Caloric Deficit: What is it and How to Achieve it?

If you've taken any interest in nutrition or are looking to lose body fat, you've probably heard that a calorie deficit is necessary to do so. But what exactly does it mean and why is it so closely linked to fat loss? Does it really work or is it just one more of the many myths that exist in this industry?

Good news: a calorie deficit works for fat loss. In fact, this isn't a new concept or a fad diet but refers to consuming less energy than an individual's specific requirements. In this article, we'll dive into what it is and how to use it effectively and healthily.

Remember that you can use the Fitia app to perform a caloric deficit in a proper way and following the steps that we will explain below. Download it for free here .

What is Caloric Deficit?

Caloric deficit, also known as energy deficit, refers to consuming fewer calories than one expends (or expending more than we consume).

With this, our body turns to its own energy reserves to cover the "deficit" we've created. To do this, our body oxidizes fat stores and releases energy to maintain energy balance (according to the first law of thermodynamics). Thanks to this process and the oxidation of our fat reserves, our weight decreases.

To better understand this concept, it is necessary to understand that in order to function properly, the human body uses a certain amount of energy on a daily basis. This concept is known as caloric or energy expenditure. This expenditure of calories occurs through three components (1,2):

• Basal metabolic rate: This refers to the energy expenditure necessary for the basic functions required for human survival, such as breathing, circulation, organ functions, etc. This component accounts for between 60 and 75% of total caloric expenditure.
• The Thermic Effect of Food (TEF): Processing food also requires a small amount of energy, as it necessitates activating the functions of the digestive tract to, for example, break down food into nutrients and absorb them. Therefore, approximately 10% of the calories used in a day correspond to these functions.
• Physical Activity Thermogenesis: This component is divided into two groups that together represent between 15 and 40% of the total caloric expenditure.
  • Exercise Thermogenesis: The energy expended during planned exercise or sports activities.
  • Non-Exercise Activity Thermogenesis (NEAT): The energy expended from physical activity that is not related to planned exercise or sports, meaning the movements one makes on a daily basis like walking, cleaning, cooking, among others.

The following infographic will help you visualize it better:

Therefore, the sum of all these components results in the energy that each individual expends in a day.

Then, if the foods we consume throughout the day provide us with a number of calories equal to what we expend, we would be consuming what is called "maintenance calories" because we achieve an energy balance. This will cause us to maintain a stable weight over time. Neither increasing nor decreasing.

On the contrary, when the food consumed in a day provides less calories in total than we expend, we achieve an energy deficit. This, as a consequence, will cause the body to start drawing on reserves (especially fats) as a source of energy. However, it is important to emphasize that it is necessary to do so using the right tools to avoid negative consequences such as muscle mass degradation.

How to Calculate How Many Calories I Spend Per Day?

As we have seen before, in order to reach a caloric deficit it is necessary that we first know how much energy we use. It is important to emphasize that the total energy expenditure of each individual is different because it depends on characteristics such as sex, age, size and level of physical activity, etc.

There are several methods to calculate the energy requirement, being indirect calorimetry the most accurate so far (3,4). However, it is a difficult technique to access, as it is usually only available in specialized medical or academic settings (4).

For this reason, several equations have been developed to help predict the energy requirement. The most classic and widely used is the Harris-Benedict equation, which predicts the basal energy expenditure and, therefore, it is necessary to add a physical activity factor to obtain the total energy expenditure (4):

Harris-Benedict equation (revised by Mifflin and St Jeor):

Basal metabolic rate (BMR) males

BMR = (10 * weight) + (6.25 * height) - (5 * age) + 5

Basal metabolic rate (BMR) females

BMR = (10 * weight) + (6.25 * height) - (5 * age) - 161

Where:

• Weight is expressed in kilograms (kg).
• Height is expressed in centimeters (cm).
• Age is expressed in years.

Then, to calculate the total daily energy expenditure (TDEE), it will be necessary to multiply this BMR by an activity factor. There are estimates to obtain this physical activity factor depending on the lifestyle you lead; however, these may vary.

TDEE = BMR * Activity Factor

This table can serve as a reference for estimating the physical activity factor:

Table adapted from Human Energy Requirements, FAO/WHO/UNU (5).

As well as this one, there are other equations to estimate the energy requirement such as the Mifflin equation, Schofield, WHO/FAO and even some that have recently been validated (6). It is therefore important to understand that any form of calculation represents an estimate but not an exact value. For this reason, it is advisable to work with ranges rather than fixed numbers.

