Diet and physical activity are two major lifestyle factors that play a role in the prevention or management of debilitating conditions affecting older people. Both under- and overnutrition predispose to diseases. Low sodium and high potassium intakes, as well as the consumption of fruits and vegetables are associated with a reduction of hypertension and diseases arising from hypertension such as stroke and dementia. Dietary patterns (consumption of quantity and types of fats, cholesterol, vegetable oils, fish) are important in the prevention of coronary heart disease. Calcium and vitamin D intakes are important factors in the development of osteoporosis, while various dietary factors have been linked to the development of cancer. Physical activity is important in the prevention of functional decline and increased survival, reduced incidence of falls and fractures, and has various cardiovascular health benefits. Apart from prevention of diseases, exercise also has an important role in improving function in some chronic diseases such as heart failure or chronic obstructive pulmonary disease. Both diet and exercise interact, so that public health recommendations often take the form of lifestyle modification advice in the prevention of disease and disability.