Calorie restriction is out, and the zig zag diet (aka calorie shifting, aka metabolic confusion diet) is in. Over the years, many have wondered why sticking to a restrictive diet with a set caloric goal can lead to weight gain or plateauing after just a few weeks.
As it turns out, when your body gets used to a set caloric intake, it starts to burn fewer calories overall. That means if you continue eating the same amount of calories each day, your body will eventually catch up, and you stop losing weight or even regain it.
This isn’t a modern-day phenomenon. It’s thought that when hunter-gatherers were faced with periods of starvation, their bodies would adapt in order to conserve energy and go into a sort of metabolic hibernation mode.
Enter the zig zag diet, which takes advantage of this theory. It makes you live exactly how the cavemen might have—eat less one day, feast the next. That means you’re constantly switching things up so your body never gets used to a set caloric intake.
Does this approach work? Let’s take a look.
As its name suggests, the zig zag diet is a way of eating that changes its calorie intake from day to day.
This means you could have a day where you eat around 2000 calories, followed by a day where you consume 1500–1800 calories, and then a third day where you eat up to 2500 calories.
The idea is that by constantly shifting your caloric intake, you might avoid some of the biological responses that lead to weight gain and plateauing. This approach is intended to keep your metabolism on its toes so it’s constantly burning calories efficiently.
On top of that, the zig zag diet also allows for some variety in your meals, which can make it easier to stay on track.
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Studies on the effectiveness of the zig zag diet are still limited, but the few that have been conducted suggest that it may be a viable option.
We should mention that study size, duration, and design can vary greatly from one paper to the next, making it hard to draw definite conclusions.
In one study, 1 week of high calorie eating, followed by 3 weeks of a restrictive, low-calorie diet followed by 2 weeks of higher-calorie refeeding resulted in fluctuations in resting energy expenditure (REE). REE increased slightly during the initial overeating period, then decreased during the calorie restriction, then increased again during the refeeding period (14).
In another study, participants performed resistance training and were assigned to one of 2 diets: continuous energy restriction or intermittent energy restriction (5 days of restriction alternated with 2 days of elevated carbohydrate intake)(9).
At the end of the 7-week study, the participants in the intermittent group had better preserved fat free mass and slightly higher resting metabolic rates than the continuous restriction group (9)
However, some studies haven’t found a significant difference in weight loss or metabolism between zig zag dieters and calorie-restricted dieters (8) (10). This could be due to several factors, but more and better designed research is needed in order to draw any meaningful conclusions.
More research is needed to understand the effects of a zig-zag diet. Until then, it’s hard to say definitively whether this approach is better than traditional dieting for weight loss.
That said, a look into the metabolic adaptations to calorie-restricted diets in general may provide more insight into the efficacy of a zig-zag diet.
When you restrict calories for an extended period, your body will eventually adapt in order to conserve energy. This is called metabolic adaptation (13). Some of the changes that happen when you’ve been on a low-calorie diet for a long time may include:
A systematic review and meta-analysis found some evidence that calorie restriction may affect testosterone levels in men, but that the effect depends on their BMI. The studies they were able to include were limited, but suggested that calorie restriction may increase testosterone levels in overweight and obese men, but decrease testosterone levels in normal weight men.
Sometimes referred to as “starvation mode”, this is when your body decreases its energy expenditure in response to a decrease in calorie intake (2).
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To further conserve energy, your body may reduce the amount of physical activity you do. You may find yourself feeling exhausted and lacking the motivation to exercise. You may simply move around less throughout the day without even realizing it.
Studies have linked severe calorie restriction to decreased levels of thyroid hormone, which may further slow your metabolism (20).
Leptin is a hormone produced by fat cells that helps regulate appetite (16). Studies have shown that calorie-restricted diets lead to decreased leptin levels, which can cause increased hunger (19).
Cortisol is the “stress hormone” and high levels can lead to increased fat storage, especially in the abdominal area. It’s also linked to increased cravings and decreased energy levels (18).
