Body mass index and body fat percentage are two methods of assessing your body composition. They are generally performed to determine if you are overweight or if you carry too much body fat. If you are overweight or carry too much body fat, you are at a higher risk for developing heart disease and other forms of chronic illness.
Body Fat Percentage
Body fat percentage is simply the percentage of your body weight that comes from fat deposited on your body. Body fat can be measured several ways including direct measurement using skin-fold measurements and measuring the waist-to-hip ratio. Once the measurements are taken, the results are compared to standard normals and a percentage is scored based on the comparison. Another way to measure body fat is to perform bio-electrical impedance analysis, which uses a computer and an electrical current to determine resistance, or impedance, to the signal as it travels through your body's muscle and fat. The computer then calculates how much body fat you have. Underwater weighing is performed to determine your body volume by submerging you in a tank of water. While underwater, your density is measured and a calculation is performed that analyzes your body fat density. These tests, which are most accurate when performed by trained professionals, are likely to have errors associated with them.
Body Mass Index
Body mass index or BMI, is an indirect way to determine if your body fat and weight are too high for your body size. It is simple to perform by using a standard calculation. To get your BMI score, you measure your height in inches and your weight in pounds. Take your weight and multiply it by 703 and then divide that answer by your height in inches. Take that answer and divide by your height in inches a second time to get your BMI score. This score is then compared to five categories to determine if your weight is healthy or not.
Five BMI Categories
The five BMI categories are underweight, healthy, overweight, obese and morbidly obese. A BMI score below 18.5 is underweight, and a score of 18.5 to 24.9 is considered healthy. If you score a 25.0 to a 29.9, you are overweight, and a score over 30.0 indicates that you are obese. If you have an even higher score above 40, then you are morbidly obese. MedlinePlus states that obesity is defined as having too much body fat; therefore, a score of 30 or above indicates that your body fat percentage is excessive.
Considerations
BMI and body fat percentage cannot predict health risk, but higher values for both calculations indicate that your health is moving in the wrong direction. To improve your BMI and your body fat, you need to alter your lifestyle by improving your diet, increasing your exercise level, and avoiding foods that contribute to an unhealthy weight. If you have a BMI number that is extremely high, then you need to work with your doctor and a dietitian to help you create a meal plan and a physical activity program to help get your weight and your body fat under control.
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