Step 1. Estimating Your Basal Metabolic Rate (BMR)
To estimate your BMR you can choose your pick of the predictive metabolic equations. None of them will get it spot on to the calorie as this would require you spending the night in an expensive lab known as a metabolic ward. However, predictive metabolic equations will get you in the ballpark usually within 10% give or take of your energy needs.
The one that has been shown to have the most accuracy in the research when compared against the others is known as the Miffen St. Joer. Here is how it looks for men and women:
10 x weight (kg) + 6.25 x height (cm) – 5 x age (y) + 5 = BMR
10 x weight (kg) + 6.25 x height (cm) – 5 x age (y) – 161 = BMR
Using the above equations, a male weighing 90kg, 180 cm, aged 35 and a female weighing 70kg, 155 cm, aged 30 would have a BMR of 1855 calories (male) and a female would 1357 calories. If you did not have all your statistics to hand a simplified version can also be used by multiplying your weight in Kg by 22.
Step 2: Adjust For Activity Status
Once you have your BMR worked out, it is now time to factor in your activity status. As most don’t do some type of activity during the day be it go the gym or go to work and everything in between, this invariably burns energy/calories and should be accounted for even if it is just going to work and coming come. The figures below can be used to determine this.
>If you are sedentary (little or no exercise) = BMR x 1.2
>If you are lightly active (light exercise/sports 1-3 days/week) = BMR x 1.375
>If you are moderately active (moderate exercise/sports 3-5 days/week) = BMR x 1.55
>If you are very active (hard exercise/sports 6-7 days a week) = BMR x 1.725
>If you are extra active (very hard exercise/sports & physical job or 2x training) = BMR x 1.9
For most, the lightly or moderately active will likely be a good fit. Using the male BMR figures in step 1 and the moderately active figure this would bring our calories to 2875 (1855 * 1.55). This figure is known as your total daily energy expenditure (TDEE). Now only you know what your lifestyle looks like so choose what you feel represents your lifestyle.
Step 3: Adjust For Fat Loss
It requires around 3500 calories of a deficit to lose a pound of fat. Therefore, to lose a pound of fat per week, subtracting 500 calories (3500/7 = 500) from TDEE figure factors in that you want things going towards a negative energy balance in order to achieve this. Using the figures in step 2 would leave you with a final calorie figure of 2375 (2875 – 500).
I cannot emphasize enough that this is just an estimate and you will have to adapt as things proceed. It’s highly possible that someone could eat this amount of calories and stay the same weight after a week or two, this would be valuable feedback though as calories would just need to be tweaked again (provided no additional exercise was being added) in order to elicit fat loss. Many do not spend time finding out what their maintenance calories are and find themselves with an approach that is unsustainable. This way you are finding out what your “calorie budget” is allowing you to be more precise in what you can eat up to and still make progress as you’re doing it.