Background: Most cases of overweight and obesity are caused by positive imbalance between voluntary calorie intake and calorie expenditure. Excess intake of calories in industrialized countries is influenced by social habits often introduced during childhood, easy access to food, intentional appetite stimulation, seductive commercial advertising for obesogenic food products, and genes. Decreased calorie expenditure is influenced by personal life style, physical occupational work, industrial automation, sedentary habits, prolonged television viewing, computer usage. Obesity caused by personal life style is not generally viewed as a disease and is rarely caused by known hormonal abnormalities, although often referred to health institutions for assistance with life style changes and exclusion of rare underlying diseases.

Symptoms: Overweight and obesity increase the risk of heart disease, hypertension, vascular disease, arthrosis, gallbladder disease, sleep apnea, and risk of death from heart disease. The prevalence of type 2 diabetes among people in the UK above age 18 with a BMI of 20-25 is 2-4 %, among people with a BMI of 25-30 it is 4-6%, and among people with a BMI above 30 it is 14-16%. In Sweden, 72% of the population have a body weight that statistically shortens their life expectancy.

Diagnosis: Overweight is defined by a BMI (body mass index: kg body weight/m2 body height) between 25 and 30 and obesity by a BMI above 30. The prevalence of overweight in Sweden is 53 % of the adult population. The prevalence of obesity in Sweden is 19 % of the adult population (2013). Excess fat will often be deposited between the intestines and will in combination with weak muscles of the abdominal wall cause an increase in waist circumference particularly in elderly people (risk of permanent disease is increased in men with a waist circumference above 102 cm, and in women above 88 cm).

Treatment: Both overweight and obesity are most effectively treated by restriction of calorie intake. However, that is difficult for most people, primarily because of the effects of habitual appetite. Restriction of caloric intake requires a detailed diary of the amount of all food and its calorie content as well as of physical activity (apps are available). Self-discipline, stamina, and patience are necessary to achieve weight reduction. Many diets have been devised for weight reduction. They are mostly effective because of the restriction of calorie intake that they prescribe. A diet of less than 1000 calories per day (approximately 50% of an average daily food intake in Sweden) will cause weight loss in most people and if correctly constructed need not be deleterious to health, even if maintained for months. Support from a dietician is helpful. Contrary to widespread belief, physical exercise alone is not very effective in weight reduction, although it is perceived as more entertaining than is dieting. Several oral medications are available for reduction of appetite and reduction of calorie uptake, but over time they will generally contribute to reduction of few kg body weight (< 6-8 kg over 6-12 months). Several medications used in the treatment of type two diabetes will also cause moderate weight reduction in obesity by lowering the release of insulin. Achieving and maintaining weight reduction may even eliminate early type 2 diabetes and the need for stimulating increased release of insulin. Surgical procedures to reduce or bypass the intestinal absorption of calories in food are very effective in achieving weight reduction, but they often cause severe physical and psychological side effects and are reserved for patients with serious degrees of obesity. Liposuction is not recommended for bodyweight reduction.