Excess body weight is a very serious problem, especially in North America and Europe. It has been referred to as a "pandemic" since it has progressively increased over the past several decades. Moreover, excess body weight significantly increases the risk of numerous diseases and clinical disorders, including all-cause mortality, coronary and cerebrovascular diseases, various cancers, type 2 diabetes mellitus, hypertension, liver disease and asthma, as well as psychopathology, among others. Unfortunately, overweight and obesity are now common in both young children and adolescents. Although the causes of excess body weight are multi-factorial, the most important factors are excess caloric intake coupled with limited energy expenditure. Therefore, lifestyle modification can significantly reduce the risk of morbidity and mortality and thereby increase longevity and improve the quality of life.