Obesity, which was evaluated positively in our culture in past periods and which was even considered by some to be merely an aesthetic question, is a disease with serious consequences for the health of the person suffering from it, and for the economy of those who have to meet its costs. Its present prevalence in Spain is situated around 13% and, if we can trust the forecasts established for other western countries such as the USA, it will increase to become the epidemic of the present century. The consequences of excess weight on the cardiovascular, respiratory, digestive, osteoarticular, reproductive and endocrine-metabolic systems are well known, as well as the relation between obesity and some types of cancer. As a general rule, it is worth bearing in mind that the greatest complications will correspond to the greater overweight (morbid obesity and severe obesity) and that age, the duration of ponderal excess and the distribution of the additional fat also have an influence, given that android/visceral/abdominal obesity is accompanied by the so-called insulin resistance syndrome. It is thus usually accompanied by hypertension, dyslipemia, alterations of hydrocarbonate tolerance and coagulation, elements involved as a whole in cardio-vascular morbi-mortality.