Hi all,

I'm really struggling with a percentage problem for a new spreadsheet I'm developing to support me achieving my fitness and weight goals. I'm hoping to develop something which will help others to lose weight as I think I have a really good system for losing and maintaining weight. Here goes:

I'm trying to calculate how many weeks it will take me to achieve mybody fatgoals following the nutrition programme I've just designed. The measure I'm struggling with is called 'Lean Body Mass' which is essentially yourweightminus youBody Fat Mass; here's an example:

Weight in kg: 71kg

Body Fat Percentage (BFP): 12%

Body Fat Mass = Weight – (Weight*BFP), or in my example Body Fat Mass = 71-(71*0.12) = 8.5kg, therefore,

Lean Body Mass = Weight – Body Fat Mass, i.e., Lean Body Mass = 71-8.5 = 62.5kg

The complexity comes in when I try to calculate what my targetBody Fat Massis should my BFP be 7%. It sounds easy because we know what my Lean Body Mass is, but you can't just add 7% to BFP as it gives an incorrect figure. For example, if we try to reverse engineer the first problem it works out like this:

Weight = Lean Body Mass * BFP, or in our example, Weight = 62.5*1.12 = 70kg. The unknown factor is theso this causes the problem.total new weight

In summary, I need to know how to calculate my 71kg starting weight from my Lean Body Mass of 62.5kg and my known BFP of 12%.

Can someone please help as this is driving me crazy?

Thanks, Lee