Previously we investigated the role of NPY and leptin sensitive networks in the mediobasal hypothalamus (MBH) in sleep and feeding and found profound homeostatic and circadian deficits with an intact suprachiasmatic nucleus (SCN). We propose that the arcuate nuclei (Arc) are required for the integration of homeostatic circadian systems including temperature and activity. We tested this hypothesis using saporin toxin conjugated to leptin (Lep-SAP) injected into Arc in rats. Lep-SAP rats became obese and hyperphagic and progressed through a dynamic phase to a static phase of growth.. Circadian rhythms were examined over 49 days during the static phase. Rats were maintained on a 12:12 light:dark (LD) schedule for 13 days and thereafter maintained in continuous dark (DD). After the first thirteen days of DD, food was restricted to four hours per day for ten days. We found that the activity of Lep-SAP rats was arrhythmic in DD, but that food anticipatory activity was nevertheless entrainable to the restricted feeding schedule and the entrained rhythm persisted during the subsequent 3-day fast in DD. Thus, for activity, the light-entrainable oscillator, but not the food entrainable oscillator, was disabled by the Arc lesion. In contrast, temperature remained rhythmic in DD in the Lep-SAP rats and did not entrain to restricted feeding. We conclude that the leptin-sensitive network that includes the Arc is required for entrainment of activity by photic cues and entrainment of temperature by food, but is not required for entrainment of activity by food or temperature by photic cues.