Objectives: Obesity, which is a risk factor for diabetes, hypertension, cardiovascular diseases, and cancer, is caused serious health problems and economic costs on a global scale. Nowadays, pancreatic lipase inhibitors that cause inhibition of lipid digestion and lipid absorption are one of the limited treatment approaches for obesity. Plant-derived secondary metabolites can be used for treating obesity. The aim of this study was to research the antiobesity potential of Amaranthus albus L. (Amaranthaceae), Helichrysum compactum Boiss. (Asteraceae), Chenopodium album L. (Chenopodiaceae), and Agrimonia eupatoria L. (Rosaceae). Materials and Methods: To detect the antiobesity potentials of the plants, in vitro lipase inhibitory activity studies by spectroscopic method and quantitative analysis studies of some anti-obesity effective secondary metabolites by reversed-phase high performance liquid chromatography (RP-HPLC) technique were carried out. Results: In vitro lipase inhibitory studies showed that all plant extracts possess lipase inhibitory effect, and the highest lipase inhibitory potential was observed for H. compactum (IC50: 45.70 μg/mL ± 2.3618). According to HPLC analyses, p-coumaric acid (0.27 mg/g) in A. albus; benzoic acid (0.33 mg/g) in C. album; vanillic acid (7.32 mg/g), syringaldehyde (14.97 mg/g), quercetin (4.66 mg/g), p-coumaric acid (0.71 mg/g), and benzoic acid (3.43 mg/g) in H. compactum; p-coumaric acid (0.71 mg/g) and benzoic acid (3.43 mg/g) in A. eupatoria were detected. Conclusion: In conclusion, H. compactum is the most remarkable natural source for the study. The fact remains that all plants may be promising candidates for treating obesity.