T Nation

The Weight of Bodyfat?

I was wondering how the actually weight of the fat in your body is calculated… If you were 200lbs and 20% bf… and lost 10% of your bf…then that would mean you lost 20lbs? but doesn’t muscle weigh more than fat so the % of fat in your body doesn’t have anything to do with the weight of your lean muscle?

Im confused

http://www.T-Nation.com/tmagnum/readTopic.do?id=2247547

[quote]Petermus wrote:
I was wondering how the actually weight of the fat in your body is calculated… If you were 200lbs and 20% bf… and lost 10% of your bf…then that would mean you lost 20lbs? but doesn’t muscle weigh more than fat so the % of fat in your body doesn’t have anything to do with the weight of your lean muscle?

Im confused [/quote]

Yup, you sure are. 200lbs at 20%bf= 40lbs fat, 160 lean body mass. if you lose 10% of your body fat, you’ve lost 10% of 40lbs, or 4 lbs. You would weight 196, and have 36lbs of fat, which would give you a bf% of 18%. If you lose 10% of your total weight by losing only fat, you’ve lost 20 lbs of fat, and would be 180 with a bf% of 11%.

A pound of muscle weighs the same as a pound of fat. However, fat is less dense then muscle, so a given volume of muscle would weigh more then the same amount of fat. The % of fat in your body is the ratio of fat to total weight. So the two ways you can lower your bf% are 1. lose fat, 2. gain muscle. For example, if you start at 200lbs and 20%bf, you can lose 4 lbs of fat to get to 18% bf, or you can gain about 22 lbs of muscle without gaining any fat. Then you would weigh 222, have 40 lbs of fat, and a bf of 18%.

Hope that helps.

ya that clears it up nicely

just want to see if I got this right
im 290lbs, about 33% bf
290x.33=95.7
290-95.7=194.3… I’m 6’1 with a Large Frame but I think that must be off by a bit? I’m not that
Strong ect…so my bf% must be off by a alot?

Depends on how you measure your bf%. It may be off by a bit, but 194 lean sounds about right for a 6’1" guy. Remember that strength is partially determined by CNS effecency, so if you’ve just started lifting, even if you have a decent about of muscle, you probably aren’t very good at using them. Also, if you’ve been focused on fat loss, your workouts probably haven’t been geared towards strength gains.

[quote]ninjaboy wrote:
Depends on how you measure your bf%. It may be off by a bit, but 194 lean sounds about right for a 6’1" guy. Remember that strength is partially determined by CNS effecency, so if you’ve just started lifting, even if you have a decent about of muscle, you probably aren’t very good at using them. Also, if you’ve been focused on fat loss, your workouts probably haven’t been geared towards strength gains.[/quote]

That sounds right haha

thanks

It’s not really quite so simple. Suppose you weigh 200 pounds with a 20% body fat. If you lost 20 pounds of only fat, then in theory you would weigh 180 at 10% body fat.

However, even if no muscle is lost, with every pound of fat lost, there is also the losing of water weight (water weight you won’t necessarily gain back). So this loss of 20 pounds might only put you down to say a 15% body fat (this only an example, I don’t know what the real ratio of fat to water loss is).

Although I remember reading that a relatively lean person needs to burn 2000 calories to lose one pound, and a pound of fat is 3500 calories (whereas an obese person would need to burn closer to 3000 calories), so for every four pounds of fat, you’ll also drop 3 pounds of water (assuming you’re pretty lean).

I don’t remember my sources, and I can’t seem to find them, so if anyone else knows more about this, feel free to chime in.

I realize you were just discussing definitions, but I thought this would be useful to you as well.