Department of Human Biology, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands. Address for correspondence: Klaas R. Westerterp, Department of Human Biology, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands. tel. 31 43 3881628. fax 31 43 3670976. email K.Westerterp@HB.Unimaas.NL

Abstract: Increasing age is associated with changes in physical activity and loss of fat-free mass. The question is whether an active life style can delay the progressive loss of fat-free mass and functional capacity. A review of available evidence from doubly labeled water studies showed that there is no association between fat-free mass and the level of physical activity in subjects over 60. Physical activity does not seem to affect the age-induced loss of fat-free mass. However, an active life style has positive effects on muscle function and thus is an important determinant of independent living at old age.

Key words: aging, doubly labeled water, exercise training, nutrition, fat-free mass, muscle mass, elderly