There are a number of methods to measure if an individual is obese or overweight. Measurements of Body Fat, Body Mass Index, Weight-for-height Chart are the prominent methods to obesity and overweight measurement. These measurement systems are one derivatives of mathematical calculation in relation to body height, weight, body fat and others. Lets have a look each of the methods.
Body Mass Index:
BMI is the most used formula to measure obesity and overweight. It is easy to caculate and most reaserchers and professionals use it to measure and define overweight and obesity. BMI is a direct calculation based on height and weight of our body. The mathematical formula is: kg/m2 that is weight/height2.
If you want to measure your BMI using pounds and inches, just multiply your weight in pounds by 704.5 according to National Institutes of Health or multiply it by 700 according to American Dietetic Association and divide the weight by inches and then the result with inches.
The BMI calculation for overweight is a BMI of 25-29.9 kg/m2, and obesity is a BMI of 30 kg/m2 or greater. The overweight people are not obese; body builders and athletes may have more muscles and may be overweight but they are not obese. But the obese are certainly overweight. Defining overweight as a BMI of 25 or greater is consistent.
Source: Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, National Institutes of Health, National Heart, Lung, and Blood Institute, June 1998.
BMI Classification
< 18.5 underweight
18.5–24.9 normal weight
25.0–29.9 overweight
30.0–34. class I obesity
35.0–39.9 class II obesity
>= 40.0 class III obesity
Calculating BMI is simple but it has some limitations. I stated one of them above that body builder and athelets may be overweight according to BMI when they are healthy and fit. People who has lost muscle mass may be in the healthy weight category even they have reduced nutritional reserves.
Measurements of Body Fat:
Historically this method is to weigh a person underwater, but the process is limited to laboratory equipment.
The professionals now use a simpler method to measure body fat. They do this including bioelectrical impedance analysis (BIA) and skinfold thickness measurements. Skinfold thicknesses are a measurement of specific fat called subcutaneous. The results eventually varies when measured by different examiners.
A harmless amount of an electrical current is sent through the body to measure body fat using BIA. This method reflects the total amount of water in the body. The percentage of body water are used to translate itself into an indirect estimate of body fat and lean body mass. In this process, to acheive the best readings the individual should fast for at least 4 hours and lie down for at least several minutes prior to testing. BMI is not useful for tracking short-term changes in body fat brought about by diet or exercise.
Weight-for-height Chart:
This chart usually gives a range of acceptable weights for a person of a given height. There are many versions of weight-for-height charts exist, some showing different acceptable weight ranges for men and women. So doctors and health workers are often confused over which chart is the best to use.
