Barbara Bowman's Blog

Body fat measurements and the measuring tape are recognized as superior methods for measuring "weight loss". When one declares that they want to "lose weight", what they often mean is that they want to lose fat. So what does the number really mean?

First, your body fat percentage is simply the percentage of fat your body contains. If you are 150 pounds and 10% fat, it means that your body consists of 15 pounds fat and 135 pounds lean body mass (bone, muscle, organ tissue, blood and everything else).

Fat regulates body temperature, cushions and insulates organs and tissues and is the main form of the body's energy storage. For the body to function normally and healthily a certain amount of body fat is required. This is called essential fat. For women the amount of essential fat is 10-12% of bodyweight and for men it is 2-4%.

Knowing your body fat percentage can help you determine if your weight loss goals are realistic. Remember, weight loss doesn’t always mean fat loss. For Example:
Let's say you're a 130lb woman with 23% body fat, and you goal is to "lose 20 pounds":
Initial body fat: 130lb x 0.23 fat = 30lb body fat
Lean body mass: 130lb total – 30lb fat = 100lb lean body mass (bones, organs and all else)
Goal: 130lb – 20lb = 110 pounds

As you can see, the goal of losing 20 pounds is not realistic or healthy. At 110 pounds, this woman still requires 100lb of lean body mass (bones, organs, etc.), but would only be carrying 10lb, or only 9% body fat. This is a dangerously low percentage.

A better goal might be for the woman to reduce her body fat from 23% to 18%. In this case:
100lb lean body mass ÷ .82 (100% - BF Goal) = 122lb

So, for this individual to achieve a lean, but healthy 18% fat, she would need to lose only 8 pounds of fat, reducing her weight from her current 130 pounds to 122 pounds. Losing more than 8 pounds means losing lean body mass (usually metabolically-active muscle tissue), which is clearly not desirable.

So before you decide that you need to "lose weight", remember to consider that "weight" consists of both lean body mass and body fat. Try to keep your weight loss goals realistic, and remember, keep the calorie-burning muscle, and lose only the fat.