Malnutrition is a frequent condition, both widely represented in geriatric population and underestimated in diagnostic and therapeutic work-up, and is known to affect health status and life expectancy of elderly people. The unexpected weight loss is a pathological condition, recently classified in three different ways (sarcopenia, wasting and cachexia) according to criteria of nutritional intake, functional abilities and age-related body composition modifications, that is caused by social psychological and medical factors. In this review, the authors highlight the ways that, through malnutrition, could lead to an impairment of quality of life in elderly people. Notwithstanding the great impreciseness and confusion that surrounds the term 'quality of life', the authors focus their attention on the correlation existing with the recently occurring changes to patients' health status and life-style, analysing the relationship with frailty, failure to thrive and homeostatic balance failure syndrome. With the latter term, the authors introduce a pathological condition widely represented in the late stages of malnutrition that often evolves in multiple organ failure and lastly in the death.