Background Adiposity is a major health-risk factor, and D-allulose has beneficial effects on adiposity-related metabolic disturbances. However, the modes of action underlying anti-hyperglycemic and hypolipidemic activity are partly understood. Objective This study investigated the in vivo and in vitro effects of D-allulose involved in adipogenesis and activation of the AMPK/SIRT1/PGC-1α pathway in high-fat diet (HFD)-fed rats. Design In this study, 8-week-old male SD (Sprague Dawley) rats were divided into five groups ( n = 8/group), (1) Control (chow diet, 3.5%); (2) 60% HFD; (3) 60% HFD supplemented with allulose powder (AP) at 0.4 g/kg; (4) 60% HFD supplemented with allulose liquid (AL) at 0.4 g/kg; (5) 60% HFD supplemented with glucose (AL) at 0.4 g/kg. All the group received the product through oral gavage for 6 weeks. Control and HFD groups were gavaged with double-distilled water. Results Rats receiving AP and AL showed reduced body weight gain and fat accumulation in HFD-fed rats. Also, supplementation of AL/AP regulated the cytokine secretion and recovered biochemical parameters to alleviate metabolic dysfunction and hepatic injury. Additionally, AL/AP administration improved adipocyte differentiation via regulation of the PPARγ and C/EBPα signaling pathway and adipogenesis-related genes owing to the combined effect of the AMPK/SIRT1 pathway. Furthermore, AL/AP treatment mediated PGC-1α expression triggering mitochondrial genesis via activating the AMPK phosphorylation and SIRT1 deacetylation activity in adipose tissue. Conclusion The anti-adiposity activity of D-allulose is observed on a marked alleviation in adipogenesis and AMPK/SIRT1/PGC-1α deacetylation in the adipose tissue of HFD-fed rat.