The assessment of obesity: methods for measuring body fat and global prevalence of obesity.

Fat is a normal component of the human body that is stored in adipose tissue. Obesity can be defined as a condition of excessive fat accumulation to the extent that health and well-being are affected. Body fat can be determined in vivo in different ways, using rather accurate laboratory techniques or using simple estimation techniques that can also be applied in field conditions. For population studies, the World Health Organization defines cut-off values for obesity based on the body mass index (BMI): weight/height squared (kg/m2). Generally, for adults, if the BMI exceeds 25 kg/m2, a subject is considered to be overweight, and if the BMI exceeds the value of 30 kg/m2, a subject is considered obese. However, the relationship between body fat percentage and BMI differs between ethnic groups, and, as a consequence, cut-off points for overweight and obesity based on BMI will have to be ethnicity specific. This means that, in some populations, the cut-off points could be lower or higher than the recommended figures. Adapting cut-off point values will have important consequences for prevalence data in some countries as the prevalence of obesity will dramatically increase or decrease. The prevalence of obesity, in children as well as in adults, is high in many countries all over the world and is rising. Given the impact of obesity on health, this is a public health issue that needs to be addressed seriously.