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Body Mass Index (BMI), Body Composition and Obesity [Click here to go to BMI Calculator on this page] What is body mass index ? Body mass index (or BMI) is defined as the person’s body weight divided by the square of his or her height. Body mass index may be calculated using the formula below:
Body Mass Index Calculator : Scroll down to the bottom of this page to calculate your body mass index BMI is a crude method to estimate obesity Body Mass Index (BMI) is one of the ways to determine when extra fat accumulation translates into health risks. Body mass index is a measure which takes into account a person’s weight and height to gauge total body fat in adults. The higher the body mass index, the greater the risk of developing additional health problems. The following chart describes the various categories of obesity based on body mass index:
Heart disease, diabetes and high blood pressure are all linked to being overweight and obese. BMI and Mortality Risk As the body mass index and obesity increase, so does the mortality risk. The following figure gives the relationship between body mass index and mortality risk
It is clear from the figure above that the healthy range of body mass index where the mortality is lowest lies somewhere between 20 and 27. Body Mass Index is not the best method But a word of caution! Body mass index does not totally and exclusively describe the health status of a person. The concept of body mass index does not apply at all to athletes and body builders, because, body mass index does not take into account the body composition. Athletes and body builders generally have more muscle and bone mass than fat as compared to general people. To give an example, consider a body builder whose weight is 120 Kg. and whose height is 173 cm. As per the formula given above his body mass index works out to be about 40 which falls in the category of being severely obese. But this is far from truth because the body builder in question has very low fat percentage as compared to a lay person whose body mass index is 40. Waist-to-hip ratio is a better benchmark of risk for health than body mass index The BMI or body mass index is the current standard for healthcare professionals to evaluate body fat. Although BMI may be misleading for certain populations such as athletes, body builders, the elderly, pregnant women, and shorter people, the BMI is still a useful tool for most people. Experts now believe that the waist-to-hip ratio is a better index to evaluate health risks associated with fat on the belly. Men whose waists are larger (more than about 40 inches for the westerners and 35 inches for Asians) are described as being apple-shaped. (The respective measurements for women are 35 inches for westerners and 32 inches for asians) Apple shape bears more risk for health including diabetes, heart disease, high blood pressure. In fact the apple shape is one of the major characteristics of the metabolic syndrome X In a recent study by Salim Yusuf and others of the Population Health Research Institute of McMaster University and Hamilton Health Sciences at Canada has demonstrated that waist-to-hip ratio, (and not the BMI) more accurately demonstrated to be a predictor of heart attack.
SOURCES: Yusuf, S. The Lancet, Nov. 5, 2005; vol 366: pp 1640-1649. Kragelund, C. The Lancet, Nov. 5vol 366: pp 1589-1591. News release, The Lancet. |
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