This book deals with regulation of obesity by oral administration of Rhinacanthus nasutus (Linn) Kurz methanolic Extract in Rat models. Obesity is a condition with increase in energy intake and a decrease in energy output. In modern society, Obesity is a severe problem due to rapid lifestyles, consumption of high dietary carbohydrates and fat with reduced energy causes negative effect on health. The present work deals with screening of methanol extract of R. nasutus leaf (RNME) on high-fat diet fed rats. The Biochemical changes in Blood Serum and Kidney and Testis were observed in high fat diet (HFD) induced obsess rats. The Lipids profiles (triglycerides, total cholesterols) and enzyme activities viz., SOD, GST, GPx and GR were decreased and CAT activity increased in HFD rats treated with RNME. The morphological and histological changes of Kidney like the glomeruli, necrotic tubular epithelial cells and dark pyknotic nuclei and in testis tissues normal seminiferous tubules, normal spermatogonia and sperm flagella indicating regenerative changes were observed in HFD+OL, HFD+RNME treatment.