Researchers here make the point that calorie restriction studies in animals are also introducing a strong component of time restricted feeding, as animals tend to be fed once a day.
Studies of intermittent fasting without calorie reduction have shown that this can produce a similar set of metabolic responses to a reduced calorie intake. Intermittent fasting and calorie restriction have been shown to improve health and extend healthy life spans via two overlapping sets of mechanisms, as assessed by various omics approaches.
Thus the details of the approach to feeding animals any given fixed amount of calories (delivery of food per a day versus the same caloric intake split between several deliveries spaced over the day) will likely bias the results of any study.
Source: Fight Aging!