Abstract: To test the hypothesis that mammals that show decrease in body mass under short-day condition should be resistant to high-fat induced obesity, we traced the changes of energy balance in a wild rodent, Brandt's voles (Lasiopodomys brandtii), which were acclimated to either long day (16L: 8D, LD) or short day (8L: 16D, SD) and fed either low-fat diet (LFD) or high-fat diet (HFD) in each photoperiodic manipulation. We found that Brandt's vole was not resistant to high-fat diet-induced obesity and SD, not HFD, induced the elevation in basal metabolic rate, the maximal rate of oxygen consumption after norepinephrine injection, and uncoupling protein 1 content in brown adipose tissue. HFD caused the increase in apparent digestibility and body fat mass, and the decrease in energy intake in both LD and SD voles. The enhancement of energy absorption associated with small intestine tissue recruitment can compensate the lower energy intake, which may contribute to the high-fat diet-induced body fat deposition. Thus, a decrease in body-weight gain but has no resistance to high-fat induced obesity implies an evolutionary and adaptive mechanism which is a benefit for their winter survival.