If you’re looking to get started on a new diet and/or fitness plan, you want as much data as you can get your hands on. Your daily caloric needs should form a part of this: this is one of the most important pieces of information you will need.
Working out your caloric needs means working out how many calories you need for any given health and fitness goal. Knowing this will be the only realistic way you will be able to change your body composition.
Basal metabolic rate
Your basal metabolic rate (BMR) is the main number you will need to find when working out your caloric requirements. The human body uses up calories even at rest, as basic human functions like breathing, repairing muscle tissue, cell regeneration and renewal, alongside the processing of nutrients and oxygen, all use a lot of energy.
Your BMR is the number of calories that your body needs in order to fulfil all of these functions. Once you know this figure, you will be able to bring about any changes to your body’s composition that you want.
In simplistic terms, if you want to lose weight, you will need a caloric deficit (fewer calories per day than your body uses). Conversely, if you want to gain weight, you will need a caloric surplus (more calories per day than your body uses). Use GymNation's calorie calculator to help you lose weight!
This means adding or deducting calories to your BMR and eating that many in any given day.
It’s easy enough to find a fairly accurate BMR estimate. Though actual amounts will vary according to person, with far too many variables to take into account for any calculator to be 100% accurate all the time, a simple calorie calculator will be able to put you in the right rough area.
There are a few different equations that we can use to find the body’s BMR, with the Harris-Benedict and Mifflin-St Jeor being the main two most often used.
The Harris-Benedict Equation was one of earliest equations written for BMR. It was revised in 1984 to be more accurate and was used up until 1990, when the Mifflin-St Jeor Equation was introduced. The Mifflin-St Jeor Equation also calculates BMR and has proven more accurate a lot of the time than even the revised Harris-Benedict Equation.
The Mifflin-St Jeor and Harris-Benedict equations remain the two most commonly used BMR equations with most calorie calculators. They are:
Mifflin-St Jeor Equation
For men: BMR = 10W + 6.25H - 5A + 5
For women: BMR = 10W + 6.25H - 5A - 161
Revised Harris-Benedict Equation
For men: BMR = 13.397W + 4.799H - 5.677A + 88.362
For women: BMR = 9.247W + 3.098H - 4.330A + 447.593
W= weight in kilograms, H= height in centimetres, A= age in years
The number you get from either of these is an approximation of your basal caloric needs- the number of calories you need to intake in a single day to maintain your bodyweight, without accounting for physical activity.
This value will then need to be multiplied by a physical activity factor (generally 1.2-1.95), which will depend on your typical levels of activity. This will then give you a more accurate more realistic value for maintaining your current bodyweight.
To include the number of calories you burn during daily activities based on your lifestyle and activity levels, a calorie calculator will make use of some variation on the following multiplications:
- Sedentary:If you get little or no exercise, multiply your BMR by 1.2.
- Lightly active.If you lightly exercise one to three days per week, multiply your BMR by 1.375.
- Moderately active.If you moderately exercise three to five days per week, multiply your BMR by 1.55.
- Very active.If you take part in hard exercise six to seven days per week, multiply your BMR by 1.725.
- Extra active.If you engage in very hard exercise six to seven days per week or have a physical job, multiply your BMR by 1.9.
The number you will get from this is the number of daily calories you need in order to maintain your current weight, at your height, weight and age, with your physical activity levels.
It’s important to note, however, that these are rough guides. You may need to experiment with the numbers to better suit your needs as you go along. For example, if you’re putting on unwanted weight, you will need to decrease calories. Try decreasing by 100 calories per day per week until your weight stabilises. If you’re losing unwanted weight, increase calories by the same amount until your weight stabilises.
You can use this calorie calculator to work out how to use caloric intake to meet your health and fitness goals, to lose weight or gain it.
Generally speaking, it will take an average daily surplus deficit of 500 calories to gain roughly 1lb (0.5kg) per week. It will take an average daily caloric deficit of 500 calories to lose roughly 1lb (0.5kg) per week.
Therefore, for example if your BMR is 2,000, you will need to eat around 1,500 calories per day to lose 1lb/0.5kg per week. You would need to eat around 1,000 calories per day to lose 2lbs/1kg (any more than this is not recommended and should only be attempted under medical supervision).
Again, conversely, were you looking to gain weight, you would want to eat around 2,500 calories per day to gain 1lb/0.5kg per week, or 3,000 to gain 2lbs/1kg.
In this way, we can use BMR, calorie calculators and calorie tracking to make sure we are always eating what we need to be to get the results we want.
Do note, however, that calorie content isn’t the end of the story. What those calories are made up of will have a bearing on your health and fitness levels. Make sure that your diet is comprised of healthy foods: plenty of complex and fibre-rich carbohydrate sources, lean, complete protein sources and unsaturated fats.
Eat this way, to the amount dictated by a calorie calculator, and exercise efficiently, and your progress will simply become a waiting game.