New Body Mass Index (BMI) Cut-offs for the Diagnosis of Obesity and Comorbidities

The prevalence of overweight and obesity has increased alarmingly in the last decades. Obesity is a serious medical problem because it increases the risk of hypertension, type 2 diabetes mellitus, coronary heart disease, sleep-breathing disorders, and certain forms of cancer. Obesity is defined medically as a state of increased adipose tissue of sufficient magnitude to produce adverse health consequences. The definition of obesity is based on an excess of body fat, not of BMI. However, BMI is the reference used to establish a graded classification of weight relative to height. Although BMI is widely used as a simple surrogate measure of body fat and has been shown to correlate closely with adiposity, it would be more appropriate to determine body fat percentage and to use this value for classification purposes. The present study contemplates the determination of the per cent body fat (by air displacement plethysmography) in more than 5,000 subjects representing the whole BMI range, with the aim of establishing new diagnostic and therapeutic criteria according to the associated comorbidities. The specific objectives are: a) To know the body fat percentage means for normal weight, overweight and obesity for both sexes. b) To know the body fat percentage means for normal weight, overweight and obesity for the different age ranges. c) To analyse the relationship between body fat percentage and BMI values in order to detect misclassified individuals. d) To establish new cut-offs for body fat percentage and the normality ranges according to its relationship with cardiovascular risk factors that could be useful in the diagnosis and therapy of obesity.