Emerging evidence indicates that astrocytes modulate energy metabolism and homeostasis. However, one important but poorly understood element is the necessity of astrocytes in the control of body weight. Here, we apply viral vector-assisted brain-region selective loss of astrocytes to define physiological roles played by astrocytes in the arcuate nucleus of the hypothalamus (ARH) and to elucidate the involved mechanism. We find that astrocyte loss potently augments body weight in adult mice fed chow or high-fat diet. Mechanistically, we find that the loss of astrocytes reduces adipose tissue norepinephrine (NE) contents and chemogenetic stimulation of adipose tissue sympathetic inputs reverses the astrocyte loss-induced increase in body weight. Collectively, our findings in this study suggest a crucial physiological role of astrocytes in preventing diet-induced energy surfeit and obesity by modulating adipose tissue lipid metabolism through central sympathetic outflows to adipose tissues.