Obesity, associated with a series of complications such as diabetes, hypertension, and heart disease, is a great threat to human health and leads to increased morbidity and mortality. Despite the presence of anti-obesity agents on the market, the application of these drugs is limited because of their typical side effects. More effective and safe weight-loss drugs are being pursued by many researchers, correspondingly, growing small molecules and natural products with anti-obesity effects have been identified and the molecular mechanisms underlying the action of the novel and known compounds have at least partially been revealed. Therefore, the field does witness great progress year by year. In this review, we intend to provide a comprehensive and updated view on the known and novel compounds which possess anti-obesity effects and further classify them according to the molecular mechanisms of their actions in regulating the major anti-obesity pathways.