Abnormalities of energy balance present major public health problems with rapidly increasing prevalence. They include changes of body weight (BW) and/or body composition. Obesity is defined as excessive accumulation of body fat, while wasting disorders are characterized by progressive loss of BW, especially that of muscle mass. During aging two common tendencies are observed: middle-aged people tend to gain weight and develop obesity, while at old age, anorexia (loss of appetite) with a consequent cachexia and progressive muscle atrophy (sarcopenia) develops. As population aging became a global phenomenon, the impact of middle-age obesity and aging anorexia is enormous. Moreover, obesity appears to accelerate aging and age-related degenerative processes (e.g. muscle atrophy, neurodegeneration).
Age-related changes can be observed not only in humans, but also in other mammals suggesting the contribution of altered basic regulatory mechanisms, in addition to environmental factors (e.g. increasingly sedentary lifestyle and imbalanced dietary choices). One of the common features of aging and obesity is a dysregulation of energy homeostasis. Such dysregulation involves resistance to different regulatory peptide hormones, e.g. leptin or insulin, leading to abnormalities of BW and/or body composition.
As both types of body composition changes increase the risk of morbidity and mortality, investigation of regulatory alterations that develop in obesity or during the course of aging is of outstanding importance
