The increased prevalence of obesity is recognized as one of the most serious public health problems affecting millions of people. Although some anti-obesity drugs are currently licensed for use, these drugs involve diverse side effects such as diarrhea, vomiting, and low efficiency. Here we developed a safe and efficient biomaterials-based anti-obesity nanosystem (PCG-EPL/miR33agonist), which was formed with poly (citric acid)-glycerol-polylysine (PCG-EPL) and miR33 agonist by self-assembly. The PCG-EPL could efficiently load, protect and deliver the miR33 agonist into the adipocytes and decreased the obesity-related IL-1β expression in adipocytes in vitro. The high-fat diet induced obese rat model experiment showed that the PCG-EPL/miR33agonist via caudal vein injection effectively reduced the body weight by enhancing lipid metabolism and decreasing the inflammatory factors expressions (IL-1β, TNF-α and IL-6) in vivo, without suppressing the appetite of rat. Compared with the obese mice, mice in PCG-EPL/miR33 had higher average food intake but lower energy conversion rate. PCG-EPL/miR33agonist significantly inhibited the growth of adipocytes. Noteworthy, this weight loss strategy is not only safe and efficient, but also does not need diet control. Thus, PCG-EPL may serve as an ideal platform for RNA drug delivery in anti-obesity therapy, especially for those who need to lose weight but unable to autonomously control their diet.