As noted in a recent research paper:
Caloric restriction (CR) causes a reduction in body temperature which is suggested to contribute to changes that increase lifespan. Moreover, low [body temperature] has been shown to improve health and longevity independent of CR. ... Based on current evidence, it is concluded that low [body temperature] plays an integral role in mediating the effects of CR on health and longevity, and that low [body temperature] may exert independent biological changes that increase lifespan. Our understanding of the overlap between CR- and [body temperature]-mediated longevity remains incomplete and should be explored in future research.
Calorie restriction causes increased health and longevity by triggering a set of programmed changes in the complex operation of metabolism. Even though the mechanisms of calorie restriction are far from completely understood, the programmed nature of this metabolic response is demonstrated by the fact that some strategic gene deletions can prevent calorie restricted laboratory animals from gaining health and longevity benefits.
There is reason to believe that enhanced longevity resulting from low body temperature is similarly a programmed response, for all that even less is known about the details of what is taking place under the hood. The hypothalamus is involved in both cases:
Temperature is an important modulator of longevity and aging in both poikilotherms and homeotherm animals. In homeotherms, temperature homeostasis is regulated primarily in the preoptic area (POA) of the hypothalamus. This region receives and integrates peripheral, central and environmental signals and maintains a nearly constant core body temperature (T(core)) by regulating the autonomic and hormonal control of heat production and heat dissipation.
Temperature sensitive neurons found in the POA are considered key elements of the neuronal circuitry modulating these effects. Nutrient homeostasis is also a hypothalamically regulated modulator of aging as well as one of the signals that can influence T(core) in homeotherms.
Nothing in biology is simple, and the effects of temperature and calorie restriction involve overlapping feedback loops and shared mechanisms in our cells. These further overlap with the programmed control of other important processes, such as hormesis and autophagy. A living being is a very, very complex system - less like a line of neat, isolated switches, and more like a bucket of unlabeled dials and levers, all of which are partially wired to the others.