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Chapter 27: Obesity and Cardiovascular Disease

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What approximate proportion of the adult population worldwide is overweight or obese?

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A. 20%

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B. 30%

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C. 40%

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D. 50%

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E. 60%

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The answer is C. (Hurst’s The Heart, 14th Edition, Chap. 27) Prevalence rates of obesity have increased sharply worldwide over the past 30 years.1 Worldwide, the proportion of adults with a BMI of 25 kg/m2 or greater increased between 1980 and 2013 from 28.8% to 36.9% in men, and from 29.8% to 38.0% in women.2 Prevalence has increased substantially in children and adolescents in developed countries, to the point where 23.8% of boys and 22.6% of girls were overweight or obese in 2013.2 In the United States, data from the National Health and Nutrition Examination Survey (NHANES) show that roughly two out of three US adults are overweight or obese, more than one-third are obese, and 17% of children are obese.3,4 This has created a global health crisis with a profound impact on morbidity, mortality, and health care costs largely attributable to weight-related complications.

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What proportion of a person’s risk for obesity is attributable to genetic factors?

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A. < 10%

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B. 10% to 20%

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C. 30% to 40%

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D. 50% to 60%

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E. > 60%

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The answer is D. (Hurst’s The Heart, 14th Edition, Chap. 27) Like many other chronic diseases, genetic factors constitute a substantial component of disease risk5 that can explain 50% to 60% of individual variation in body weight in monozygotic/dizygotic twin studies. Monogenic forms of the disease are rare, such as in families with leptin or leptin receptor mutations or deletion of the SNORD116 gene cluster in patients with Prader–Willi syndrome. Susceptibility to obesity in most people results from the inheritance of multiple genes, with each allele conferring a very small relative risk for the disease. Genomewide association studies have identified more than 100 susceptibility loci for obesity.6 Particularly strong association signals have been detected for the fat mass- and obesity-associated gene (FTO) and the melanocortin-4 receptor (MC4R) gene, but even these variants confer odds for obesity of less than 1.7.7,8 The multiple susceptibility genes interact with each other and with the environment, behavior, and biological factors to produce individual variation in the risks of obesity. The development of excess adiposity is a complex process; however, those individuals who inherit larger subsets of obesity susceptibility genes will ...

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