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Calculating Your Calorie Intake
Before you begin any type of healthy eating program or diet, you should think about how many calories you actually need and what that means for your daily intake. There are lots of different online calculators, such as My Fitness Pal, that can estimate your calories using your height, weight and age. However, these have a wide range of error so using a more detailed equation is much better to find your correct amount.
The Harris-Benedict equation is one of the best methods to use, and the equation is as follows:
MenBMR = 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) - (5.677 x age in years)
WomenBMR = 447.593 + (9.247 x weight in kg) + (3.098 x height in cm) - (4.330 x age in years)
This gives you your basal metabolic rate (BMR), which is the amount of calories you need to sustain life at total rest, therefore once you have your BMR we need to multiply it by an activity factor to give the correct amount you need per day. Multiple your BMR by one of the following to get your total calorie demand.
- Little to no exercise: = BMR x 1.2
- Light exercise (1–3 days per week) = BMR x 1.375
- Moderate exercise (3–5 days per week) = BMR x 1.55
- Heavy exercise (6–7 days per week)= BMR x 1.725
- Very heavy exercise (twice per day, extra heavy workouts) = BMR x 1.9
For example, a female aged 35 weighing 65kg at 160cm tall would need:
447.593 + (9.247 x 65) + (3.098 x 160) - (4.330 x 35) = 1393. We then need to multiply this by her activity factor, let's assume she only exercises twice a week, so we multiply the result by 1.375:
1393 X 1.375 = 1915 calories per day to maintain her weight.
How Many Calories Do I Need To Lose Weight?
So now we know how many calories our female needs per day to maintain her weight, but how many calories should you take in to actually lose weight?
It is proven that to lose one pound of fat per week you need to burn or have a deficit of 3500 calories. This equates to 500 less calories per day to enable you to lose a pound a week. For a pound and a half you would need a daily deficit of 750 calories. There are various ways to get a daily deficit in your calorie's, either by restricting your diet to a much lower number — in the case of our example, if she was to lose 1.5lb a week, she would need to be taking in 1165 calories per day. She could also be burning at least 250 calories in the gym while restricting her diet to 1415 calories.