Category BMI (kg/m2) Underweight 2 but BMI measures are typically used and written without units. :BMI provides a significantly more accurate representation of body fat content than simply measuring a person's weight. It is only moderately correlated with both body fat percentage and body fat mass (R2 of 0.68). It does not take into account certain factors such as pregnancy or bodybuilding; however, the BMI is an accurate reflection of fat percentage in the majority of the adult population. *Body volume index :The body volume index (BVI) was devised in 2000 as a computer, rather than manual, measurement of the human body for obesity and an alternative to the BMI :BVI uses 3D software to create an accurate image of a person so BVI can differentiate between people with the same BMI rating, but who have a different shape and different weight distribution. :BVI measures where a person's weight and the fat are located on the body, rather than total weight or total fat content and places emphasis on the weight carried around the abdomen, commonly known as central obesity. There has been an acceptance in recent years that abdominal fat and weight around the abdomen constitute a greater health risk. *Simple weighing :A person's weight is measured and compared to an estimated ideal weight. This is the easiest and most common method, but by far the least accurate, as it only measures one quantity (weight) and often does not take into account many factors such as height, body type, and relative amount of muscle mass. *Skinfold calipers or "pinch test" :The skin at several specific points on the body is pinched and the thickness of the resulting fold is measured. This measures the thickness of the layers of fat located under the skin, from which a general measurement of total amount of fat in the body is calculated. This method can be reasonably accurate for many people, but it assumes particular fat distribution patterns over the body—which may not apply to all individuals, and does not account for fat deposits not directly under the skin. Also, as the measurement and analysis generally involves a high degree of practice and interpretation, an accurate result requires that a professional perform it. It cannot generally be done by patients themselves. *Bioelectrical impedance analysis :A small electric current is passed through the body to measure its electrical resistance. As fat and muscle conduct electricity differently, this method can provide a direct measurement of the body fat percentage, in relation to muscle mass. In the past, this technique could only be performed reliably by trained professionals with specialized equipment, but it is now possible to buy home testing kits that let people do this themselves with a minimum of training. Despite the improved simplicity of this process over the years, however, a number of factors can affect the results, including hydration and body temperature, so it still needs some care when taking the test to ensure that the results are accurate. *Hydrostatic weighing :Considered one of the more accurate methods of measuring body fat, this technique involves complete submersion of a person in water, with special equipment to measure the person's weight while submerged. This weight is then compared with "dry weight" as recorded outside the water to determine overall body density. As fat is less dense than muscle, careful application of this technique can provide a reasonably close estimate of fat content in the body. This technique does, however, require expensive specialized equipment and trained professionals to administer it properly. *Dual-energy X-ray absorptiometry (DEXA) :Originally developed to measure bone density, DEXA imaging is also used to precisely determine body fat content by using the density of various body tissues to identify which portions of the body are fat. This test is generally considered very accurate, but requires a great deal of expensive medical equipment and trained professionals to perform. The most common method for discussing this subject and the one used primarily by researchers and advisory institutions is BMI. Definitions of what is considered<unk>  vary by ethnicity. The current definition proposed by the US National Institutes of Health (NIH) and the World Health Organization (WHO) designates whites, Hispanics and blacks with a BMI of 25 or more as<unk> . For Asians,<unk>  is a BMI between 23 and 29.9 and obesity for all groups is a BMI of 30 or more. BMI, however, does not account extremes of muscle mass, some rare genetic factors, the very young, and a few other individual variations. Thus it is possible for an individuals with a BMI of less than 25 to have excess body fat, while others may have a BMI that is significantly higher without falling into this category. Some of the above methods for determining body fat are more accurate than BMI but are less convenient to measure. If an individual is<unk>  and has excess body fat it can create or lead to health risks. Reports are surfacing, however, that being mildly<unk>  to slightly obese – BMI being between 24 and 31.9 – may be actually beneficial and that people with a BMI between 24 and 31.9 could actually live longer than normal weight or underweight persons.
Overweight
Underweight
Obesity
Abdominal obesity
Body mass index
Worried well 
Normal weight obesity
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