The Body Mass Index or BMI is a method of classifying whether an individual is overweight, underweight, obese or normal weight based only on their height and weight and does not use gender specific information.
The BMI does not make a distinction between fat and muscle .A person with a lot of muscle (such as an athlete) may have a BMI in the unhealthy range, but still be healthy and have little risk of developing diabetes or having a heart attack. BMI also may not accurately reflect body fatness in people who are under 5 feet and in older people, who tend to lose muscle mass as they age.
BMI cutoff points are a guide for overweight and obesity and are useful for comparative purposes across populations and over time; however, the health risks associated with overweight and obesity are on a continuum and do not necessarily correspond to rigid cutoff points. For example, an overweight individual with a BMI of 29 does not acquire additional health consequences associated with obesity simply by crossing the BMI threshold > 30. However, health risks generally increase with increasing BMI.
Excess weight, as measured by BMI, is not the only risk to your health. So is the location of fat on your body. If you carry fat mainly around your waist, you are more likely to develop health problems than if you carry fat mainly in your hips and thighs. This is true even if your BMI falls within the normal range.. Women with a waist measurement of more than 35 inches or men with a waist measurement of more than 40 inches may have a higher disease risk than people with smaller waist measurements because of where their fat lies.
Extra weight can put you at higher risk for these health problems – type 2 diabetes (high blood sugar), high blood pressure, heart disease and stroke, some types of cancer, sleep apnea (when breathing stops for short periods during sleep), osteoarthritis (wearing away of the joints), gallbladder disease, liver disease and irregular menstrual periods.