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Obesity and the metabolic syndrome

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The features of the metabolic syndrome include type 2 diabetes, insulin resistance, hypertension, and dyslipidaemia. It is associated with an increase in risk factors for cardiovascular disease. In the US third National Health and Nutrition Examination Survey (NHANES III) of 1988–94, 7% of overweight, and 29% of obese, adolescents had the metabolic syndrome. Since that survey the prevalence and degree of obesity have increased in the United States. Now researchers in New Haven and Cincinnati (Ram Weiss and colleagues.

) have underlined the problem of the metabolic syndrome in obese children and adolescents.

They studied 490 children and adolescents (mean age 12 years), 195 of whom were severely obese (BMI z score >2.5), 244 moderately obese (z score 2.0 – 2.5), 31 overweight (BMI 85th to 97th centile), and 20 non-obese (BMI < 85th centile). The overweight and non-obese subjects were siblings of obese subjects. Subjects had a standard glucose tolerance test and baseline measurements of blood pressure, plasma lipids, C-reactive protein, interleukin-6, and adiponectin. The metabolic syndrome was defined according to modified national and international criteria, (three or more of: BMI >97th centile, triglyceride >95th centile, HDL cholesterol <5th centile, or impaired glucose tolerance). Insulin resistance was assessed from fasting plasma insulin and glucose using a homeostatic model.

The metabolic syndrome was diagnosed in 39% of moderately obese and 50% of severely obese subjects but in none of the overweight or non-obese siblings. Among obese subjects the risk of the metabolic syndrome increase by 55% for each increase of 0.5 in BMI z score and by 12% for each unit increase in insulin resistance. Increasing obesity was associated with increasing prevalence of impaired glucose tolerance, increasing insulin resistance and systolic blood pressure, and increasing blood concentrations of glucose, insulin, triglycerides, C-reactive protein, and interleukin-6. Concentrations of HDL cholesterol and adiponectin decreased with increasing obesity. All of these changes are associated with increased cardiovascular risk in adult life.

Seventy-seven obese subjects, 34 of whom had the metabolic syndrome at the initial assessment, were followed up after an average of 22 months. Eight had developed type 2 diabetes. Ten of the 34 no longer satisfied criteria for the metabolic syndrome but 16 of 43 subjects who did not have the syndrome initially now satisfied the criteria.

The metabolic syndrome is common among obese children and adolescents and increases in prevalence with increasing obesity. Risk factors for adult cardiovascular disease are already present with obesity at this age.