Also, you can easily calculate your requirement using the Fitia app. We use an adaptation of Harris Benedict's formula which is more accurate. Download it for free here .

How to calculate the caloric deficit?

Once you have found the maintenance energy requirement (TDEE), you proceed to make an adjustment towards a deficit. However, this should be done with caution, as it has been seen that making very severe energy deficits could cause unwanted loss of muscle mass, higher incidence of injuries, hormonal dysregulation, amenorrhea (absence of menstruation) in the case of women, excessive fatigue, nutrient deficiencies, poor athletic performance, among others (7,8).

In this sense, to achieve optimal fat loss, an energy deficit of about 500 kcal below the maintenance level (9) or a deficit of 20-25% of maintenance calories is recommended. For example, if your maintenance calories (or TDEE) are 2,500 kcal, an appropriate caloric deficit might be 2,000 kcal. The evidence seems to suggest that maintaining this range of decrease would not incur negative consequences or involve very extreme changes that cannot be maintained over time.

Some people choose to keep the energy deficit constant during the week and others choose to do so intermittently (e.g., on weekends consume your maintenance calorie level). Studies to date show that there are no significant differences in weight loss, fat mass, and biochemical parameters such as glucose and insulin levels when comparing these two strategies of intermittent versus continuous deficit over time (10). It should be emphasized that the weekly energy deficit of both scenarios has to be the same to achieve similar results. In this sense, the recommendation is to resort to the way that generates more adherence in the person, since in this way it is guaranteed that the process is maintained for a longer time. In fact, it has been seen that a flexible approach to diet has better results in fat loss than very strict control (11).

Two complementary ways to achieve a deficit

• Reducing energy intake: Foods provide energy, and it's precisely the energy balance that we aim to modify when creating a deficit. Thus, one of the most evident strategies is to reduce the energy intake that comes from food.
• Increase the level of physical activity: As seen, the energy requirement depends to some extent on the level of physical activity of each individual. Therefore, increasing the level of activity will increase the total energy expenditure, which could create an energy deficit even if caloric intake is not modified. However, if this method were to rely solely on exercise, it could prove ineffective since, as can be seen in the previous graph, exercise thermogenesis represents only up to 10% of the total energy expenditure. On the other hand, increasing NEAT, that is, the thermogenesis of movement outside of exercise, appears to be a more effective strategy that can be combined with a reduction in food intake. Remember that a person who sits all day and trains for 1 hour a day is not considered active, but rather as a sedentary person who trains.

Tips for a calorie deficit

• Consume foods with low calorie density, meaning foods that provide few calories in a large volume or quantity. This will help generate more satiety and prevent hunger. Within this group, you can find vegetables, fruits, legumes, tubers, fish, and lean meats.
• Increase your protein intake. Proteins are the macronutrient that best controls appetite. Moreover, it has been shown that an adequate intake (between 1.2 and 2.2 g/kg/day for physically active individuals) will help maintain the amount of muscle mass we have, especially during a caloric deficit. 
• Strength train at least 3 times per week. This will help retain maximum muscle mass in stages of caloric deficit. Even, in beginner subjects, muscle mass gain while losing body fat is frequently observed through a slight caloric deficit (5-15% deficit) or by consuming the same amount of maintenance calories.
• Increase your fiber intake. Fiber delays gastric emptying, i.e., it causes food to stay in the digestive tract longer. This will make the compounds responsible for producing hunger signals take longer to be released, as they are highly dependent on gastric contents (if the stomach is still full, these signals will not be produced).
• Avoid liquid calories. Liquids do not generate a feeling of satiety or delay gastric emptying in the same way that solid foods do. On the contrary, they are absorbed very quickly. Products such as sodas, fruit juices or alcohol are not our best allies in stages of caloric deficit.
• Get enough rest. A rest of at least 7 hours a day is necessary to regulate the hormones that control appetite and satiety. Also, better quality sleep is related to greater body fat loss.
• Increase your daily physical activity level (or NEAT) with simple habits such as:
  • Getting around by walking or biking.
  • Use the stairs and avoid elevators
  • Keeping your house tidy
  • Parking away from work (to force yourself to walk)
  • Walking while talking on the phone (with caution)
  • Take breaks that involve walking