Physical health can be measured (with certain exceptions) through the appropriateness of a person's weight to his height; where the body weight refers to the measure of one's heaviness and the height is the measure of his tallness. For instance, a woman measuring 5 ft high (1.52 m), with a medium body frame should weigh between 103 lbs to 115 lbs (46.72 kg to 52.16 kg) to be considered healthy.

Another example: a man standing 5 ft 8 in (1.72 m) tall, with a large body frame is healthy if he is weighing between 144 lbs to 163 lbs (65.32 kg to 73.94 kg). Otherwise, if their weight is lower than the desired body weight for their height, they are considered underweight. And if, in turn, their weight is higher than the desired body weight for their height, they are said to be overweight.

Body Mass Index is an indicator of surplus body fat and has since replaced the height-weight charts as mentioned in the above examples. It is a mathematical ratio of height to weight that is used to determine body composition (or body fat percentage) to assess a person's level of health risk. Calculating BMI is as follows:

BMI = Weight (in kg) divided by Height (in m)2 or
BMI = Weight (in lbs) x 700 divided by Height (in inches)2

For example, the calculation for someone weighing 80 kg (176 lbs) and 1.60 m (63 in) tall is:

BMI = 80 divided by 160 squared = 31.2 or
BMI = 176 x 700 divided by 63 squared = 31.1

People with a BMI of 25.1 to 29.9 are considered overweight, and people with a BMI of 30 or above are considered obese. Thus, from the example above, a person weighing 80 kg and is 1.60 m tall is obese. A high BMI assumes a higher percentage of body fat, which places a person at greater risk for developing chronic diseases and other serious illnesses.

Body weight categories according to BMI

 BMI               Weight Category 19 and under      Underweight 20-25             Normal (Healthy) 26-29             Overweight 30 and above      Obese

However, for some people, the BMI is not a reliable indication of health. A highly muscled individual who is very fit and healthy may have a somewhat heavy body weight because muscles pack on a lot of pounds. This person may have a high BMI that improperly puts him or her in the overweight or obese categories. Likewise, thin individuals who have a low body weight with very little muscle and a higher percentage of fat may have a normal BMI, which would be an incorrect indication of healthiness.

If you are overweight or obese according to the calculations shown here it is imperative that you undertake a weight loss and fitness program and start bringing that weight down. Remember that for every 10 pounds that you are over your ideal weight, the risks to your health increase and for every 10 pounds that you lose bringing you closer to your ideal weight, the risks to your health decrease.