There are many great sites online that allow you to calculate your health status regarding to weight and physical activity... and they do it within seconds! Like these links on
WebMd,
SELF,
CalorieCount or
CaloriesCount and many more...
Ever wondered how they do it? What calculations and what logic is behind it? I did!! So I sat down, studied around and started crunching numbers... Let's get to it!
STEP 1)
No matter if you are trying to gain, maintain or loose weight, an objective measuring factor of what you SHOULD do to truly be healthy in regard to your weight is the
Body Mass Index (BMI): 
There is a simple chart (but there are
more elaborate ones too) that tells you how to interpret this BMI number:
Just to make the calculations easy let's say your friend BOB weighs a 100kg and is 2 meters tall: then his BMI will be 100 divided by 4 which equals 25. Same will work with pounds and inches (try it! :-))... BOB is exactly on the line between being overweight but let's just cut him some slack and say that he can consider himself a person of a healthy weight.
Once you determined your BMI you know exactly where you stand: Am I overweight or obese and need to loose weight? Am I underweight and need to try to put on some weight? If you are lucky you are in the healthy weight range and only need to maintain your weight as is.
STEP 2)
In a next step it would be helpful to find out what my daily calorie-intake should be in order for me to maintain, lose or gain weight: This can be done by calculating your
Basal Metabolic Rate (BMR) or Resting Metabolic Rate (RMR).
When we say metabolism, we refer to all the basic processes that the body needs to purely function like breathing, blood circulation, controlling the body temperature, cell growth, brain and nerve function, contraction of muscles etc. All these processes that happen automatically in our body already burn some calories before we even move a toe (AWESOME!!!).
The BMR measures this energy based on your age, gender, weight and other factors. There is an elaborate
equation that can help you calculate your BMR:
So let's try to calculate BOBs BMR. We said he was 100kg and 2m and lets add his age of 30 years which will make the equation look like follows:
BMR = 66+(13.7x100)+(5x200)-(6.8x30) = 66+1370+1000-204 = 2232 calories.
So BOB burns 2232 calories every day just by simply existing: lucky guy, eh!?
STEP 3)
OK, so far so good:
We know what we need to do based on our BMI (maintain, lose or gain weight)
and we know how much energy we burn simply by existing based on your BMR.
What missing is considering our daily activity level to then be able to determine our daily calorie requirements... The missing variable needed is the
Physical Activity Level (PAL).
NOW comes the time you need to be honest with yourself: how active am I? Not in your imaginary life... Not in the world of dreams... Not in the form of "should've, could've, would've"... BUT in actual reality!!!! Oh, oh...
STEP 4)
The final step is to calculate what your
Daily Calorie Intake (DCI) should be. This is the easiest calculation in the form of the following simple multiplication:
This calculation will give you the approximate number of calories you need to consume on a daily basis to MAINTAIN your weight.
What would BOBs DCI amount to? Let's assume that he is moderately active in his daily life and exercises 3 to 5 times a week. The the calculation would be as follows:
DCI = BMR x PAL = 2232 x 1.55 = 3348
So BOB can happily eat 3348 calories worth of yummy food to maintain his 100kg weight that he started with.
Now to modify this for gaining or losing weight is easy:
If you want to GAIN weight, you need to consume more calories then what you burn.
If you want to LOOSE weight, you need to burn more calories then what you consume.
The general rule is that you need to cut down or add about 3500 calories to lose or gain 0.5kg per week - a.k.a. about 500 calories a day.
Keep in mind though that not each calorie is of the same nutritional value! Check out my previeous post regarding
Calories VS Nutrients to find out more about that :-)
SORRY to tell you this:
but after reading all the way down here;
after now knowing exactly where you stand in regard to weight, activity level and necessary calories...
THERE ARE NO MORE EXCUSES!
You're welcome :-o
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