How to Calculate Your Daily Calorie Need
In this article, I will illustrate an easy, step-wise way to calculate your daily calorie need, which is the foundation of setting a solid nutritional plan, whether you want to increase strength and performance, lose weight, or gain muscle and decrease body fat, or simply improve your overall health and wellbeing. There are two basic components to consider, namely your individual resting Metabolic Rate, or RMR, and your personal Physical Activity Level, or PAL. The third aspect that will influence your unique target calorie need is your personal goal, namely whether you want to maintain your weight, decrease or increase it overall.
Resting Metabolic Rate (RMR)
As we know, a calorie (also often used interchangeably with kcal, or kilocalories) is a unit of energy used in the Imperial system of measurement. The equivalent in the Metric system is a kiloJoule or kJ abbreviated. Calories are the energy we acquire from our food and drink and the energy is made available to sustain the necessary body functions and physical activity. The RMR is the energy needed to sustain the body’s necessary functions:
- the synthesis, secretion, and metabolism of enzymes and hormones
- maintenance of body temperature
- brain function
- work of the cardiac and respiratory muscles
- cell function and replacement
The RMR accounts for about 60-80% of a person’s total energy requirements, with the balance made up by the thermic effect of food – ingestion, digestion, absorption, and transport of nutrients, roughly 10%, and 15-30% expended on physical activity.
Age, gender, and weight factors are used to predict a person’s RMR, using an equation based on an empirical study of 5,000 healthy adults. The reference table to calculate RMR by age and gender is as follows.
For example, the RMR of Jason, a 24-year-old male athlete weighing 100 kg, is estimated to be:
RMR = (15.3 x 100) + 651, or 2,181 kcal.
This means that Jason requires 2,181 kcal or 9,125 kilojoules of energy daily to satisfy his body’s essential functions.
Physical Activity Level (PAL)
The next step is to determine a person’s physical activity level, or PAL, according to the table below.
The most activity level of a male or female is selected and the corresponding average factor (or a number inside the range provided) is used to multiply with his or her RMR to determine the daily calorie need. The determination of the best activity level class is discretionary according to the following guidelines:
- Sedentary or light activities: Sedentary occupation and lifestyle – Sleeping Eating, Non-strenuous Working, Cooking, Sitting
- Light or moderately active: Sedentary occupations but with regular physical activity, 3-4 times a week for an hour
- Heavy or very heavy activity: Regular strenuous work or leisure activity for several hours most days of the week
The daily calorie requirement equals RMR multiplied with PAL.
Daily calorie need = RMR x PAL
Using Jason again as an example, as he does strength training in the gym for an hour four times a week and works in an office during weekdays, his activity level is light or moderate. As he does not do cardio exercises or intense hypertrophy training, his activity level falls toward the light side. Applying the average, we use a PAL factor of 1.5 for the calculation.
Therefore, Jason’s daily calorie need is:
RMR x PAL = 2,181 kcal x 1.5 = 3,271 kcal (or 13,688 kilojoules)
Reassessing Daily Calorie Need
It is prudent for a person to reassess his or her calorie needs every four to six weeks as it can change with changes in factors such as weight, routine, or training regime (frequency, duration, and intensity).
In a next article, I will explain how to break the total daily calorie need into an appropriate macronutrient composition to determine the recommended carbohydrate, protein, and fat intake ratio. Also, just as a reminder, the calculated calorie need is appropriate for someone wishing to maintain their current body weight. Considerations and calculations to reduce or increase body weight will also be covered in a follow-up article. Please be sure to subscribe to receive automatic updates of new contents.