Demographic data appear to demonstrate an increase in the number and ratio of elderly world-wide. Authors give a short survey on physiological alterations occurring at older age, on methods suitable for assessing nutritional status and criticism thereof. Nutritional and life style habits are also discussed. Prevalence of obesity and undernutrition and their sequelae are likewise presented. Diagnosis of undernutrition by using questionnaire can significantly improve the efficiency of family doctors' activity. Authors provide recommendations for improving nutrition and life style in healthy persons with optimal body mass, and for obese and undernourished subjects.