The prevalence of obesity is increasing in the United States and many other countries, and has now passed smoking as the most preventable cause of morbidity and mortality. Obesity is an excess of adipose tissue that results from a mixture of genetic predisposition, environmental influences (e.g., sedentary lifestyle), and behavioural components (e.g., food as a reward), and it is a chronic, relapsing condition. The rapid increase in obesity prevalence is, however, not due to genetic changes but rather is a societal mismatch between physiology and environment, where food is abundant and exercise is unnecessary. The definition of excess adipose tissue, for the purpose of correlating this to disease outcomes, is through body mass index (BMI), which is calculated as weight (kg)/height (m²). Overweight is a BMI of 25-29.9 kg/m², and obesity is a BMI equal to or greater than 30 kg/m². There is evidence that all-cause mortality is higher in obese people, primarily due to increased cardiovascular disease (CVD) mortality and increased obesity related cancer (colon, breast, uterine, ovarian, renal, and pancreatic) mortality.