Energy Requirements At Rest And During Activity

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Energy Requirements At Rest And During Activity
Energy Requirements At Rest And During Activity
Video: Energy Requirements At Rest And During Activity
Video: Energy Considerations in Nutrition: BMR, RMR & Physical Activity – Nutrition | Lecturio 2023, February
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Energy requirements at rest and during activity

Even with complete rest in deep sleep, the body needs a considerable amount of energy for the vital basic functions and for maintaining normal body temperature. This amount of energy is known as resting or basal metabolic rate. The body consumes more energy during physical activity than at rest - this additional amount of energy is the so-called performance expenditure. The total daily energy consumption (= energy requirement) can be estimated from the basal metabolic rate and the power metabolic rate.

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  • The energy consumption at rest
  • Calculation of the basal metabolic rate
  • The energy consumption during activity

You can calculate an estimated value for your personal energy requirements using the Chamber of Labor's online calorie calculator.

Note Formulas that calculate the total daily energy requirement or the calorie consumption through exercise only result in estimated values, as do exercise tables for energy consumption.

The energy consumption at rest

The basal metabolic rate depends on the body composition - above all on the body's muscle mass - because muscle cells also consume energy at rest. Body fat, on the other hand, primarily serves as an energy store and has no energy requirement of its own. Around half of the basal metabolic rate from metabolism is consumed by the internal organs (e.g. lungs, intestines, heart, kidneys or liver), while the brain and the musculature of the musculoskeletal system each need around a quarter.

In women of normal weight, the basal metabolic rate is around ten percent lower than in men of normal weight. This is due to the lower average muscle mass or the higher body fat percentage of women.

Women have a muscle percentage of 30 to 35 percent and a body fat percentage of 20 to 30 percent of normal body weight.

Men have a muscle percentage of 40 to 45 percent and a body fat percentage of 10 to 20 percent of normal body weight.

Calculation of the basal metabolic rate

Examples of calculating the basal metabolic rate of people of normal weight:

  • Women: 0.9 kcal / kg body weight / hour (for example at 65 kg = 58.5 kcal / hour or 1,404 kcal / day)
  • Men: 1 kcal / kg body weight / hour (for example at 75 kg = 75 kcal / hour or 1,800 kcal / day)

Note For overweight people, it makes sense to calculate the basal metabolic rate from the estimated normal weight and not from the measured body weight for a more precise estimate. The following formula can be used as an approximation: Normal weight (kg) = height (cm) - 100. The reason: The actual body weight would result in an excessively high basal metabolic rate due to the high fat content.

The age of a person also influences the basal metabolic rate: The energy consumption initially increases during the growth phase. From the age of 30, on the other hand, the basal metabolic rate begins to decline in most people (every ten years by around three percent of the initial value at the age of 30), because age-related muscle mass decreases and body fat mass increases. However, the individual basal metabolic rate can be changed at any age through regular, targeted training.

The energy consumption during activity

As soon as the body becomes active and is no longer in a state of rest - for example when we walk, run, hold objects, lift something or do sports - it uses energy in addition to the basal metabolic rate. For this we need the skeletal muscles. These muscles are the largest organ system in humans and are responsible for a substantial part of the body's calorie consumption. The brain itself only consumes a little more energy when it is very active than when it is at rest. The nerve cells only use glucose.

Note A metabolic unit (MET) is the individual energy expenditure under resting conditions (basal metabolic rate). To compensate for the differences in energy expenditure due to gender and size differences in the same activities, the performance is given in MET. To do this, the energy expenditure during physical activity (= basal metabolic rate plus performance expenditure) is divided by the basal metabolic rate.

For example: Light physical work causes an energy expenditure of around 1.5 METs (basal metabolic rate plus 50 percent).

Examples of the approximate energy consumption of certain activities (based on a male person, 75 kg

  • Standing still: 90 kcal / hour or 1.2 METs
  • Office work: around 115 kcal / hour or 1.5 METs
  • Washing dishes: about 170 kcal / hour or 2.3 METs
  • Mow the lawn (with an electric mower): around 340 kcal / hour or 4.5 METs
  • Running (8 km / h): about 620 kcal / hour or 8.3 METs.

You can find more examples of the energy consumption of physical activities here.

Note After physical exertion, the energy expenditure does not immediately return to the starting level. The body also consumes more energy in the recovery phase - depending on how long and how intense the activity was.

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