How common is obesity?
Obesity is simply defined as the excess of body fat. The degree of body fat relative to weight is calculated by the body mass index (BMI; kg/m 2 ). Overweight is a BMI 25.0 to 29.9 kg/m 2 ; obesity is a BMI ≥ 30 kg/m 2 ; morbid obesity is a BMI ≥ 40 kg/m 2 .
Increasing BMI correlates with increasing health issues, including diabetes mellitus, hypertension, sleep apnea and Pickwickian syndrome, asthma, coronary artery disease, cardiomyopathy, gastroesophageal reflux disease, degenerative joint disease, hyperlipidemia, fatty liver (hepatic steatosis and nonalcoholic steatohepatitis), gout, urinary incontinence, gallbladder disease, psychological disorders, menstrual irregularities, infertility, and certain cancers (endometrial, colon, breast, and kidney).
Most importantly, a BMI > 40 kg/m 2 increases the risk of death from all causes twofold. Approximately 127 million adults (64%) in the United States are considered overweight, and 93 million adults (39.8%) are considered obese. Nearly 18.5% of children and adolescents are obese, with wide variation in certain regions.