Definitions, Classification, and Epidemiology of Obesity

Obesity is now recognized as a chronic or non-communicable disease. Recent research has clarified the physiology of weight regulation, the pathophysiology that leads to unwanted weight gain and maintenance of the obese state even when reasonable attempts in lifestyle improvement are made, and the adverse health consequences of generalized and central obesity. While more sensitive and specific imaging methods to quantify body composition are available, most office-based practitioners will need measure only height, weight, and waist circumference. With these, a patient’s risk for obesity-related co-morbidities such as type 2 diabetes mellitus and cardiovascular disease can be estimated and appropriate treatment plans and goals established. Within the United States, prevalence rates for generalized obesity (BMI > 30 kg/m2), extreme obesity (BMI > 40 kg/m2), and central obesity are continuing to rise with peak obesity rates occurring in the 5th-7thdecades. Women have more generalized obesity but less central obesity than men, and obesity disproportionately affects US minorities. Of concern are increases in obesity rates in youth (ages 2-19 years) in the US as well as around the globe. This trend will likely continue to fuel the global obesity epidemic for decades to come, worsening population health, creating infrastructural challenges as countries attempt to meet the additional health-care demands, and greatly increasing health-care expenditures world-wide. Beyond individual weight management, societal and economic innovations will be necessary that focus on strategies to prevent further increases in overweight and obesity rates. For complete coverage of all related areas of Endocrinology, please visit our on-line FREE web-text, WWW.ENDOTEXT.ORG.