With studies revealing new insights into body weight and health issues, people no longer talk about body weight by itself. For quite some time, the body mass index or BMI has been the accepted form of determining the ideal weight of a person, and the deviation from this ideal weight that needs to be corrected. This is the weight of a person expressed as a ratio of his height.
Simply spoken, the BMI is expressed as the body weight in kgs/the height in sq. meters.
People with elevated BMIs have been known to be more susceptible to diabetes mellitus, cancer, hypertension and hypercholesterolemia. Research also reveals that people with higher BMIs have higher incidences of premature death. It is generally recommended that a person’s BMI should remain in the range of 18.5 – 24.9. People having lower BMIs are said to be underweight, whereas those having higher (25-29.9) are overweight. People with BMIs greater than 30 are said to be obese and should be seriously concerned about weight loss and lifestyle control.
However, recently, experts have started pointing out some limitations of the BMI measurement as an ideal tool to determine healthy weight. It does not distinguish between fat mass and fat free mass, which may yield incorrect interpretations. Fat free mass, that is, lean muscle, is actually desirable as it burns fat. People with more lean tissue may have a higher BMI and yet be healthier compared to people with higher fat percentage and a lower BMI.
Furthermore, recent research points out that the location of the body fat is important in deciding propensity towards developing a disease. BMI does not give any indication of about the location of body fat in an overweight or obese person. Recent developments suggest that the body fat expressed as a percentage of total body weight is a better indicator of health. A person with low body fat is deemed healthier than a person having the right BMI but more fat.
For this purpose, the body fat is measured in several ways. Commonly, skin fold calipers ‘pinch’ a section of the flesh to determine the fat in it. Another method, called Bioelectrical Impedance (BEI), measures body fat electronically.
However, both the above methods should not be employed immediately after exercising. The skin fold caliper method requires an expert to measure the different levels of fat in various areas of the body. The hydration level of the body greatly affects the fat calculated through the BEI method.
Underwater weighing, which involves submerging the person in water and calculating the fat from the volume of displaced water is another effective method of measuring body fat. However, most people do not have access to the equipment for this.
According to experts, normal females have body fat levels of 22-25%, while normal males have 15-18%. Lean and athletic structures have less than the normal level of body fat. Women having 29-35% body fat are considered over-weight, whereas males are labeled over-weight if their body fat is more than 20%. It is generally recommended that people retain their body fat levels as close as possible to ‘lean’ structures.
Proponents of the body fat theory also suggest that the location of the body fat is vital in determining risk factors. For example, excess deep abdominal fat which accumulates around the vital organs has been linked to diabetes, heart disease etc. Fat around the hips and thighs is considered relatively less risky. The measurement of the waist circumference is a good indicator of fat related disease propensity.
As is evident, body fat measurement is a more efficient method of calculating the healthy body weight compared to the BMI. However, common body fat measurement methods have a margin of error of 1-4%, and are not easily accessible by everybody. BMI, on the other hand, is a simple mathematical calculation which can be used by anybody.