Читать книгу Clinical Obesity in Adults and Children - Группа авторов - Страница 21

So far, we have only been considering analyses of obesity epidemiology in terms of BMI, but as previously mentioned, Asian physicians have long been concerned by the onset of obesity’s comorbidities at much lower BMIs than in Western Europe or North America. The long‐standing clinical observation that abdominal obesity was particularly hazardous had led to Vague’s identifying decades ago that there was a particular risk if a patient had an android phenotype as distinct from a gynecoid pattern of fat distribution with a small waist/hip (W/H) ratio [25]. The likelihood that abdominal obesity was associated with additional risk was widely accepted, but the definition of what constituted abdominal obesity was uncertain except in terms of a high W/H ratio (>1). The Scottish Royal Colleges of Physicians were preparing a simple guide for general practitioners in 1993 on how to tackle obesity and sought to have the assessment and management summarized on a single page chart which could be placed on a GP’s consulting room table. This necessitated a numerical definition of what normal waist measurements were and what the cut‐offs should be for specifying abdominal obesity. Based on the data from a population survey of adults in the Netherlands, Mike Lean and Jaap Seidel decided to simply take the waist measurements of 94 and 102 cm in men and 80 and 88 cm in women since these values corresponded epidemiologically to BMIs of 25 and 30 in the Dutch population [26]. They also noted that values exceeding these waist circumferences were associated with higher cardiovascular risks. These values were therefore taken as the cut‐off points for abdominal obesity in the Scottish Intercollegiate Guidelines Network (SIGN) guidelines [27] and were then promptly incorporated by the National Institute of Health (NIH) group into their US guidelines for tackling obesity [28] as well as being used in the draft IOTF report for WHO, and then incorporated as the cut‐off points in the report of the first WHO Expert Technical Committee to deal with obesity [5].

Figure 1.1 Obesity prevalences in different regions of the world. Data for males are in the left block of data and females in the right‐hand series. Within each data set, the prevalences for 1980 are on the left and for 2008 on the right.

(Source: Reproduced from Finucane et al. [16].)

The INTERHEART international study later showed that waist size and W/H ratios were better indices of the risk of CHD than BMI [29]. W/H values showed marginally better statistical discrimination probably because higher hip values seem to be protective, perhaps relating to the body’s ability to safely store fat subcutaneously – on the hips. The importance of abdominal obesity as a predictor of morbidity has been shown many times, but the waist/height ratio expressed in metric units with a simple ratio cut‐off of 0.5, rather than hip circumference, seems a better and clinically more practical predictor of disease risk factors, e.g. dyslipidemia, increased blood glucose levels, or higher blood pressures [30] especially in children [31].