In female mice on a control diet (3.6% fat) reduced physical activity leads
to a reduction of the average life span. So the average age at death of an
inactive group is 500 +/- 166 compared to 565 +/- 175 days in an active co
ntrol group. If the animals are kept on a fat rich diet (12.4% fat) this ef
fect of physical activity restriction is no longer observable and the avera
ge age at death is 570 +/- 142 days, within the range of the control animal
s. The increased fat intake seems to reduce the stress or to increase the r
esistance to stress in the activity restricted animals. So stress is a cruc
ial determinant of life span. (C) 1998 Elsevier Science Ireland Ltd. All ri
ghts reserved.