This article has been Fact-Checked by Kendall Kennedy MS, RD, RYT
Since excess calories get stored on your body it sounds logical that you have to be in a calorie deficit for weight loss. A calorie deficit sounds easy and simple at first. However, the more you learn the more you find out that it’s pretty complicated at the same time.
How does losing weight work
To know how losing weight works you need to know how gaining weight works.
Your body needs energy from day to day to do things like walking, digesting food, keeping your heart beating,… The way it gets this energy is by extracting it from food.
The energy in food is present in the 3 macronutrients: protein fat and carbohydrates. This energy in food is measured in calories.
You gain weight when you absorb more calories from food than you use. Your body stores this excess energy as body fat.
The way you get rid of this body fat again is by absorbing less calories from your food than you need for your daily activities. When this is the case your body starts using stored energy, glycogen and body fat, to make up for the deficit.
The amount of calories needed on top of the energy in the food you eat is called your calorie deficit. Ultimately everyone needs a calorie deficit in some way or another to burn body fat.
How to figure out your calorie deficit to lose weight
There are a few steps you need to go through to create a calorie deficit that helps you lose weight.
How many calories do you use a day?
Before you can know how many calories you can eat you need to know how many calories you actually use every day.
The human body is a very complicated machine. There are too many things going on to keep track of. Some of the processes going on will burn calories other don’t.
Luckily you can a rough estimate of how many calories per day you need to maintain weight by filling in the most important info into a formula. One of the more commonly used formulas for this is the “Mifflin – St Jeor Formula”.
Here is how you can calculate how many calories you need per day to maintain weight:
Imperial: (4.536 × weight in pounds) + (15.88 × height in inches) − (5 × age) + 5
Metric: 10 x weight (kg) + 6.25 x height (cm) – 5 x age (y) + 5
Imperial: (4.536 × weight in pounds) + (15.88 × height in inches) − (5 × age) − 161
Metric: 10 x weight (kg) + 6.25 x height (cm) – 5 x age (y) – 161
Keep in mind that this is an estimate. The only way to know for sure is implementing this calorie count and seeing what the results are like.
In theory you can also get a more accurate view with certain lab tests but this can be expensive.
A popular way to increase calorie burning
On top of the regular calorie burning you can increase your energy usage. The most common way to do this is by exercising.
Different exercises have a different impact on weight loss. In general you have the choice between cardio/HIIT and weight lifting workouts. Cardio and HIIT are better for burning more calories in the next 30 minutes. Weight lifting is the most time-efficient exercise for long term weight loss.
How big should your calorie deficit be?
Now you know the amount of calories you need to absorb from food to maintain weight. The next step is to figure out how big your calorie deficit should be. The answer is not just “as much as possible”.
Losing weight too fast can cause negative effects. You might lose a lot of muscle which would help you lose weight in the short term but not in the long term. Losing weight could also make you feel miserable, dizzy and hungry all day. It can also slow make you burn less calories in general.
On the other hand there is losing weight too slow. This is more of a mental thing. You want to see positive results from your actions as soon as possible.
In general a calorie deficit of around 500 calories a day healthy weight loss rate is considered to be a healthy weight loss rate. If you keep that up every day you would lose about one pound of body fat each week.
There are also minimum calorie intake recommendations. For women this is at least 1200 calories a day and for men a minimum of 1500 calories a day (1).
Seeing faster results?
You might lose more than one pound a week. This is certainly common earlier in your weight loss journey. If you have a lot of weight to lose you can generally have a bit more fat loss each week without a problem.
On the other hand you have to remember that weight loss is not always fat loss. When people start losing weight they often eat fewer foods high in salt and carbohydrates. Both of these ingredients can make you retain more water.
Once you eat less of those foods you will consequently see a drop in weight because you are losing water weight (and hopefully also because of some fat loss).
If you keep seeing big weight loss results you might want to talk about it with a doctor.
How much can you eat to stay in a calorie deficit?
By now you have the amount of calories you can absorb a day to lose weight. With that knowledge all you have to know is how much energy different foods contain.
Packaged foods usually have the amount of calories displayed on the nutrition label. For whole foods you might have to do a quick search on the internet or an app. Adding up all these numbers is also known as calorie counting.
