disorders of nutrition
Obesity
Introduction
Obesity is a chronic, recurring complex disorder characterized by excess body weight. Obesity is influenced by a combination of factors that includes genetics, hormones, behavior, and the environment. Having the disease of obesity increases the risk of many disorders, such as Diabetes Mellitus (DM) , Increasing activity and reducing caloric intake are important components of treating obesity. Medications and weight-loss (bariatric) surgery are also important for long-term successful treatment for many people with obesity. Losing as little as 5 to 10% of body weight can help lessen weight-related problems, such as diabetes, high blood pressure, and Dyslipidemia . (See also Obesity in Adolescents .) The body mass index (BMI) is used to define overweight and obesity. BMI is weight (in kilograms) divided by height (in meters squared): Overweight is defined as a BMI of 25 to 29.9. Obesity is defined as a BMI of 30 to 39.9. Severe obesity is defined as a BMI of 40 or higher. For people who are of Asian descent and some other ethnic groups, the BMIs that are considered normal and overweight are slightly lower. Definitions for children and adolescents are also different.. BMI does not distinguish between muscle (lean) and fat tissue. Thus, based on BMI alone, some people may be diagnosed with obesity when their percentage of body fat is very low. For example, some people, such as body builders, have a high BMI because they have a large amount of muscle (which weighs more than fat), even though they have very little fat. Such people are not considered to have obesity. Obesity has become increasingly common throughout the world. In the United States, obesity is very common and has nearly doubled since the late 1970s. The national obesity rate for adults between 2017 and 2020 was 41.9%. The national youth obesity rate was 19.7% over this time frame. Also, severe obesity has become more common. Obesity is much easier to prevent than treat. Once people gain excess weight, the body resists losing weight. For example, when people diet or reduce the number of calories they consume, the body compensates by increasing appetite and reducing the number of calories burned during rest. 