Body mass index (BMI) was introduced in the 19th century as a measure of weight relative to height. Before the late 20th century, overweight and obesity were not considered a population-wide health risk, but the advent of new weight loss drugs in the 1990s accelerated the medicalization of BMI. A BMI category labeled obesity was adopted in 1997 by a World Health Organization consultation and subsequently by the US government. Language in the National Coverage Determinations Manual stating that "obesity itself cannot be considered an illness" was removed in 2004, allowing reimbursement for weight loss treatments. In 2013, the American Medical Association declared obesity to be a disease. Yet the focus on BMI categories and on weight loss has yielded few health benefits and contributes to weight-related discrimination and other potential harms.An Important Clinical Problem? Dramatic statements about the health risks of obesity are common today. The opening lines of a recent article read: "Obesity is the most prevalent chronic disease worldwide, affecting approximately 650 million adults. Excess adiposity and its numerous complications, including cardiovascular disease and type 2 diabetes, impose a considerable economic burden and constitute major contributors to global morbidity and mortality." 1 Such assertions are a recent development. According to the Institute of Medicine, "Prior to the late 20th century, overweight and obesity were not considered a population wide health risk." 2 Body weight was often considered as more of a cosmetic and social issue than an important medical concern. 3 A 1969 study found that patients and physicians did not view body weight and weight loss as salient medical problems and considered deviations from weight standards to be almost meaningless. 4 Prior to 2004, the National Coverage Determinations Manual stated bluntly that "obesity itself cannot be considered an illness," 5 and treatment for obesity was not covered by Medicare. 5 The costs of weight loss as a treatment for obesity were not allowed as a medical deduction for tax purposes until 2002. 6 Until the 2010s, in most doctor visits, BMI was not calculated. 7