Why Calorie Deficit Diets Don’t Work

And The Right Way to Use Calorie Balance for Weight Loss

If you’ve ever tried to lose weight, then you know it’s not as simple as eating less and exercising more.

In reality, you lose some weight at first. But no matter how hard you try, the progress always stops. And eventually you gain back the weight you lost.

The truth is, fat loss isn’t not as simple as calories in vs calories out. 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 to lose weight and keep it off.

In this article:

  • Calorie deficit explained

  • 4 reasons calorie deficit diets fail

  • How to do a calorie deficit right

  • Your free personal weight loss calorie target

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 eat less than you burn.

The amount of calories you burn in a day is called TDEE (total daily energy expenditure). Of course some calories get burned through physical activity. But you may be surprised that your metabolism burns 65-80% of the calories you use every day.

Try the New & Improved TDEE Calculator

Your metabolism is the energy required just keeping you alive. However, your metabolic rate changes in response to many 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 almost always lose weight. But 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 requires alot of energy to maintain. 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 weight, lean mass, and body fat were tracked for 3 weeks.

calorie deficit change in body mass

Adapted from Friedlander, et al.

As a result of the calorie deficit, participants lost an average of 8.4 pounds in 21 days. Sounds great, right?

Well, in this case, over half of the weight lost was lean mass. More importantly, muscle loss has a negative effect on metabolism.

Reason 2: Your Metabolism Slows Down

When you lose 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. And they found that metabolism dropped by as much as 230 calories.

calorie deficit change in metabolic rate

Adapted from Friedlander, et al.

It’s also important to realize that the calorie deficit doesn’t have to be as large as 40% to lose muscle. 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 and decreases metabolism 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.

For example, let’s say your TDEE is 2,500 calories per day. That means 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 (2,500 x 0.2 = 500, 2,500 – 500 = 2,000). At first you lose weight, but you eventually hit a plateau.

In order to continue losing weight, you decide to cut calories another 20% to 1,600 calories per day (2,000 x 0.2 = 400, 2,000 – 400 = 1,600). For a short period, the weight loss continues but then 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. When dieting is done wrong giving up is inevitable. Unfortunately, rebounding from a severe calorie deficit 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. So you’re now in a large calorie surpluss when you eat more food. And you regain a lot of weight (that scary red bar).

In many cases, you regain more weight than you lost. Even worse, 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 eat to lose weight and keep it off?

How to Eat to Lose Weight & Keep If Off

The first thing to remember is that simply losing weight shouldn’t be the goal. Because focusing on total weight loss incentivizes the wrong behaviors – like severe calorie restriction.

Instead, 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 eat 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 as an ongoing lifestyle change instead of a crash diet.

Eat Plenty of Protein

The amount of protein you need increases as calories drop and body fat decreases4. 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 could range from 0.8 to 1.5 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.

How to Use a Refeed Day to Lose Weight

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.

Your Personalized Fat Loss Plan

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 ideal calorie deficit. And everything is built around your schedule.

In addition, you can get customized recipes that fit your calorie and macro targets. So you don’t even have to count calories!

Click the button below to create your FREE plan.

Customize Your Fat Loss Plan

About the Author

Jeremy Fox  –  Founder of Nutritioneering, Engineer, CPT, Bodybuilder, Coach

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