Why Calorie Deficit Diets Don’t Work (and What Does Work)

The traditional weight loss advice to eat less and exercise more doesn’t work. If you’ve ever tried to lose weight, then you know this is true!

What actually happens is you lose a little weight at first but then the progress stops. No matter how strict you are or how much you exercise, the diet always fails. And often you gain back the weight you lost.

The truth is, it’s not as simple as eating less. Because your body is programmed to prevent you from losing weight in response to a calorie deficit.

But the good news is, there are practical steps you can take that will help you lose weight and keep it off. First, let me explain what a calorie deficit is and why it doesn’t work.

What is a Calorie Deficit?

A deficit is defined as a shortage. So a calorie deficit means you’re eating a shortage of calories. In other words, you provide your body with less energy than you expend in a day.

The amount of energy you expend in a day is called TDEE (total daily energy expenditure). And it includes the energy you burn through exercise and physical activity. But usually, 65-80% of your energy expenditure comes from your metabolism.

Related Article: Calculate Your TDEE

Your metabolism is the calories your body burns just keeping you alive. Furthermore, your metabolic rate changes in response to a number of factors including how many calories you eat.

Put simply, a calorie deficit is an energy shortage. Which is why calorie deficit diets don’t work in the long run.

4 Reasons Why Calorie Deficit Diets Fail

At the start of a calorie deficit diet, you always lose weight. But the problem is the weight you lose is more than just body fat. In fact, a good portion is lean mass (aka muscle).

Reason 1: You Lose Muscle

There are a couple of reasons why you lose muscle on a calorie deficit diet.

First, when you cut calories you usually eat less protein. So there are fewer amino acids to build up muscles as they break down. That’s called a negative protein balance, and it results in muscle loss.

Second, muscle takes energy to maintain while fat stores energy. Therefore, your body eliminates muscle tissue when calories are restricted in order to conserve energy.

To illustrate, researchers from Stanford University put active men on a 40% calorie deficit diet1. Then their body composition was tracked over the course of 3 weeks. Including total weight, lean mass, and body fat.

calorie deficit change in body mass

Adapted from Friedlander, et al.

As a result, participants lost an average of 8.4 pounds in just 21 days. Sounds great, right? Well, in this case, over half of the weight loss was lean mass. And that has not so great consequences.

Reason 2: Your Metabolism Slows Down

By getting rid of lean mass your metabolism slows down. To put it another way, your body reduces how much energy you need to survive.

Like tossing gold out your car window to get better gas mileage. You go further on less fuel, but you lose a valuable resource.

In the previous study, researchers also tracked the participant’s metabolic rate over the 3-week diet. As a result of the calorie deficit, metabolism dropped by as much as 230 calories.

calorie deficit change in metabolic rate

Adapted from Friedlander, et al.

Furthermore, smaller calorie deficits also result in metabolism slowdown. A similar study reported metabolism decreases of 100 cal/day after 19 days of a 20% calorie deficit2.

Admittedly, 100 cal/day doesn’t sound like much. But over the course of 3 weeks, that’s enough energy to burn an additional 0.5 lbs of fat.

The point is, your body adjusts to the calorie deficit in order to conserve energy.

Reason 3: You Stop Losing Weight

As a result of your body’s ability to adapt, you eventually hit a plateau where you stop losing weight.

As an example, let’s say your TDEE is 2,500 calories per day. In other words, you eat 2,500 calories per day to maintain your weight.

Then you decide you want to lose weight. So you cut calories by 20% and eat 2,000 calories per day. At first you steadily lose weight. But after a while you hit a plateau.

In order to continue losing weight, you decide to cut calories another 20% to 1,600 calories per day. For a short period, the weight loss continues.

However, eventually you hit another plateau. Frustrated and hungry you finally give up and go back to eating 2,500 calories per day. Sound familiar?

Don’t feel bad. We’ve all been down this road and given up on diets. Unfortunately, the calorie deficit diet often leads to rapid weight regain.

calorie deficit graph

Reason 4: You Regain the Weight… And Then Some!

After the calorie deficit diet, your energy expenditure stays at a lower level. As a result, you regain a lot of weight (that scary red bar).

In many cases, you regain more weight than you lost. And the majority of the weight gained is body fat!

Eventually, your metabolism slowly increases again. But the damage has already been done.

By now it should be clear that a prolonged calorie deficit isn’t the answer. So how do you continuously lose weight and keep it off?

A Calorie Deficit Diet That Works

The first thing to remember is that your goal should not be weight loss. Because focusing on total weight loss incentivizes the wrong behaviors. Like severe calorie restriction.

Instead, you should focus on fat loss and muscle preservation. With that in mind, what do you need to do to lose fat while maintaining muscle?

Small, Incremental Changes

Calorie restriction is a slippery slope. Yet a calorie deficit is necessary for fat loss. So it’s important to realize that the severity of muscle loss is likely proportional to the calorie deficit3.

To put it another way, the steeper the slope, the faster you slide. Therefore, you should use the smallest possible deficit that results in fat loss.

You can find your deficit by calculating your TDEE and subtracting 100 to 200 calories to get your daily target. Or, simply eat 100 to 200 calories less than you would to maintain your weight.

In addition, you should incrementally lower calories at a set frequency. Such as once per week, or every other week.

small incremental calorie deficit

Small, incremental adjustments ensure the slight calorie deficit remains and you continue to lose weight. But also prevent the unwanted side effects of the large calorie deficit.

The rate of fat loss will be slower, but you will have more long term success. So think of it not as a crash diet, but as an ongoing lifestyle change.

Eat Plenty of Protein

Protein needs increase as calories drop and body fat decreases4. Because even a small calorie deficit can cause a negative protein balance which results in muscle loss.

Therefore, the best defense against muscle loss is to eat adequate amounts of protein. That amount could range from 0.8 to 1.3 grams per pound of body weight daily. As you get leaner and your calories get lower you should aim for the higher end.

Periodic High Calorie Breaks

Periodic “refeeding” is when you temporarily increase your calorie intake slightly above your TDEE. That is, you eat more calories than you burn.

The goal is to counteract the negative metabolic effects of the calorie deficit. And there is evidence that periodic refeeds increase hormones like leptin5, which stimulate your metabolism. Essentially, you “trick” your body into thinking it’s not in a calorie deficit.

Typically, a refeed is a 24 hour period once per week. And you should target 200 to 300 calories above your TDEE.

Putting It All Together

Once you understand these basic concepts, losing fat and keeping it off is easy. However, applying all this information to your own diet can be tricky at first.

For that reason, Nutritioneering offers a personalized Fat Loss Meal Plan. In this plan, we take care of everything covered in this article for you. From calculating your TDEE and protein target to creating your small, incremental calorie deficit schedule.

In addition, you receive a template to help you create your daily meal plans in minutes. Along with workout routines and supplements to help you lose fat faster.

So click the button below to get your personal Fat Loss Meal Plan. Or click here to learn more.

Customize Your Fat Loss Plan

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