As excess body weight is such a common condition, a simple, easily obtainable measure of body ‘fatness’ is necessary to quickly assess whether an individual is overweight. As such, the Body Mass Index (BMI) is widely accepted as the most appropriate measure of body fat, with a BMI threshold of 25 kg/m2 set for overweight, and a threshold of 30 kg/m2 set for obesity (you can calculate your own BMI in the right hand column here). However, a recent systematic review suggests that the use of BMI fails to identify half of individuals who have an excess of body fat.

This has led to the coining of a new term, called Normal Weight Obesity or NWO. This refers to individuals who fall into the normal weight zone for BMI, but who have an excess percentage of body fat. NWO individuals have an increased risk of metabolic syndrome, high cholesterol, and high blood pressure. Of great concern, a recent study has demonstrated for the first time that NWO women are at a 2.2-fold increased risk of death from cardiovascular disease.

The question is, how can we detect NWO? Body composition and body fat percent can be assessed by a number of different methods. The simplest of these methods are measures of skin fold thickness (where your skin gets pinched gently between calipers) and bioimpedance (scales that send electrical currents through your body). A more accurate measure is a DEXA scan (pictured above), which is the same machine used for detection of osteoporosis. DEXA scans are not covered by Canadian health care for assessment of body fat, though some insurance providers in the US are covering them for body composition assessments (the cost is about $100 USD). The criteria to define NWO is debated as well; the most accepted definition is that put forth by the World Health Organization: >25% body fat for men, and >35% body fat for women.

For the time being, bioimpendance scales are probably the most accessible method for finding out your own body composition. Many doctors’ offices have these, or alternatively, they can be purchased for personal use. Although they are not exceptionally accurate, they may be of value to follow your change in body fat percent with time, as you engage in a dietary weight loss or exercise program.

The discovery of NWO teaches us once again about the importance of body fat as a metabolic organ, and the importance of leading a healthy, active lifestyle to not only maintain ‘normal’ weight, but also to keep lots of lean, metabolically healthy muscle tissue on board.

Dr. Sue © 2010