Well, this is a loaded question and the answer reflects the controversy surrounding the issue. A better question might be, "What is my ideal weight?"   Although body fat percent varies considerably for men and women, for age and culture, for those involved in different sports activities and even for different geographic location, there are some standards. The minimum percent body fat considered safe and acceptable for good health is 5% for males and 12% for females. However, the average adult body fat is closer to 15%-18% for men and 22%-25% for women.

Athletes typically find themselves at the low end of this scale. Optimal levels of body fat are much lower for those striving for high level performance. Ranges for professional athletes are quite a bit lower than for the average, healthy individual. Much of this difference can be attributed to the increased lean weight (muscle mass) of top athletes. The impact of body size on performance is one consideration that may correlate with body fat.

While levels of body fat seem to be related to performance, body composition alone has never been a great predictor of sports performance. Several studies have suggested that percent body fat is inversely related to maximal aerobic capacity and to distance running performance. Lean muscle mass seems to be positively related to performance in sports where the ability to generate maximal force is required  which might help explain why a lot of those defensive linemen appear to have a high body fat levels. The body fat percentage for elite athletes vary largely by sport. The association between low body fat and improved performance is not precise and there is little evidence of performance benefits when male athletes drop under 8% and women drop under 14% body fat.

Swimmers also throw a curve ball into this generally accepted notion of endurance athletes having lower body fat levels. Swimmer's "body fat mystery" as it is now known, grew out of the recognition that competition level swimmers have a higher body fat than most other athletes. Cyclists, however, with superior aerobic power-to-weight ratios will gain advantages in hill climbing performance.

In general, the normal healthy range of body fat percentage changes based on age. Therefore, we have assigned a percentile number for the healthy range. The number for which we generally feel there is no health advantage to getting any lower in body fat is the 70th percentile in the left column of the chart that you may download. Anything lower will not necessarily increase your health as related to body fat percentage even though you will get leaner and more vascular. On the other hand, anything higher than the 70th percentile does tend to increase your potential for the adverse health issues as related to high body fat percentage such as: Coronary Heart Disease, Diabetes, Increased Blood Pressure, Increased Total Cholesterol Level, Increased LDL (bad) Cholesterol, Hardening of the Arteries, Increased predisposition to some cancers, etc. etc. The higher your percentage is, the higher your potential for these illnesses become as you age. The long and short of it is, if a person is and stays obese, his/her life will be shortened by approximately 13 years.

Obesity, or excessive body fat, is generally defined as a value greater than 30%. However, the detrimental health value of obesity does have a relationship to your age. It is far more severe to be at or above 30% at age 50 years old than it is at 20 years old.