Obesity: Understanding Obesity.

Obesity is a chronic, multifactorial disease linked to multiple chronic conditions. Rates of obesity are increasing in the United States and worldwide. Although body mass index is an imperfect measure of body mass, it remains the most widely used metric. Other available measures of body and fat mass include anthropometric measurements, bioelectrical impedance analysis, and imaging. Factors implicated in increasing obesity rates in the United States include diets with ultra-processed foods; decreased levels of physical activity; iatrogenic effects from commonly prescribed drugs with weight gain potential; and environmental-genetic factors, such as genetic predisposition, epigenetics, and composition of the gut microbiome. Rates of obesity among children also have been increasing. The U.S. Preventive Services Task Force recommends screening of all children older than 6 years for obesity. For elderly patients with obesity, the decision to pursue weight loss management should include consideration of the functional limitations and/or metabolic complications of the patient.