The aging of the world population together with the epidemic of obesity, raises serious concern for health care systems in developed countries. The prevalence of obesity in old people has dramatically increased in recent years: in the United States represents nearly 30% in men and in women aged 60 years and over, with an increase also in extreme degrees of obesity. Spain and Italy showed similar patterns in studies carried out between 2006 and 2011. Normal aging itself is associated with a progressive increase in fat mass, which normally peaks at about age 65 years in men and later in women. Body fat distribution also changes with age, with visceral abdominal fat increase, and subcutaneous abdominal fat decrease. Moreover aging is also associated with ectopic fat deposition within nonadipose tissue such as the skeletal and cardiac muscle, liver and pancreas. Age related changes in fat deposition occur even without significant changes in body mass index (BMI) or body weight. In the meantime, age associated loss of muscle mass and strength occurs even in relatively weight stable healthy individuals.With aging, loss of muscle mass and gain in fat seem to be linked to each other and contribute, in the presence of positive energy balance, to the development of SO. Identification of elderly subjects with SO could help to identify a group of subjects with particularly high health risk, and the concept of SO may help to clarify the relation between obesity, morbidity and mortality in the elderly. Recently, great effort has been done to improve sarcopenia definition in order to get it carried out in the clinical assessment of elderly people. However, similar effort seems to be mandatory also for SO definition.