Article history: Received 18 July 2014 Objective: To know the impact of Piper betel leaf stalk (P. betel) extract on Protein and energy metabolism and its role in male albino rats. Methods: Healthy adult (3-4 months old) male Wistar strain albino rats were administered with betel leaf stalk extract, at the dose of 50 mg/ kg/day through oral gavages for 15 days. Twenty four hours after the last dose, the animals were autopsied. In order to assess antifertility effect in testis, epididymis, seminal vesicle and prostate gland, estimation of total, soluble and structural proteins, free amino acids and DNA, RNA were undertaken. Results: The accumulation in proteins indicates the anti-androgenic effect of extract. The reduction in free amino acids will affect the sertoli cell function, results in the damage of spermatogenesis. The significant elevation in testicular DNA content (hyperplasia) was observed. In the present study, P. betel leaf stalk extract decreases the concentration of RNA, in testes, seminal vesicle and prostate gland except in epididymis where it was elevated. It indicates the alterations in rate of protein synthesis and growth rate of tissues due to the administration of P. betel leaf stalk extraction. However, the RNA: DNA ratio was reduced except in prostate. Conclusions: P. betel leaf stalk extract exert its anti androgenic effect by alterations in rate of protein synthesis and cellular hypertrophy occur in prostate.