Body fat percentage is generally accepted as a better gauge of fitness than weight.When in ideal shape, body fat will make up about 14% - 17% of a male's body weight and 21% - 24% of a female's. The remainder of the body's weight is composed of water (55%-60%), muscle and other lean tissue (10%-20%), and bone and minerals (6%-8%). 

In other words, a 150-pound woman who is within or close to her ideal body fat composition range at 22% will have approximately 33 pounds of fat, 86 pounds of weight composed primarily of water, 20 pounds of muscle and other lean tissue, and 11 pounds of bone and mineral weight. This total then makes up her total weight of 150 lbs. 

Now take the example of another woman who weights 150 pounds, but has 30% fat on her body. She would have 45 pounds of fat on her body, and the rest of her weight would be divided among muscle, bone and water. Her non fat body composition might look like this, 79 pounds of water (53%), 17 pounds of muscle (12%), and 9 pounds of bone and minerals (6%). Both women weight 150 lbs. and are about the same height, but one looks much different because she has less body fat.

Appearances Can Be Deceiving 
Men A, B and C are exactly the same height. A and B have the same weight, and C weighs considerably more. For his height C appears to be fat. But after analyzing body fat levels, B and C have acceptable percentages while A has above the recommended range and is at a higher health risk.

Medical professionals have determined that a healthy range of body fat is 14%-20% for men, and 17%-24% for women. But until recently, accurate methods for measuring and monitoring body fat have not been available to the average person.

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. The following table describes body fat ranges and their associated categories:

Knowing your body fat percentage can also 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 130 pounds woman with 23% body fat, and you goal is to "lose 20 pounds":
Initial body fat: 130 pounds x 0.23 fat = 30 pounds body fat Lean body mass: 130 pounds total - 30 pounds fat = 100 pounds lean body mass (bones, organs and all else) Goal: 130 pounds - 20 pounds = 110 pounds

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

b A better goal might be for the woman to reduce her body fat from 23% to 18%. In this case:
130pounds x 0.18 = 23 pounds body fat
100 pounds lean body mass + 23 pounds body fat = 123 pounds goal weight

So, for this individual to achieve a lean, but healthy 18% fat, she would need to lose only 7 pounds of fat, reducing her weight from her current 130 pounds to 123 pounds. Losing more than 7 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.

Tips:
The suggested level of body fat for a female athlete is 14 to 20 percent; for male athletes, it's 6 to 13 percent. The ideal depends greatly on the requirements of the sport.

For that "gotta have body," shoot for a body fat percentage between 21 and 24 percent for women, and from 14 to 17 percent for men. But anywhere from 25 to 31 percent for women, and 18 to 25 percent for men, is considered healthy. 

If you're a woman and your body fat is more than 32 percent of your weight, or if you're a man and your body fat is more than 25 percent of your weight, that's a sign of obesity. Individuals in this range should seek the advice of a health care provider to begin a weight loss and exercise program. 

Warnings:
Always check with your doctor before beginning a weight loss or exercise program.
Women need at least 10 to 12 percent body fat to maintain healthy bodily functions and continue having periods; men need at least 2 to 4 percent to maintain essential bodily functions.