Several criteria have been suggested to measure obesity but a few simplified objective methods for its assessment are now widely acceptable worldwide A person is obese when a he or she is 20% above the recommended weight for his or her height and build. Another direct method for estimation of body fats include Densitometery which simply entails weighing under water and uses the basic principle that fat and other body tissues have different density, and hence the actual fat content can be calculated. Convenient methods used in clinics are as follows:
Skin fold thickness
Ordinary calipers can be used to measure skin fold thickness over the biceps, triceps or below the shoulder and standard charts are used to assess the degree of obesity.
Body mass index (BMI)
This is a quick, easy and reliable method. It uses the ratio of weight in kgs divided by the square of height in meters, i.e., W/H2 for example for someone weighing 70 kgs. and a height of 175 cms. Body Mass Index (BMI) will be 70/(1.75)2 = 23. BMI of 25 is taken as upper limit of normal, and a span of 25-29.9 as overweight. Values above 30 is obese. In terms of disease and mortality, scientists have categorized BMI under four categories.
|BMI Relative Index|
Ratio of the waist measured at the narrowest part between the rib cage and hips divided by measurement of hips at the widest part determines a simple but useful ratio. Scientists have enough evidence that a ratio higher than 1.0 for men and 0.9 for women are associated with high risks of getting diabetes and cardiovascular morbidity.
Standard tables of height and weight in correlation to the risk of mortality at different ages are convenient. These are derived from various sources such as life insurance data and nationwide disease prevalence. However they have several limitations as they take into account only a cross sections of the population.
The Most useful Criteria
For a quick assessment of obesity and related risk, the BMI and waist/hip ratio are the best since enough data is now available nationwide and worldwide.