Overweight and obesity are defined by the WHO as “abnormal or excessive fat accumulation that may impair health”. An adult person is overweight when their BMI is between 25 and 30, and obese if their BMI is 30 or above. BMI above 40 is considered morbidly obese. The definition for children is different as it must take age into consideration.
Obesity is a huge health problem. In 2016 were more than 39% of adults worldwide overweight and 13% of those were obese. The worldwide prevalence of obesity has nearly tripled from 1975 to 2016, which indicates that some recent change is the cause of the problem. WHO names an increased intake of energy-dense foods and an increase in physical inactivity as potential causes. Urbanized environments have higher prevalence of obesity than rural environments.
Obesity can be classified in two different ways. According to the appearance there is an “apple-type”, where fat mostly accumulates around the abdomen and viscera, and a “pear-type”, where fat mostly accumulates on the ass, thighs and hips. The former type is mostly characteristic for men and has a worse prognosis than the other type, which is mostly characteristic for women.
It can also be classified according to the size and number of adipocytes. Hypertrophic obesity is characterised by hypertrophic adipocytes and is most common in males who become obese in their adulthood. Hypercellular (or hyperplastic) obesity is characterised by increased number of adipocytes. This type is more typical in persons who develop obesity in childhood or adolescence.
30. Central and peripheral factors in the regulation of food intake and body weight. Disorders
32. Etiology and pathogenesis of obesity