Dietary restriction (DR)-related delay of ageing is hypothesized to be mediated by the reduction of the metabolic rate (MR). However, studies on the effect of DR on MR have produced equivocal results. We demonstrated that this lack of congruency can be due to a variation in the initial level of MR within a given pool of experimental subjects. We subjected laboratory mice from two line-types divergently selected for basal MR (BMR) to 30% DR lasting 6 months, to test whether the effect of DR depends on the initial variation in BMR and peak MR. BMR and peak MR were independently affected by DR. The effect of DR was stronger in line-types with higher initial levels of MR. Line-type specific changes in the proportions of body components explained contrasting effects of DR on the mass-corrected BMR, which decreased in the high, and did not change in the low BMR line-type. We conclude that the initial variation in MR can significantly affect response to DR. However, we found no association between the level of MR and mechanisms underlying susceptibility to or protection against oxidative stress.