Keep in mind that only paying attention to the calories in your food is not the way to go. You also need things like protein, fats, vitamins, minerals, and fiber. These things are not only important for your health but also for your short and long term weight loss.
On top of that not all calories are the same for weight loss. Different habits can make you burn more calories. And so on. How you can create a calorie deficit that helps you lose weight is easier to explain with the above examples but it’s not the whole weight loss story.
You now have the theoretical amount of calories you have to eat for a calorie deficit and the theoretical foods can eat.
The next step is to test out these theories.
You need to keep your food intake and activity levels about the same while measuring your progress along the way. That way you can be sure whether or not the estimations are correct.
The duration of this testing period should be about 3 weeks to be able to make any conclusions. The more you measure the better you can see if it’s a fluctuation or a trend.
Different ways to measure your calorie deficit progress
You can measure progress towards your fat loss goals in many ways. Here is a short explanation of the advantages and disadvantages of the most common methods.
Weight on the scale
This is the most popular measuring method. The name “weight loss” implies that this is the only important thing but what you actually want is fat loss.
The main advantage of weighing yourself is that it’s easy to do. All that’s needed is 5 seconds on the scale.
The downside is that your weight is sensitive to fluctuations that have nothing to do with fat loss or gain. This is easy to understand with a little experiment:
Weigh yourself. Step off the scale and drink a liter of water. Step on the scale again. Voila you now weigh one kilogram more without gaining fat. And water intake isn’t the only thing that causes these fluctuations.
If weighing is your main way of measuring progress you need to keep in mind that there will be big fluctuations. Try to not put too much value on individual measurements but trends instead.
Body fat percentage
The next measurement method is tracking body fat percentage. This is is how much of your body weight is due to fat. So let’s say you weigh 100 and 20 of that is fat. Then your body fat percentage is 20%.
If you can track body fat percentage accurately it’s the best way to measure progress. The problem is that measuring it is or expensive or inaccurate or requires skill to do accurately.
Last but not least is circumference. You can measure with any regular measuring tape the circumference of body parts like legs, arms, belly and thighs.
The advantage is that circumference is easy to measure and also a fairly accurate way to determine progress.
The downside is that you can feel like you’re not making that much progress. One pound of body fat overall will most likely not come down to too much reduction in circumference.
What if you’re in a “calorie deficit” but not losing weight?
The first possibility is that you’re losing fat but not losing weight. In this case you are probably doing a good job. Weight loss will soon follow.
The other option is that you’re not actually in a calorie deficit. By definition a calorie deficit means you’re doing enough to lose weight. It means that you have to use stored energy to keep doing what you’re doing.
Keep in mind that the formulas for the previous steps are just estimations. The actual amounts of calories used and calories absorbed from food vary a lot from person to person.
The next step is to take another look at your daily habits involved with your health for room for improvement.
Things to keep in mind
On top of the previous things you need to keep a few things in mind when thinking about a calorie deficit for weight loss.
Your calorie deficit won’t last
A common situation is that someone loses some weight. They keep eating and doing the exact same things but after a while they stop losing weight. They hit a weight loss plateau.
Remember that weight was one of the factors in the formula to calculate how many calories you burn each day. Once you lose weight you will burn less calories.
Losing weight also often involves losing muscle and changes in certain hormone levels. Both things that can reduce the amount of energy you use.
The solution is to increase the amount of energy you use or absorb less energy. When you make your changes it’s back to using these new habits for a few weeks and measuring progress.
Different ways to achieve a calorie deficit
Often people think that the only way to achieve a calorie deficit is to eat less calories or exercise more. This is not the case and often those are the most uncomfortable methods someone can use.
Permanent weight loss is about permanent habits
Too often people see losing weight as a temporary thing they do for a while.
This attitude can certainly help you lose weight but once you go back to your old habits you will regain the weight. Most likely a bit more because weight loss often results in a slower metabolism.
That’s one of the reasons why achieving a calorie deficit with crazy methods is not something that results in long term weight loss.
How important is a calorie deficit for weight loss?
By definition it’s essential. Just keep in mind that eating less and exercising more are not the only ways to achieve a calorie deficit. Otherwise your weight loss journey will not be fun and the weight loss will probably not last for long.