How to Calculate and Set Your Calorie Deficit?

• A calorie deficit is a common feature of all weight loss diets, but their success depends on setting it up correctly.
• To maintain a lower weight in the long term, it is advisable to increase the level of daily physical activity.
• However, too large a calorie deficit can cause weight gain again and lead to health complications.

What is a calorie deficit?

You may have come across the statement that a calorie deficit is the basis for effective weight loss. But what does this term actually mean? And even better – how do you put this theoretical knowledge into practice?

Like all living systems, humans need energy to meet their vital needs. The exclusive source of this energy is the diet, through which the intake of nutrients and other substances that ensure the structure of body tissues and the smooth running of metabolic reactions is ensured.

Energy intake

The amount of food eaten can be simplistically described as energy intake. To determine this, it is necessary to keep track of the type and quantity of food and sweetened beverages consumed. In short, everything that contains energy must be counted.

Energy expenditure

On the other hand, energy expenditure encompasses the following areas:

• Basal metabolism: The amount of energy necessary to meet the basic needs of life (accounting for about 60% of total energy expenditure for an average person)
• Thermal effect of food: The energy needed to process the nutrients ingested, making up about 10% of total energy expenditure)
• Physical activity: This can be divided into habitual activities (normal daily activities such as walking and cleaning) and intentional activities like sports training. For an average person, physical activity accounts for about 30% of total energy expenditure, but for top athletes, it can account for more than 50%

Energy balance

Energy balance informs you about the ratio of energy expenditure to intake. The possible states of energy balance are:

1. Energy balance: The magnitude of energy intake and energy output is more or less equal, resulting in stable weight 
2. Positive energy balance: The magnitude of energy intake exceeds energy expenditure, leading to stable weight
3. Negative energy balance: The magnitude of energy expenditure exceeds energy intake from the diet, resulting in weight loss.

So what is a caloric deficit? It is the magnitude of the difference by which energy expenditure exceeds energy intake. For example, if you take in 2000 kcal per day and expend 2300 kcal, the 300 kcal difference is the calorie deficit.

How to set the calorie deficit correctly

Now you know what a calorie deficit is. However, the key to truly effective weight loss, which you will then be able to maintain, is to set it correctly. It doesn't matter whether your energy expenditure exceeds your dietary energy intake by 200 or 1,000 kcal; everything needs to be set precisely.

Ideal calorie deficit

An appropriate calorie deficit should be 15‑20% of your total energy intake. This means that if your maintenance intake (the amount of energy where the energy balance is balanced, i.e., energy intake and energy expenditure are equal) is 2300 kcal, your intake in a properly set calorie deficit for weight loss purposes should be 1840‑1995 kcal.

Too low calorie deficit

If the caloric deficit is less than the aforementioned 15%, weight loss might not be effective. The calculation of energy intake and expenditure can be the source of many errors that may affect the accuracy of the result and, thus, the correct setting of the caloric deficit. If you set a deficit of, for example, 5%, errors in the dietary record and calculations could result in the energy balance being more or less balanced, and the desired weight loss may not occur.

Too high calorie deficit

If, on the other hand, you set your calorie deficit too large, your weight loss would not be sustainable. You would likely face an energy deficit that can harm your physical health and mental well‑being in the long run.

How long does a calorie deficit last?

There is no definitive answer to this question, as it depends on your goal, initial weight, weight loss effectiveness and many other factors. However, weight loss should always be gradual, with the rate of weight loss being 0.5‑1% of body weight per week. For example, at 100kg, this would mean a maximum weight loss of 1kg per week. This rate helps ensure minimal loss of muscle mass and contributes to greater sustainability of weight loss.

To lose weight and maintain a lower weight, you need to think long‑term. Unfortunately, it doesn't work by eating differently for a few months and then going back to your old routine. If you really want to lose weight once and for all, you need to change lifestyle factors and eating habits. Therefore, it's important that your diet is sustainable over the long term during your weight loss efforts.

So, forget about fad diets or cutting out baked goods for the reasons mentioned above. This approach may get you quick results, but since you won't learn anything about a balanced diet during your journey, the results are unlikely to last. A much better strategy is gradual and sustainable weight loss that you can maintain long‑term without compromising your health. Once you reach your goal weight, you need to adjust your energy balance from negative to balanced to maintain your new weight.

Keeping weight loss on track

At first glance, it may seem like it doesn't matter whether you take in 1200 or 2200 calories a day as long as you stay within a 15‑20% calorie deficit. In practice, however, the situation is more complicated. The advantage will always go to the individual who consumes more energy because eating too little can decrease your energy turnover, which is likely to slow down your metabolic activity in the long run.

So how can you eat more during weight loss, avoid "slowing down" your metabolism and reduce weight more effectively? The answer is simple: increase your energy expenditure so that you can eat more even during weight loss. Movement is one of the biggest tools you can use to influence your weight loss efforts. Besides significantly increasing the amount of energy you expend, physical activity helps protect your muscles from catabolism (breakdown), firm your curves, boost your self‑esteem and make your weight loss journey more enjoyable thanks to the release of endorphins.

How to calculate the calorie deficit?

As mentioned above, to determine the correct size of the calorie deficit, you first need to calculate your total energy intake and expenditure. Here's how to proceed:

Energy expenditure

First, calculate your basal metabolic rate (BMR). You can use the Harris‑Benedict, Katch‑McArdle or Mifflin‑St. Jeor equations. For greater accuracy, you can average the results from these equations. The next step is to calculate the energy expended on movement and physical activity, which you can derive from the so‑called PAL tables (Physical Activity Level, see below). You simply multiply the BMR by the number from the table that corresponds to your PAL

Example: 1600 kcal (BMR) x 1.6 (PAL) = 2560 kcal

The above method of calculation is more suitable for the general population, as it provides fairly accurate results. For more active athletes, it is more appropriate to divide the energy expenditure intended for normal daily activities and work using the PAL tables. To the result, add the amount of energy expended on intentional physical activity, which can also be tracked using tables and calculators or read from a smartwatch.

Example: 1600 kcal (BMR) x 1.4 (PAL habitual activity) + 400 kcal (running 60 minutes) = 2640 kcal

The last step is to calculate 10% of the intermediate result, which corresponds to the thermal effect of the diet. After adding it, you get the complete value of the total energy expenditure.

Example: 10% of 2650 = 265 kcal => 2650 + 265 = 2915 kcal

Source: German Society for Nutrition (DGE)

Calorie deficit

You now know the value of your so‑called maintenance intake, which corresponds to your total energy expenditure. If your goal is weight reduction, you need to lower this value by 15‑20%. In this case, the final value of energy you should take in per day would be 2332‑2478 kcal.

Bottom line

A calorie deficit is key to successful weight loss, but it's important to set the right size and calculate your daily energy needs accurately. When trying to lose weight, don't forget that long‑term changes to your lifestyle and eating habits are necessary to maintain a lower weight; short‑term or restrictive diets won't ensure long‑term results.

A very important part of successful weight loss is getting enough exercise. This will help increase your daily energy expenditure while preventing muscle catabolism.