-in-hand with many other low-calorie diets (13, 14).
Still, “whether you are calorie cycling or not, eating high volumes of ultra-processed foods high in added sugar, salt, and saturated fats will leave you craving more,” says Fernando. “The easiest way to fight hunger cravings is to aim for balanced meals and snacks with an adequate amount of protein, fiber, and healthy fats.”
“We are social creatures, and food plays a role in many social settings,” says Fernando. “The flexibility of the metabolic confusion diet allows you to still enjoy a meal at a family gathering, Sunday brunch, or birthday party—while avoiding the feelings of failure that often come with trying to stick to other restrictive diets.”
One of the main benefits of the metabolic confusion diet is that it doesn’t eliminate specific nutrients or foods you might save for special occasions. Studies show that the more flexible a diet is, the more likely you are to follow it in the long run (9, 10).
Cons of Metabolic Confusion
While there are some benefits to metabolic confusion, there are some drawbacks to consider.
Metabolic confusion is more flexible and may lead to less cravings, but it’s still restrictive. “Prolonged caloric restriction can lead to a poorer quality of life,” says Fernando. “You may find you have lower energy levels or micronutrient deficiencies without overt symptoms. That’s why it’s so important to work with a trained healthcare professional who can help you monitor your nutrition.”
Besides being tough to follow, studies show most restrictive diets fail to produce long-term weight loss results (9, 10, 15, 16). They also suggest you’re better off making sustainable lifestyle changes like a modest calorie deficit through a nutritious diet, and exercise.
It Emphasizes Quantity Over Quality
The quality of your food matters. “A major downside to metabolic confusion is that it focuses on calories, regardless of where they come from,” explains Fernando. “An ultra-processed frozen dinner might be 300 calories whereas whole grain toast, two eggs, and half of an avocado is 350 calories. Less calories isn’t always the better choice.”
A diet high in ultra-processed foods puts you at a higher risk for early death (17). “Opt for lean protein like chicken, lean steak, and protein powder, healthy fats like olive oil, avocados, nuts, and seeds, whole grains, leafy greens, and fruits and vegetables,” she says.
“The best diet is an eating pattern that you are able to maintain through the rigors of daily life,” says Fernando. “If you can’t make it sustainable for you, it won’t be effective in the long run.” She encourages you to envision following a metabolic confusion diet every day for the rest of your life—is it feasible? If not, it’s not the diet for you.
How to Boost Metabolism
A reduced metabolic rate is a natural response to reduced calorie intake. Although this reduction is inevitable, there are a few ways to keep it moving.
The single most effective thing you can do to combat a drop in metabolism is strength training. Weight loss naturally reduces metabolic rate and muscle mass (18), but muscle burns more calories at rest than fat. To lose weight, you want as much muscle as possible.
Regular strength training can help you maintain and build muscle mass, and is associated with a higher RMR (19, 20). This means, whether you opt for bodyweight training or pick up a heavy set of dumbbells, you give your metabolism a helping hand.
Regardless of which diet you choose or the severity of calorie restriction, it’s important you get enough protein. “To maintain and build muscle, I recommend at least 0.7 to 0.8 grams of protein per pound of body weight for those who engage in regular strength training,” says Fernando. “If it’s impossible to fit this much protein within your daily calorie limit, chances are your limit is too low.”
Studies show protein can help reduce appetite and cravings while boosting metabolism (21, 22, 23). One study published in Nutrition and Metabolism suggests that despite restricting calories, a keto diet high in protein and fat didn’t induce the expected dip in RMR, which researchers suspect was due to the preservation of lean muscle mass (24).