Here’s the continuation of the article "Energy Metabolism," where we explore the question of how much energy you actually need per day.
This is not only interesting for those aiming to lose weight. Often, people underestimate how much energy they really need and, conversely, overestimate how much energy they actually burn during sports or physically strenuous work.
The physiological calorific value is the amount of energy in kJ (kilojoules) released in the body when 1 gram of the respective nutrient is burned (1 kilocalorie = approx. 4.19 kJ).
- Carbohydrates: 17.2 kJ (4.1 kcal)
- Proteins: 17.2 kJ (4.1 kcal)
- Fats: 38.9 kJ (9.3 kcal)
One kilocalorie is the amount of energy needed to heat 1 liter of water from 14.5 to 15.5 degrees Celsius.
The daily energy requirement depends on age, gender, and the type of physical activity. It consists of the basal metabolic rate, activity metabolic rate, digestion loss, and the specific dynamic action of nutrients. Schematically, this can be represented as follows:
Example: With a body weight of 60 kg and medium to heavy physical work, the daily energy requirement is about 3000 kcal.
After food intake, the metabolic rate increases due to metabolic processes. This effect lasts for about 6-18 hours and is referred to as the specific dynamic action of the macronutrients fats, carbohydrates, and proteins.
Each macronutrient not only provides energy to the body but also requires energy: digestion, absorption, storage, breakdown, transformation, and transport processes all require energy.
The metabolic increase, however, is not the same for each macronutrient:
- Fats: 2-4% of the basal metabolic rate.
- Carbohydrates: 4-7% of the basal metabolic rate.
- Proteins: 20-30% of the basal metabolic rate (highest increase in metabolic activity)
The basal metabolic rate or resting metabolic rate is the amount of energy your body requires at complete rest, after 12 hours of fasting, and at a neutral temperature (clothed at 20 degrees, unclothed at 30 degrees) for all metabolic functions. It consists of the maintenance energy for cell life processes (basal metabolism) and the energy production required for all autonomously regulated processes.
The basal metabolic rate can, for example, be determined using the respiratory quotient (ratio of CO2 excretion to O2 intake) via a respiratory gas analysis (e.g., aeroscan). For precise information, such a test is recommended. There are also basal metabolic rate formulas, though these provide only a rough estimate.
The activity metabolic rate refers to all movements or physical exertions that exceed the basal metabolic rate. These exertions lead to an increased energy expenditure.
The amount of activity metabolic rate depends on the mass of the muscles used as well as the intensity and duration of the muscle work.
And who would have guessed: During sports, the energy expenditure usually reaches higher values than during "normal" work.
Here are some examples (note: average values):
- Running 9 km/h = 10 kcal/min
- Running 15 km/h = 11.4 kcal/min
- Cycling 43 km/h = 15.7 kcal/min
- Swimming 20 m/min (breaststroke) = 4.5 kcal/min
- Swimming 50 m/min (breaststroke) = 11.3 kcal/min
- Handball: 19.3 kcal/min