This chapter discusses obesity and how it impacts on cardiovascular health and disease. Global prevalence of obesity has increased considerably over the past 30 years, impacting profoundly on morbidity, mortality, and healthcare costs. In the majority of individuals, susceptibility to this chronic disease depends on the inheritance of multiple genes, each conferring a very small relative risk; monogenic forms of obesity are rare. Lifestyle factors—including dietary patterns, physical activity, stress, sleep hygiene, and circadian rhythms—also have important roles in the development of obesity. Direct effects of the excess adipose tissue on other organ systems contribute to increased cardiovascular risk in obese individuals (see accompanying Hurst's Central Illustration). The adverse health effects of excess adiposity manifest by the development of weight-related complications and the emergence of risk factors for those complications. In obese individuals, pathophysiological adaptations (such as in the hypothalamic regulation of appetite) make it challenging to reduce adiposity and maintain any weight loss. Recommended therapeutic strategies for obese individuals involve lifestyle intervention (including dietary changes, increases in physical activity, and behavioural therapy), pharmacotherapy, and bariatric surgery. Weight loss reduces risk of type 2 diabetes mellitus, lowers blood pressure, and results in lower triglyceride and LDL cholesterol levels and higher HDL cholesterol levels.
Hurst's Central Illustration: Pathophysiology of Obesity and Consequential Cardiovascular Disease
Pathophysiology of obesity and consequential cardiovascular disease. Genetic, environmental, and behavioural factors all contribute to obesity. Obesity causes changes to the hypothalamic regulation of appetite that make it challenging to reduce adiposity and maintain any weight loss, and thereby promote obesity. Obesity also promotes the behavioural factors that promote obesity; for example, by causing psychological changes to food preferences (toward foods with greater caloric density with high fat and sugar content), by making physical activity more difficult, and by increasing the risk of sleep apnea and thereby impacting negatively on sleep hygiene. Obesity is also associated with alterations in adiposity-accumulation of intra-abdominal fat and of lipids within muscles and liver cells-that result in insulin resistance and dysregulated secretion of adipokines, which lead to diabetes mellitus and the metabolic syndrome, and can eventually result in the development of cardiovascular disease.
Prevalence of obesity has increased sharply worldwide over the past 30 years.1 Globally, the proportion of adults with a body mass index (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,...