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Nutrition & Energy Balance

Energy balance is the energy needed (cal/kJ) to maintain life or to perform certain activities. Energy balance is made up by the following:

  • Basal Metabolic Rate – the amount of energy needed to maintain life and to regulate body temperature at rest (homeostasis). This measurement is taken in the morning, after a relaxing sleep and before breakfast.
  • Thermic effect of exercise – daily activity energy consumption. It includes physical exercise but also daily activities such as walking, driving, dressing, housekeeping, etc.
  • Thermic effect of food – the amount of energy needed on top of resting metabolic rate, that results from the consumption, digestion, absorbtion, transport, metabolism and storage of consumed food within the body. This is normally 10% of total energy expenditure.

 

*AIPT – Certificate III in Fitness, Nutrition - Module 2

*Australian Institute of Personal Trainers – Certificate III in Fitness, Nutrition – Module 2

How to calculate energy expenditure (intake):

Basal Metabolic Rate (BMR) formula uses variables such as height, weight, age, and sex and is presented below:

Women: BMR = 655 + (9,6 * weight in kg) + (1,8 * height in cm) – (4,7 * age in years)

Men: BMR = 66 + (13.7 * weight in kg) + (5 * height in cm) – (6,8 * age in years)

My calculation, as an example: BMR = 655 + (9,6 * 66) + (1,8 * 174) – (4,7 * 40) = 655 + 633,6 + 313,2 – 183,3 = 1.413,80kJ/day.

Total energy expenditure – used standardised formula is called Harris Benedict Equation and it is calculated by multiplying your BMR with your physical exercise factor. Althought it is an estimation of total energy consumption, this method is relevant in general for normal individuals, that are not at the limits of the bodyweight intervals (not obese, nor very lean and muscular).

Therefore, in order to determine your energy consumption, multiply your BMR with one of the physical exercise factors below that best suits you:

  • Sedentary (very little physical exercise to not at all) * 1,2;
  • Lightly active (1-3 days/week sports or light physical exercise) *1,375;
  • Moderately active (3-5 days/week physical activity) * 1,55;
  • Very active (6-7 days/week intense physical activity) * 1,725;
  • Extra active (intense physical exercise and physical job or 2xtraining) * 1,9.

My calculations: 1.413,80 * 1,55 = 2.191.39 kJ/day.

And here it is, the expression of macronutrients in kJ/cal (1 cal = 4,2 kJ), for your reference:

  • Carbohydrates – 16,7 kJ/gram (4 cal/gram)
  • Proteins – 17 kJ/gram (4 cal/gram)
  • Lipids(fats) – 37,7 kJ/gram (9 cal/gram)

 

*Australian Institute of Personal Trainers – Certificate III in Fitness, Nutrition – Module 1

*Certificate III in Fitness | Nutrition – Module 1- AIPT

*Certificate III in Fitness | Nutrition – Module 2- AIPT

https://fitness.org.au/

http://www.who.int/en/

http://www.mayoclinic.org/

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