Obesity is an excessive accumulation of body fat that confers a variety of health risks, including diabetes, cardiovascular disorders, arthritis, and some types of cancerous tumors. The risk to health is determined by the amount of body fat, the distribution of body fat, and the presence of other risk factors. Obesity has long been considered to be a public health problem, but a significant step was taken when the American Medical Association, the largest physician organization in the United States, officially classified obesity as a disease that requires a range of medical interventions to advance treatment and prevention. In particular, because more than one-third of adults and approximately one-fifth of children in the United States are recognized as obese, the designation of obesity as a disease is expected to prompt the medical community and public policy makers to support further interventions and research into obesity prevention and treatment. See also: Diabetes; Disease; Epidemic of obesity; Obesity; Public health
Obesity can be defined in terms of a person’s body mass index (BMI). The BMI is a ratio of an individual’s weight in kg to height in m2. Studies have found that BMI relates to levels of body fat (adipose tissue), adipokines (hormones and cytokines that are secreted by fat tissue), energy metabolism, and obesity-related health consequences. An individual with a BMI of more than 30 is categorized as being obese (note that the BMI for an individual of “normal” weight is 18.5–24.9). See also: Adipose tissue; CTRPs: novel adipokines; Leptin
The increasing prevalence of obesity in today’s society is of great concern. Genetic factors can contribute to the likelihood of potential weight gains in an individual, but people’s genetic makeup cannot explain why obesity has increased drastically in various populations over a span of decades. Factors related to lifestyle and diet must therefore be playing important roles. For example, rapid advances and improvements in technology have led to huge reductions in individuals’ levels of physical activity. People are also consuming far more calories than they did in previous years, and the increased marketing of high-calorie, high-fat, and high-sugar foods, particularly to children, has led to troublesome public health effects. See also: Dietary fructose and the physiology of body weight regulation; Triglyceride (triacylglycerol)
The most typical way to treat and prevent obesity involves some amount of dietary change. Regimens that combine diet and exercise are most effective in treating and preventing obesity. Prescription weight-loss medications and weight-loss (bariatric) surgery may be necessary interventions in difficult cases. See also: Food; Nutrition
