Does food restriction increase life span in lean rats?

The effect of food restriction on survival of lean animals was investigated using WAG/Rij rats. In this strain, body weight of males and females fed ad libitum reached a plateau of 350 g and 220 g, respectively, at the age of 10 months. Their spontaneous food intake was 15 g per 24 h in males and 10 g in females, values which were 50 to 40 % lower than that reported for most strain of laboratory rats. A 30 % food restriction was initiated at the age of 10 months in both gender, and also at 20 months in males. In females, reduction in caloric intake had no effect on mean survival until 30 months, but change the slope of the survival curve in the last part of life. As a result, mean and maximal life span were increased by 10 %. In males, when reduction in food intake was initiated at 10 months, the survival curve of the restricted animals was shift to the right, also corresponding to a 10 % increase in mean and maximal survival, without change in the slope of mortality curve. When started at 20 months, diet restriction has no significant effect on survival of male rats. It was concluded that food restriction initiated in adults is mostly efficient to increase survival in rodents with large spontaneous food intake, but have a minor effect on lean strain, although it has beneficial effect on several aging processes.