Via Andy of RippedBody;
A common question we see is “How do I calculate how many pounds I need to lose?”
Say a 180-pound individual at 15./. B.F wants to get to 10./.. Assuming his weight loss is 75./. fat and 25./. lean body mass, how many pounds will he have to lose?
For most people, for every 1./. of B.F they want to drop, they need to lose roughly 2 pounds. However, this heuristic breaks down at the edges, so let's get more granular...
First, we'll simplify this by ignoring water, gut content, and glycogen changes, which can easily affect your weight by 3–7 pounds depending on body size. We can come back to this later.
Assumption:
Muscle mass will be neither lost nor gained.
So weight change = fat change. (Yes, I'm pushing back against what was suggested above about 25./. of the weight loss coming from muscle mass.)
Reasons for the assumption that muscle won't be gained or lost:
You're not new to training. (So you can't expect to gain significant muscle.)
Your target B.F isn't less than 10./. . (It gets increasingly hard to hold onto muscle mass past this point.)
You train appropriately hard. (This is the most important tool in our arsenal to tell the body to hold onto muscle while in a calorie deficit.)
You don't lose weight too fast. (Keep it in the 0.5–0.75./. of body weight per week range.)
You eat enough protein. (At least 1g per pound of target body weight should be sufficient.)
Math to find total weight loss needed:
If you're 180 lbs at 15./., you'll be X lbs at 10./..
Fat free mass = 180 * (1 - 0.15) = 153 lbs
When at 10./., fat free mass = X * (1 - 0.1)
153 = X * 0.9
X = 153 / 0.9 = 170 lbs
This means you'll need to lose 10 lbs.
So if we write this out to be a general formula:
End Body Weight = [Current Body Weight * (1 - Current Estimated B.F Percentage as a decimal)] / (1 - Target B.F Percentage as a decimal)
Let's "gut check" the math:
If you are 20./. B.F and want to get down to 12./. and weigh 200 lbs.
End Body Weight = 200 * 0.8 / 0.88 = 182 lbs
…which sounds about right.
But remember to take into account gut content, water, and glycogen!
If you haven't started dieting yet, you won't have had the initial drop of water, gut content, and glycogen.
So, your weight will be 3–7 lbs lower by the time you finish cutting, which will return once you're back at calorie maintenance.
In first example, 180 lbs at 15./., targeting 10./., you'll end your cut at ~163–167 lbs coming back to ~170 lbs once back at maintenance.
In the second example, 200 lbs at 20./., targeting 12./. you'll end your cut at 175–179 lbs, returning to ~182 lbs once back at maintenance.
This catches people off guard and leads them to believe they've lost muscle mass as they have to get far lighted than they imagined.
Further, there is a stupid societal pressure on men to think they all need to be 6./. B.F at 200 lbs (regardless of height) to look good, which is ridiculous unless using AAS
Part of the battle is using the scale, not letting the number use you.
RippedBody.com
