Body Mass, also known as Body Mass Index (BMI) is a number calculated from a person's weight and height and is a helpful tool in determining risk levels for health problems. Instead of relying simply on weight, BMI is now popularly used to determine what a healthy weight is. It is determined by dividing your weight in kilograms by the square of your height in meters (see References). There are lots of online calculators that will save you the headache.
A person that is at a healthy weight will have a BMI of 24 or less. For example, a woman who is 5 feet, 4 inches tall and weighs 125 lbs. has a BMI of 21.5, which is considered to be healthy.
A BMI of 25 to 29.9 is considered overweight, and a BMI of 30 or higher is considered obese. So if the same 5-foot, 4-inch woman weighed 165 lbs., she would be overweight with a BMI of 28.4. And if that same woman weighed 185 lbs., she would be considered obese with a BMI of 31.8.
Lean Body Mass
The BMI calculations do not consider lean body mass. Muscle weighs more than fat, so if you have a lot of muscle mass, BMI will not provide an accurate profile of your weight and health risks. Accuracy will come with a body composition measurement that determines the percentage of body fat. This can be done with a hand-held device or by measuring skin folds with a special tool.
Numerous health risks are associated with being overweight, and as BMI rises above 30, those risks increase dramatically. Heart disease, diabetes, cancer, heart attack, high cholesterol, and high blood pressure are among the health issues that overweight people are at a higher risk of.
How to Change BMI
If you want to lower your BMI, the answer is in diet and exercise. Eat a diet that is low in fat and sugar while high in fiber and vitamins. Be active for 30 to 60 minutes per day--this may even mean that you go for a walk on your lunch break or do jumping jacks in front of the television. Of course, the more completely you dedicate yourself to a healthy lifestyle, the quicker you will see the results in your BMI and your overall health.
Before starting any diet or exercise plan in hopes of reducing your BMI, talk to your doctor about what sort of program will be the most successful for you.