Recent scientific studies indicate that the cause of the obesity epidemic in our world is not a lack of physical activity, but rather overeating and the consumption of excessive calories.
Regular sports activities and basic physical movements “burn” only 10-30% of the calories burned daily, while the majority is used to support internal metabolic functions (~70%) – these are the processes that keep the body alive.
Hence, the answer to the question of how many calories are needed per day to lose weight: the amount should support metabolic functions and not significantly exceed this value. How much exactly – see below.
Before we begin, it is important for you to understand the following: any formulas for calculating calories provide only a relative average estimate of the number of calories per day, as they do not take into account individual characteristics of the body.
Two people of the same weight, age, gender, and level of physical activity can consume the same amount of food, say 2500 kcal, yet one may gain weight while the other maintains or loses weight, simply because their internal processes occur differently.
This explains the division into different body types: ectomorphs, mesomorphs, and endomorphs.
One of the most common formulas for calculating calories is the Harris-Benedict formula.
With its help, you can calculate not only your individual basal metabolic rate but also the necessary number of calories per day.
The basal metabolic rate is the number of calories that the body uses to maintain its internal processes. The lion’s share of calories (~70%) that we use throughout the day is attributed to internal metabolism.
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The Harris-Benedict Formula for Calculating Daily Caloric Needs
This formula was first published in 1918 and was later revised and refined in 1984 and 1990.
According to it, to determine how many calories you personally need per day to maintain your current weight, you need to multiply your basal metabolic rate (BMR) by your level of physical activity.
What is the Basal Metabolic Rate and How to Calculate It
The basal metabolic rate is the number of calories needed just to maintain internal processes when a person is at rest. Every single cell in the body requires energy to function. As long as a cell is alive, it consumes energy. This is the law of life.
The speed of internal metabolism is determined based on gender, age, and weight. Men have more muscle mass, and muscle cells consume more energy. With age, the speed of internal processes slows down, while in youth it is very high as the body is growing. The more weight, the greater the number of cells – mini energy consumers – in the body. It’s quite simple.
In these three variables lies the main drawback of the formula mentioned above – individual characteristics are not taken into account.
So, the Harris-Benedict formula for calculating the basal metabolic rate is as follows (weight – in kilograms, height – in centimeters, age – in years):
| Formula for calculating basal metabolic rate |
|---|
| Basal metabolic rate for men = 66 + (13.7 * weight) + (5 * height) – (6.76 * age) |
| Basal metabolic rate for women = 655.1 + (9.6 * weight) + (1.9 * height) – (4.7 * age) |
For a 40-year-old woman weighing 68 kg and 170 cm tall, we get: 655.1 + (9.6 * 68) + (1.9 * 170) – (4.7 * 40) = 1273 kcal.
For a 40-year-old man weighing 80 kg and 180 cm tall, we get: 66 + (13.7 * 80) + (5 * 180) – (6.76 * 40) = 1790 kcal.
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Considering the level of physical activity
Now, to determine how many calories are needed per day, it is necessary to take into account the level of physical activity in the formula. The following coefficients are used for this:
- 1.2 sedentary lifestyle (low or no physical activity)
- 1.375 low activity (1-3 times a week of light intensity)
- 1.55 moderate activity (training 3-5 times a week of moderate intensity)
- 1.725 very active (heavy training 6-7 times a week)
- 1.9 super active (very heavy training or physical labor)
How to use these coefficients:
For example, if a woman works as a postwoman (walking all day), her activity level will be 1.9. A man working in an office and exercising several times a week has a moderate activity level of 1.55.
The complete formula for calculating how many calories are needed per day
Now let’s combine the formula for determining the basal metabolic rate and the activity level to determine the number of calories needed per day to maintain current weight:
| Formula for calculating the number of calories per day |
|---|
| Number of calories per day = Basal metabolic rate * Level of physical activity |
For a woman weighing 68 kg and with a moderate activity level:
1273 * 1.55 = 1973 kcal
For a man weighing 80 kg with a moderate level of activity:
1790 kcal * 1.55 = 2775 kcal
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How many calories do we burn throughout the day while doing everyday tasks
As seen above, the necessary amount of calories per day is largely determined by the level of physical activity. This is the basis for the recommendation to engage in sports to lose weight.
Sports are undoubtedly beneficial for weight loss, but not as much as is commonly believed.
A closer look at the formula reveals that average activity (coefficient 1.55) and its complete absence (coefficient 1.2) give a woman a difference in calorie count of only (1273 * 1.55) – (1273 * 1.2) = 445 kcal, i.e., less than one chocolate bar…
In addition to sports, performing any everyday tasks contributes to calorie burning. The specific number of calories burned is mainly determined by weight.
For example, below is a list of some everyday tasks and the number of calories a person weighing 70 kg burns while performing them for 30 minutes.
| How many calories does a person weighing 70 kg burn while performing everyday tasks for 30 minutes | |
|---|---|
| Working on a computer | 51 |
| Cooking | 93 |
| Gardening | 167 |
| Shopping | 130 |
| Light office work | 56 |
| Playing with children | 149 |
| Reading | 42 |
| Sleeping | 23 |
| Standing in line | 47 |
| Walking (speed 3.5 km/h) | 149 |
| Washing the car | 167 |
| Watching TV | 28 |
| Mowing the lawn | 167 |
Men and women use calories differently
Men and women use calories differently. From the formulas provided above for calculating the basal metabolic rate, it is evident that one of the coefficients in one of the terms is gender.
Men generally have a lower body fat percentage and greater muscle mass. To maintain muscle mass even at rest, more energy is required. This explains why men burn more calories than women.
How many calories do you need per day to lose weight?
All the math presented above is necessary to understand how many calories are needed per day to lose weight.
Let’s use a simplified model.
In order to lose 1 kg, you need to burn approximately 9000 kcal (the energy value of 1 g of fat is 9 kcal). This means that if you need 2500 kcal to maintain your current weight, you need to exercise more or eat less. By how much?
Experts recommend losing weight gradually, a maximum of 1 kg every one to two weeks. To lose 1 kg in two weeks (burning 9000 kcal over 14 days), you need to burn an extra 640 kcal each day. This can be done by exercising more or consuming fewer calories (creating a calorie deficit), or by combining both approaches.
The mechanics of the process are of course more complex, and recent scientific research indicates that the relationship between burned calories and the level of physical activity is not linear (i.e., the more you exercise, the fewer calories you burn/lose weight), but the overall picture is clear.
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Additional tips for those losing weight
The process of losing weight is certainly much more complicated than simply counting calories on a calculator.
While the whole world is fascinated by various fat burners and other easy ways to lose weight quickly without effort, common sense and doctors say that the best strategies include adjusting your diet to limit calorie intake and regular exercise.
Also, consider the following recommendations:
- keep a record of everything you eat throughout the day: this makes it easier to identify the cause of weight gain either on your own or with a specialist
- remove refined, man-made products that contain empty carbohydrates (candies, cookies, chips) from your diet (see What not to eat to lose weight?)
- buy low-calorie alternatives to your favorite products at the store: skim milk instead of whole or cream, Greek yogurt instead of sour cream, popcorn instead of chips, dried fruits instead of sweets, thin pizza instead of thick (we buy it for enjoyment, not quantity), ice cream made from frozen fruits instead of regular, etc.;
- learn to read product labels to understand what exactly and in what quantity you are consuming;
- serve food on a plate from a common bowl, container, or package to initially limit portion sizes;
- make all changes gradually and stay away from magical diets and pills that attract with loud promises of quick results without effort (see The harm of fat burners).
