Weight Loss vs. Fat Loss
Although this trend is changing recently, most diet books tend to only talk about weight loss and I suspect that most dieters only think in terms of weight loss.
Weight versus fat loss: they are not the same thing
Every tissue in your body (including muscle, body fat, your heart, liver, spleen, kidneys, bones, water, minerals etc.) weighs a given amount. We could (conceivably anyhow) take each of them out of your body, plop them on a scale and find out how much they weigh. Your total body weight is comprised of the weight of every one of those tissues. But only some portion of your total weight is fat. For this reason, researchers and techie types frequently divide the body into two (or more) components including fat mass (the sum total of the bodyfat you have on your body) and lean body mass (everything else). While there are different ‘types’ of body fat, this is more detail than we need.
Let’s say that we could magically determine the weight of only your fat cells. Of course, we know your total weight by throwing you on a scale. By dividing the total amount of fat into the total bodyweight, you can determine a body fat percentage which represents the percentage of your total weight is fat.
Lean athletes might only have 5-10% body fat, meaning that only 5-10% of their total weight is fat. So a 200 pound athlete with 10% bodyfat is carrying 20 lbs. (200 * 0.10 = 20) of body fat. The remaining 180 pounds (200 total pounds – 20 pounds of fat weight = 180 lbs.) is muscle, organs, bones, water, etc. Researchers call the remaining 180 pounds lean body mass or LBM. In cases of extreme obesity, a bodyfat percentage of 40-50% or higher is not unheard of. Meaning that nearly one-half of that person’s total weight is fat. A 400 pound person with 50% bodyfat
is carrying 200 lbs. of bodyfat. The other 200 pounds is muscle, organs, bones, etc. Again, 200
pounds of LBM along with 200 pounds of fat.
Most people fall somewhere between these two extremes. An average male may carry from 18-23% bodyfat and an average female somewhere between 25-30% bodyfat. So a male at 180 lbs. and 20% bodyfat is carrying 36 pounds of fat and the rest of his weight (144 lbs.) is LBM. A 150 pound female at 30% bodyfat has 50 pounds of bodyfat and 100 pounds of LBM.
Healthy levels of bodyfat are somewhat up to debate but most ‘authorities’ recommend 11-18% as being optimally healthy for males and 18-25% as being optimal for females.
Why is this important?
So let’s say you start a diet, reducing some part of your daily food intake. Maybe you start exercising, too. After some time period, you get on the scale and it says you’ve lost 10 lbs.. That’s 10 lbs. of weight. But how much of it is fat? Frankly, you have no way of knowing with just the scale (unless it’s one of those Tanita bodyfat scales, which attempt to estimate bodyfat percentage but don’t work very well in my opinion). You could have lost fat or muscle or just dropped a lot of water. Even a big bowel movement can cause a weight loss of a pound or two (or more, depending). A colonic that clears out your entire lower intestinal tract may cause a significant weight loss. The scale can’t tell you what you’ve lost, it can only tell you how much you have lost.
When you’re worrying about long-term changes, the real goal is fat loss (some LBM loss is occasionally acceptable but that’s more detail than I want to get into here). That is, cycling water weight on and off of your body (as frequently happens with certain dieting approaches) isn’t really moving you towards any real goal even if makes you think you are