When changing eating habits, cutting down on sweets and salty snacks, and adding physical activity don’t help you lose weight, it’s a good idea to accurately determine your energy demand and then estimate how many calories you should actually take in per day to reach your goal. Only providing fewer kilocalories than the body expends during the day will bring you closer to your dream figure.
How do you calculate your requirements?
The basis for calculating calorie requirements is to determine our total energy expenditure during the day. To calculate the Total Metabolic Rate (TMR), we should first calculate the Basal Metabolic Rate (BMR) and then multiply it by the corresponding physical activity level. Thus:
Total Metabolic Rate (TMR) = Basal Metabolic Rate (BMR) x Physical Activity Level (PAL)
Now let’s explain what the different elements are. BMR is the lowest level of energy metabolism occurring in the human body. Energy from the BMR is used to maintain basic life processes, such as respiration, blood circulation and heart rate. The Harris-Benedict or Mifflin equations can be used to calculate BMR.
Mifflin equation:
- BMR (women) = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161
- BMR (men) = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5
Harris-Benedict equation:
- BMR (women) = 655.1 + (9.563 x body weight in kg) + (1.85 x height in cm) - (4.676 x age in years)
- BMR (men) = 66.5 + (13.75 x body weight in kg) + (5.003 x height in cm) - (6.775 x age in years)
And what is physical activity? Contrary to appearances, the term does not include only training at the gym or playing sports. Physical activity includes walking, climbing stairs, and even household chores – we lose calories on these, too!
The following activity levels are assumed:
- 1.2-1.3 –> for a bed-ridden patient
- 1.4 –> for low physical activity
- 1.6 –> for moderate physical activity
- 1.75 –> active lifestyle
- 2 –> very active lifestyle
- 2.2-2.4 –> doing sports professionally
The calorie content of the diet depends on the goal
After calculating the TMR, it is necessary to make modifications to the calorie content of our diet plan depending on our goal. If you want to gain weight or build muscle mass, you add the appropriate number of calories to the TMR. Often it is around 200-300 kcal a day more. We do the opposite when we want to lose weight. Then some calories should be subtracted from the TMR, depending on the starting weight and physical activity level. The usual recommendation is to “cut” about 300-600 kcal, and in the case of obese people even 1000 kcal per day. Another assumption might be to reduce TMR values by 10-20%.
But note! It is not worth drawing conclusions on the potential end result after the first weeks of the diet, when the weight loss is definitely greater. Weight loss should be gradual and stable (this usually happens only in the next stage of the process), and the decrease should be about 0.5-1 kg/week. It also happens that weight loss is not noticeable on the scales, but is clearly visible when taking circumference measurements of body parts (such as the thigh, calf, waist or abdomen).
Confirmation from a specialist
For the diet to achieve its goal, the calorie content of the plan should be calculated individually. While using the aforementioned equations should not pose a major problem, estimating the appropriate level of physical activity can cause doubts, as well as introduce a fair amount of error in the calculations. So it’s always a good idea to consult your needs with an experienced dietician.
References:
- Gawęcki J. (ed.): Żywienie człowieka, podstawy nauki o żywieniu. Wydawnictwo Naukowe PWN, Warszawa 2012
- Jarosz M., Rychlik E., Stoś K., Charzewska J. (eds.): Normy żywienia dla populacji Polski i ich zastosowanie. Narodowy Instytut Zdrowia Publicznego - Państwowy Zakład Higieny, 2020
- Bean A.: Żywienie w sporcie, kompletny przewodnik. Wyd. Zysk i S-ka, 2014