Time to redefine body mass index categories in chronic diseases? Spotlight on obesity paradox

Obesity is a complex condition classically characterised by excessive body fat accumulation and represents one of the most important public health problems worldwide. Although several epidemiological studies have shown that elevated BMI is associated with higher morbidity, and with increased rate of death from all causes and from cardiovascular disease, accumulating evidence suggests that being overweight or obese may be protective (the so-called obesity paradox), at least in chronic diseases. These observations, not only question the validity of the BMI system, but also raise the intriguing question of whether we should redefine what the normal range of BMI is in individuals suffering from a chronic disease. In the present article, we review the available information on the association between elevated BMI and increased morbidity and mortality including obesity-related paradoxes, explore key aspects of the role and limitations of BMI as a measure of increased adiposity and outline potential solutions to address the current controversies regarding the impact of obesity on human health.