Burdock (Arctium lappa L) root is eaten as a vegetable in many countries and used as an ethnomedicine because of its various pharmacological effects. The objective of this study was to investigate the underlying mechanisms of ethanolic extract of root from Arctium lappa L root (ALE) to lose weight and regulate lipid metabolism. The results showed that ALE can regulate lipid metabolism level and inhibit the weight gain of rats induced by the high‐sugar and high‐fat diet. The contents of triglyceride and cholesterol in the liver of obese rats significantly reduced, and hepatic steatosis was ameliorated. In addition, this study identified that ALE enhanced hepatic fatty acid β‐oxidation and ameliorated hepatic steatosis by activating AMPK/ACC/CPT‐1 pathway. These results indicated that ALE has a potential preventive and therapeutic effect on metabolic‐associated fatty liver disease and obesity. Practical Applications Obesity is already a global health problem. Obesity causes accumulation of triglycerides, which leads to hepatic steatosis. Long‐term steatosis causes liver damage and metabolic fatty liver disease. Plant‐derived functional foods or herbal medicines have better effects on weight loss and liver protection, which are more conducive to long‐term use with less toxic side effects. As a medicinal and edible plant material, Arctium lappa L root has the effect in losing weight. Our study showed that ethanolic extract of Arctium lappa L root effectively regulates lipid metabolism and inhibits hepatic steatosis. Arctium lappa L root may be used as a therapeutic drug and functional food raw material for obesity and fatty liver disease.