Obesity is a serious condition which is characterized with weight gain or with an increased amount of the fat tissue. It occurs when energy intake exceeds energy expenditure over the long-term. As a result, the fat tissue accumulates and weight goes up. However, excessive energy intake is not the only factor contributing to the development of obesity. The main cause of obesity is the combination of life style (approx. 50 %) and genetic predisposition. Obesity and type 2 diabetes are becoming lifelong diseases not only in developed countries; some scientists even speak about obesity pandemics. It is mainly Western Europe and North America where a number of obese children is on the increase. All over the world there are over 1 billion overweight people, of whom 300 million are obese.
Obesity is usually determined by reference to a Body Mass Index. BMI values greater than 25 are overweight. An individual is considered obese if his BMI exceeds 30. However, if BMI is accompanied with other risk factors, such as type 2 diabetes, obesity is diagnosed already at a BMI of 28.