by Eileen Swee Lian Goh

Created on: May 04, 2009   Last Updated: June 03, 2009

DEFINITION OF BMI

Developed by a Belgian statistician, Adolphe Quetelet (1796 -1874), BMI stands for Body Mass Index (or Indicator) and is used internationally as an indirect measure of body fat and obesity. It links an individual's weight and height according to the following equation:-

BMI = {Weight (in kilograms)} / {Height (in metres)} / {Height (in metres)},

or, in Imperial Units,

BMI = {Weight (in Pounds)} / {Height (in inches)} / {Height (in inches)} X 703.

BMI RANGES AND INTERPRETATION

BMI scores of less than 18.5 belong to the "Underweight" range. "Normal" or "Healthy" BMI scores fall between 18.5 and 24.9. The "Overweight" range lies between 25 and 29.9, while scores of 30 and above denote "Obesity".

LIMITATIONS OF BMI

The BMI is highly dependent on an individual's weight; hence, in athletes and other individuals with increased weight due to muscle mass and not fat, their BMI scores may give an overestimation of their body fat content, while the reverse is also true for individuals with decreased muscle mass whose BMI scores may reflect an underestimation of their actual body fat content.

In accessing the risks of developing various diseases with obesity, BMI scores are best used together with measurements of waist-to-hip ratios.

IMPACT OF BMI ON HEALTH AND WELL-BEING

Apart from the social stigma associated with obesity in certain cultures, individuals who are overweight or obese have increased risks of:-

A) Diabetes mellitus (DM), due to increased insulin resistance in obesity.

B) Hyperlipidemia, which is essentially raised "bad" cholesterol (LDL) and triglycerides in the blood and decreased blood levels of "good" cholesterol (HDL).

C) High blood pressure or hypertension.

Hyperlipidemia predisposes to atherosclerosis in which cholesterol plaques are deposited along the inner walls of blood vessels, leading to narrowing of affected vessels and, consequently, hypertension.

Atherosclerosis involving the renal arteries can also lead to renal hypertension.

D) Heart disease.

Hypertension and DM are major risk factors for ischemic heart disease (IHD), which ranges in severity from angina to acute myocardial infarction or heart attack. Hypertension also predisposes to congestive heart failure.

Atherosclerosis affecting the coronary artery results in coronary artery disease, which can also lead eventually to IHD due to decreased oxygen supply to the heart.

Even in the absence of hyperlipidemia, hypertension and DM, studies have shown that

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