Obesity, pathological increase of body fat, has an incidence about 10-15% between adolescents in developed countries. Measurement of skinfolds determines the amount of subcutaneous fat in humans, establishing difference between normal and obese people in both sexes. It is admitted that most of the human obesity have a polygenic origin and that nutritional habits of adolescents in the last few years are able to increase obesity. This nutritional problem usually is associated with a great number of metabolic, bone and psychological disorders. Treatment is essentially based in a caloric restriction diet and in an increase of physical exercise. However, it is preferable to prevent the state of obesity because its treatment usually has a bad response.