Body mass index and weight change: the sixth vital sign.

Determining the heart rate, breathing rate, temperature and blood pressure is an essential and fundamental component of western medicine and of the interaction between health care provider and patient. These physiological parameters are easily measured by physical examination or with a diagnostic device. They are normally maintained within a physiological range by homeostatic feedback systems that have powerful compensatory capabilities. Measurements that exceed or drop below a threshold indicate an underlying pathology and are often associated with increased morbidity and mortality. Furthermore, they may serve as a diagnostic criterion, a prognostic factor, and/or as an indication to initiate treatment. In this brief article, we intend to show that body weight/body mass index (weight/height 2 in kg/m 2) is also a vital sign. Body weight regulation In adults, body weight is efficiently maintained at a set point. Energy intake and expenditure are regulated by the nervous and hormonal systems, including peptides from the gastrointestinal tract, pancreas and adipose tissue. These modulate multi-level physiological processes from motivation to mitochondrial function in order to match energy intake to energy expenditure. It has been calculated that the accuracy of matching energy intake and expenditure over one year is more than 95.5% in adults [1]. The finding of a BMI beyond the 20–30 range or of significant weight loss in a short period indicates a significant deviation in energy balance and has detrimental health implications. Epidemiology and pathophysiology of BMI variations and weight loss Excess weight gain in children and adults is increasingly prevalent worldwide. A large international study found 24% of men and 27% of women to be clinically obese, i.e., having a BMI ≥ 30, although national and ethnic variations exist [2]. Obesity predisposes to type 2 diabetes and atherosclerosis-related disease [3] and is associated with an increased long-term risk of premature death secondary to these disorders and certain cancers BMI = body mass index [4,5]. These deleterious consequences of excessive weight gain are not due to the physical characteristics of triglycerides and adipose tissue, but rather to the spillover of free fatty acids and inflammatory mediators from the expanded adipose tissue. This leads to insulin resistance, dyslipidemia, non-alcoholic fatty liver disease and atherosclerosis. The intra-abdominal fatty deposit is the leading culprit behind the systemic effect of obesity, probably due to its propensity to attract macrophages, its resistance to insulin's inhibitory effect on lipolysis, its prominent blood supply and its venous drainage to …