Ghrelin is the “hunger hormone” and calorie restriction can increase levels of this hormone, leading to increased hunger and cravings (1) (7).
These metabolic adaptations can have a significant impact on your ability to lose weight and keep it off.
Without the proper nutrients and support, it can be challenging to maintain a caloric deficit long-term. That’s why even when you lose some weight through calorie restriction it can often be hard to keep the weight off in the long run.
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When you alternate between calorie-restricted and refeed days, you’re providing your body with the energy it needs to stay active and maintain muscle.
Essentially, some people believe that you’re “tricking” your body into thinking it’s not in a calorie deficit, which they claim can prevent or reduce the metabolic adaptations associated with strict dieting.
They suggest that if you can maintain an overall caloric deficit while still providing your body with enough energy to function, then the metabolic adaptations associated with calorie-restricted diets may be avoided or reduced.
In reality, there is no scientific evidence for these claims. Like any diet, this may work for some people and not for others.
The zig-zag diet might be a way for some people to:
Diets like keto are often criticized for being difficult to stick with long-term due to their restrictive nature (3). A lifetime of eating this way is usually not sustainable.
The zig-zag diet allows you to maintain an overall caloric deficit without feeling overly restricted or deprived. As it doesn’t limit what you eat provided you stay in a deficit, it’s a much more sustainable approach for the long term.
When you’re on an overly restrictive diet, your body will often begin to break down muscle for energy (17). This can be prevented by providing your body with enough energy and nutrients to function properly.
The zig-zag may help you do this by maintaining a more modest overall deficit, allowing you to maintain muscle mass while still losing fat.
By alternating between calorie-restricted and refeed days, you might avoid the metabolic adaptations associated with strict dieting (4).
Theoretically, as your body never goes into an extended deficit, it might never have to slow its metabolism or rely on other adaptive strategies. This could keep you from hitting a weight-loss plateau and ensure you see steady and consistent results.
Like most diets, the zig-zag diet has its drawbacks.
The zig-zag diet does not emphasize food quality. As long as you stay in a deficit, you can eat whatever you want on your refeed days. This may encourage unhealthy eating habits and a lack of nutritional focus. Remember, there’s more to your overall health than just losing weight.
Due to the nature of this diet, you’re likely to experience some unwanted weight fluctuations. As you alternate between a deficit and refeed days, your weight may go up and down accordingly. This can be discouraging if you’re looking for consistent, long-term results.
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The zig-zag diet requires a lot of planning and organization.
You’ll need to make sure that you’re eating the proper amount of calories on your refeed days, and that you’re alternating between high-calorie and low-calorie days. This can be time-consuming and inconvenient, especially if you’re already busy with other commitments.
The zig-zag diet can make it difficult to differentiate between a refeed day and an unhealthy binge. You may be tempted to go overboard when it comes to your refeed days, leading to feelings of guilt and shame.
If you have a history of disordered eating, this diet may not be the best choice for you.
If you decide to try the zig-zag diet, here are some tips for getting started:
The first step is to determine how many calories you need per day. You can use a calorie calculator to do this.
Once you know your daily caloric needs, you can then decide how many calories to eat on each low calorie and refeed day. A sustainable deficit might be around 3500 calories per week, which you would distribute among your low calorie days (6).
Along with the calorie content of foods, consider their nutritional value (15). Aim to fill your diet with nutrient-dense foods like fruits, vegetables, lean proteins, and whole grains on both high and low-calorie days.
Spend some time planning and organizing your meals for the week. This will make it much easier to stay on track and limit unhealthy foods (12).
Don’t set rigid rules for yourself. If a day doesn’t go as planned, don’t beat yourself up. Just get back on track the next day and keep going.
The zig-zag diet can be an effective and sustainable way to lose weight. By alternating between calorie-restricted days and refeed days, you might prevent metabolic adaptations and maintain muscle mass while losing fat.
However, it’s important to remember that food quality matters and that the zig-zag diet may not be right for everyone. Before beginning this or any other diet, consult with your doctor to ensure it is safe and healthy for you.
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