Very few people are really aware of how many or, depending on the situation, how few kilocalories we burn every day and how much energy we need in the form of food. Although exercise is an essential factor for effective weight control, it is often overestimated in terms of calorie consumption.
Burning and feasting in balance.
How to calculate your energy expenditure.
Our body is an engine that needs to be regularly fed with energy to keep it working. Carbohydrates, fats and proteins – the body converts these food components into glucose, fatty acids and amino acids and thus fuels the organs. The amount of calories needed to maintain basic vital functions is called the basal metabolic rate. If you have a high basal metabolic rate, you are one of the lucky people who can eat without worrying about gaining weight. Because the higher the basal metabolic rate of a person is, the better he utilizes the energies from food. People with a high basal metabolic rate are therefore less likely to have problems with obesity than people with a low basal metabolic rate.
Modest basal metabolic rate
If we lounged on the sofa all day, the basal metabolic rate of an adult would be between 1,300 and 1,800 kilocalories, depending on how heavy and old he or she is. This is roughly equivalent to the amount of energy contained in two schnitzels with French fries. The liver, kidneys, heart and skeletal muscles consume most of the calories. Alone.
Liver and muscles together require more than 50 percent of supplied energy at rest. But also the brain devours 18 percent of the basal metabolic rate every day, which corresponds to the energy of two bananas.
The average basal metabolic rate can be roughly determined using the "HarrisBenedict formula", which reads:
- Men: Basal Metabolic Rate = 66.5 + (13.7x weight in kg) + (5x height in cm) – (6.8x age)
- Women: Basal Metabolic Rate = 655 + (9.6x weight in kg) + (1.8x height in cm) – (4.7x age)
According to this formula, a 50-year-old man who is 1.80 meters tall and weighs 80 kilograms has a basal metabolic rate of 1722 kilocalories per day. A 50-year-old woman weighing 1.60 meters and 60 kilograms has 1294 kilocalories. If this output were to remain the same, both of them would not be able to eat too much in order not to get into an energy surplus, i.e. not to eat too much energy.
If you want to know exactly, you can have your individual basal metabolic rate measured with the help of a calorimetric test by a specialist or in a sports medicine institute, because the Harris-Benedict formula hardly does justice to individual differences. For this you have to breathe into a mask when you are sober. The connected computer records the oxygen and carbon dioxide content in the breathing air for about a quarter of an hour and uses this to calculate the basal metabolic rate. The result of men and women usually differs significantly. There are also differences within the sexes. If two people are the same age, weight and sex, this does not mean that their basal metabolic rate is identical, because the basal metabolic rate is not a fixed value. It depends not only on height, gender, weight and age, but also on the proportion of muscle and fat in the body. And temperature and air pressure, stress hormones and thyroid gland as well as genetic factors also influence the basal metabolic rate.
1. Weight and body size
In absolute terms, large and heavy people have a higher basal metabolic rate than small, light people. This makes sense, because they have to supply more mass and their organs are bigger. So more energy is needed to regulate the body’s functions. In relative terms, i.e. in relation to body weight, smaller people have a higher basal metabolic rate because they have a larger body surface area and therefore require more energy to generate heat.
Men have a higher basal metabolic rate than women because of their larger muscle mass.
The basal metabolic rate of young people is somewhat higher than that of older people. As muscle mass decreases with age and the metabolism slows down, the basal metabolic rate drops from the age of 30 onwards. I would have liked to have traveled more, but I didn’t. So a 50-year-old uses less energy at rest than a 20-year-old, even if both are the same weight and size. Therefore, in the long run, to prevent us from gaining weight as we age, we must either change our eating habits, exercise more – or build new muscle.
4. Body composition
Muscles are a sure guarantee for a high basal metabolic rate, because muscle tissue has a more intensive metabolism than fat: each kilogram of muscle mass burns about 60kcal more energy per day than a kilogram of body fat. Calculated over a month, this corresponds to 1800kcal, over a year even 21600kcal! Strength training can therefore increase the basal metabolic rate. The body converts fat into muscle and builds additional muscle mass in the process. These burn more calories – even at rest.
Fortunately, the basal metabolic rate is not all that concerns our energy balance. Also, for every step we take, the body has to fire the muscles with glucose – and that consumes extra calories. Even the biggest slackers don’t lie quietly on the sofa all day long. We all get up at some point, wash up, get dressed and go to work. This results in an individual "activity factor" for each person, also known as PAL value (Physical Activity Level, cf. Box S. 53) called. When standing, we consume about twice as many calories as when sitting, because the trunk and leg muscles have to keep the body in balance. In general, the more and the more frequently the muscles are used in daily work, the higher the calorie consumption.
Doubling and more
In the everyday life moved humans with a PAL value of 2 or higher can double their basic metabolic rate per day thus or with sport even more increase, because during the sporty exertion the energy consumption increases again substantially. The multiplication factor compared to the basal metabolic rate per hour can vary from 4 (very moderate exercise) to 12 (very strenuous activity) and in elite sports can even increase to a factor of 20.
Exactly how much energy is converted during athletic exertion depends on numerous factors; these include load intensity and volume; body weight, training condition and economy of movement, climatic conditions and, last but not least, the terrain profile (cf. Box right). It is therefore almost impossible to assign a specific calorie consumption to a sport across the board.
In general, however, it can be said that sports such as running, cross-country skiing, swimming and rowing, in which large muscle groups are in continuous use, burn a higher amount of energy than in the same time, for example, table tennis, technical disciplines in athletics or volleyball.
Sports and nutrition combined
What is crucial for successful weight control: every step you take consumes calories. And who burns more calories than he takes in, can reduce your weight. The best way to lose weight, or at least keep it off, is therefore a mix of lots of exercise and healthy eating, where you know (and ideally log for a while) how many kilocalories you burn and how many you eat. As long as the input is not greater than the output, you have nothing to fear.
If you are happy with your weight, you can treat yourself to something on days when you exercise – like a piece of cake, two scoops of ice cream or a small bowl of chips. After all, you burned more calories through exercise.
But don’t make the mistake of calculating your output too generously, because unfortunately it is often smaller overall than you think. Or you downplay the input. Snacking on a bar of chocolate as a reward for an endurance run of half an hour would therefore be too much of a good thing. Because with half an hour of walking you consume about 300 kilocalories. But a bar of chocolate has 550 kilocalories, almost twice as many.
Text by FITforLIFE- this blog post was provided to us by the Swiss magazine FIT for LIFE. Do you want to read regularly informative knowledge articles in the field of running and endurance sports, then click here.