WEIGHT MANAGEMENT ∙ 5 minutes read

What is a calorie deficit and how can I stick to it?

By Ashton Sheriff | Medically reviewed by Danielle Brightman

If you’ve been scouring the internet trying to find weight loss tips, you’ve no doubt been bombarded with influencers claiming they have the “best weight loss diet” or companies offering an overwhelming range of weight loss supplements.

Many of them claim they can help you lose weight fast and help you achieve your dream physique. While some of these influencers and companies are well-meaning, others take advantage of consumers’ ignorance to pedal weight loss “solutions” that are simply gimmicks.

So, where do you begin if you want to lose weight? If you want to lose weight and keep it off, the two best things you can do are (1) understand what a calorie deficit is, and (2) stay in a calorie deficit on a daily basis.

What are calories?

The amount of energy in an item of food or drink is measured in calories. The more calories a food has, the more energy it’s able to provide your body. 

In recent years, the word “calorie” has pretty much become synonymous with “weight gain” and “unhealthy food”. But calories aren’t inherently bad. They’re simply a measure of energy. 

Calories come from carbohydrates, fats, and proteins. Sources of each include:

  • Carbohydrates (sugar, pasta, bread).
  • Fats (fatty cuts of meat, dairy products, cakes).
  • Proteins (meat, nuts, eggs).

Once again, calories aren’t essentially evil. If you eat the right amount of calories your body needs to maintain itself then it’s unlikely that you will put on weight. However, if you eat more calories than your body needs then you will store all the excess energy as fat. 

Now that we’ve covered calories, let’s dive into what a calorie deficit is (and how you can stick to it to lose weight). 

What is a calorie deficit?

A calorie deficit occurs when you consume less calories than you burn. 

Why is this important? Because maintaining a calorie deficit is the key to losing weight. 

Whenever you eat food your body either uses the calories in the food for energy or stores them as fat. If you eat more calories than you burn (which is known as a “calorie surplus”), then your body will store these calories as fat and this will cause you to gain weight. 

But if you’re in a calorie deficit (i.e. you eat less calories than you burn), your body is forced to draw from your pre-existing fat reserves to get the energy it needs to function. This causes the total amount of fat in your body to decrease as it’s used to produce energy.

Now, that’s a lot of information to take in at once, so to summarise:

  • Being in a calorie deficit allows your body to convert fat to energy. This results in fat loss around the body because your fat becomes a source of fuel. Therefore, maintaining a calorie deficit is the most important element to control when trying to lose weight. 

How to stay in a calorie deficit

There are a few things you can do to maintain a calorie deficit:

  • Consume less high-calorie foods (i.e. cut down on foods that are full of sugar and fats). 
  • Keep active (either exercise more or engage in more physical activity).
  • Reduce portion sizes (this will help you consume less calories).

Managing your diet by reducing your intake of high-calorie foods and moderating portion sizes is a great place to start if you want to stay in a calorie deficit. 

To compliment your dietary efforts, you should also incorporate some exercise into your weekly routine. You’ll find it easier to stay in a calorie deficit if you exercise, because exercise burns calories. Remember, weight loss is all about burning more calories than you consume. The more you exercise, the more calories you’ll burn - without needing to restrict your diet to something that leaves you feeling repressed. 

How to calculate calorie deficit

It’s all well and good knowing how to stay in a calorie deficit, but how do you know if you’re really sticking to it? Here’s a brief summary of how to calculate your calorie deficit.

  1. Calculate your daily maintenance calorie intake. This is the number of calories you need to consume to remain the same weight. This depends on factors such as your height, sex, weight, and level of physical activity. The easiest way to estimate your maintenance calories is to use a maintenance calorie calculator (there are a variety of free ones available online). 

  1. Calculate how many calories you consume a day. You can then compare this figure with your daily maintenance calorie intake to understand how many calories you need to cut to maintain a calorie deficit. As long as you consume less calories than your maintenance, you will lose weight. 

To make this clearer, let’s use an example. Let’s assume you’ve calculated your maintenance calorie intake and it’s 2300 calories. That means that you need to consume 2300 calories a day to maintain your current weight. This is your maintenance. This is your benchmark. 

Now, let’s assume you’ve counted the calories you’ve eaten over the course of the day and discovered you’ve consumed 2000 calories. Congratulations! You’re in a calorie deficit because you’ve consumed less calories than your maintenance.

However, if you’ve found that you’ve eaten the same amount of calories as your maintenance (or more) then you can either:

  1. Exercise to burn off the excess calories.
  2. Reduce your portion sizes the next day to stay in a calorie deficit (make sure to keep them reduced from then on).
  3. Eat less high-calorie foods the next day (and from then on) to stay in a calorie deficit.
  4. Action all three of the points above. 

It’s that simple. It’s nowhere near as complicated as people make it out to be. The key to losing weight is to maintain a calorie deficit using the three points above. 

Once again, exercise helps hugely because it burns calories and makes it easier to stick to a calorie deficit. If you’re the kind of person who enjoys food (don’t we all?), then it’s doubly worth exercising more because it allows you to enjoy a tasty, healthy diet without feeling like you’re restricting yourself too much. 

The bottom line

Forget fad diets: maintaining a calorie deficit is the best way to lose weight. By consuming less calories than you burn, you cause your body to use the fat stored within it as fuel. This results in overall fat loss and allows you to lose weight. 

To work out if you’re in a calorie deficit, first calculate your daily maintenance calorie intake and then how many calories you consume a day (these can be calculated with calorie calculators online). Compare the two. If you find that you’ve consumed less calories than your maintenance, then you’re in a calorie deficit. If you consumed the same amount of calories as your maintenance (or more), you need to reduce your calorie intake and/or burn more calories with exercise. 

Once you’re in a calorie deficit, you can maintain it by doing regular exercise, avoiding high-calorie foods, and moderating portion sizes. The longer you stay in a calorie deficit, the more you will continue to lose weight. 

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