Too little or too much body weight causes numerous health complications such as cardiovascular disease and impaired metabolism. Maintaining a healthy body weight is a goal for many men. While you can't necessarily transform your weight overnight, you can evaluate your current weight and set healthy goals. Body Mass Index, or BMI, provides fitness information quickly and enables comparison to age and sex norm charts. BMI also classifies your risk for weight-related health complications.
Calculation
As stated in the "American College of Sports Medicine's Guidelines for Exercise Testing and Prescription," BMI assesses weight relative to height and is calculated by dividing body weight in kilograms by height in meters squared. If required, convert pounds to kilograms by dividing your weight in pounds by 2.2, and convert inches to meters by multiplying your height in inches by 0.0254 as suggested by the American College of Sports Medicine. In addition, an online BMI calculator can be found on the American Council on Exercise website.
Function
BMI classifies people as obese, overweight or underweight and identifies individuals at risk for weight-related diseases such as Type 2 diabetes. Simplicity of BMI calculation enables analysis of large populations such as military personnel, firefighters and general population groups. For example, the Centers for Disease Control's National Health and Nutrition Examination Survey found that the average American adult male has a BMI of 26.6. In addition, BMI enables assessment of past populations when height and weight data is available.
Classification
The American College of Sports Medicine classifies men with a BMI below 18.5 as underweight, from 18.5 to 24.9 as normal weight, from 25 to 29.9 as overweight, from 30 to 34.9 as type I obesity, from 35 to 39.9 as type II obesity and greater than 40 as type III obesity. Men with BMI values over 30 are at increased risk for hypertension and high cholesterol. Risk of cardiovascular disease is also increased in men with BMI values below 18.5.
Limitations
BMI fails to distinguish between body fat, muscle or bone. Due to increased density, muscle weighs more than fat and contributes to overall body weight. Therefore, men with a high percentage of muscle tend to be misclassified as overweight or obese. Many athletes and weight lifters avoid BMI as a predictor of body fitness and instead rely on body composition, or body fat percentage, analysis. Although BMI is widely used, it is best when combined with other measurements of fitness.
BMI and Body Fat Percentage
Body fat percentage refers to the percentage of your total weight comprised of body fat. The relationship between BMI and percent body fat in males is affected by age, ethnicity and body build. For example, at a given BMI value, older males tend to have a greater body fat percentage than younger males due to age-related decreases in muscle mass. For these reasons, you cannot accurately predict body fat percentage using BMI alone. Please consult a doctor if you are concerned about your BMI value.
References
- "Advanced Fitness Assessment and Exercise Prescription"; Vivian H. Heyward; 2006
- "American College of Sports Medicine's Guidelines for Exercise Testing and Prescription"; American College of Sports Medicine; 2006
- Centers for Disease Control, National Health and Nutrition Examination Survey: Healthy Weight, Overweight and Obesity among US Adults
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