Saturday, 12 September 2009

Weight loss mathematics

Being roughly half way through my weight loss programm, I thought I'd indulge myself in a little bit of mathematics to get an idea of where I might get to.

What I wanted to see is where my body fat percentage might end up if I hit my 85kg target.

To calculate this, I'll need to make an estimate of the proportion of weight I'm losing which is made up of fat, and how much from lean tissue mass. I'll also need to know my starting body fat percentage.

Well I reckon when I started this weight loss initiative that my body fat percentage was around 22% - this is at least what some scales in my holiday home say (I don't have body fat measuring scales at my normal home).

And reading a couple of research reports into restricted and very low calorie diets, it appears that between 80% and 90% of weight loss is from fat with the remainder coming from lean body mass.

So, putting all of that together gives me the following prediction - if I get to 85kg (my goal weight) then I'll have 9% body fat. Not the most amazing in the world, but equally well lower than average and it should mean that I'd have plenty of definition in my muscles.

So, here is the working:

At the start of this exercise, I was 102kg with 22% body fat - so lean mass was 79.6kg and body fat was 22.4kg (I hate to think what that would look like if made out of butter...)

If I lose 17kg and 80% of the weight loss comes from fat, then I will lose 14.4kg of fat and 2.6kg of lean body mass.

Therefore, I'll be left with 8kg of fat and 77kg of lean body mass with a total mass of 85kg - this equates to 9% body fat.

All very interesting in theory - so let's see if:

  1. I can get down to 85kg

  2. 80% (or hopefully more) of my weight loss is in the form of fat

  3. I was only 22% body fat when I started this and not substantially more!

I'm not sure how long it will take to get down to my goal weight - I think it'll take me at least until the end of October - stick with me and we'll see if my calculations are right!