Underweight Normal Overweight Obesity Class Obesity Class II Obesity, extreme
comparisons of weight between two individuals in a population difficult. The BMI is a concept of weight that estimates the degree of body fat independent of height, gender, or ethnicity. Since increasing BMI is associated with increasing risks for comorbidities, every physician should be familiar with the common cut-off points. These are presented in Table 6.1.
It is often assumed that obesity equals insulin resistance, since overweight people tend to become more insulin sensitive with weight loss.5 However, results from the European Group for the Study of Insulin Resistance have shown that only 25 percent of people who are overweight had evidence of insulin resistance.6 Epidemiological evidence suggests that persons in the upper tertile of insulin resistance (measured by insulin-mediated glucose disposal) are at a statistically, significantly increased risk for developing type 2 diabetes, coronary heart disease, or hypertension.7,8
Recently, several well-designed clinical trials suggest that changes in lifestyle can prevent the onset of diabetes. In the Finnish Study, 522 obese (mean BMI 31 kg/m2) subjects were randomized to receive brief or individualized lifestyle instruction. After 3.2 years, there was a 58 percent relative reduction in the incidence of diabetes in the intervention group with individualized instruction.9 Diabetes Prevention Program is a multicenter, three-arm trial that randomized 3234 people at risk for diabetes to either a placebo pill or metformin plus minimal diet and exercise education (yearly individual sessions with handouts), or an intensive lifestyle intervention (diet, exercise, and behavioral education in a 16-lesson, 24-week curriculum, followed by monthly sessions, with both individual and group sessions).10 The intensive lifestyle group lost more weight (-5.6 kg versus -2.1 kg versus 0.1 kg) and had lower diabetes incidence (14.4 percent versus 21.7 percent versus 28.9 percent) than the metformin group and the control group, respectively. Interestingly, these results were seen even though only 50 percent of participants in the intensive group achieved the goal of 7 percent or more weight loss at 24 weeks, and only 58 percent were adherent to the exercise recommendation (150 minutes per week) at the most recent visit (mean follow-up 2.8 years). The intensive group successfully reduced energy intake by an average of 150-200 Kcal per day compared with the
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