Introduction: Osteoporosis is the most represented metabolic bone disease and is characterized by the reduction of bone mineral density (BMD), exposing patients to high fracture risk and disability. Bisphosphonates (BPs) are the main compounds exploited in treatment of osteoporosis and significantly reduce fracture risk. Sarcopenia is the pathological reduction of muscle masses and strength, and many studies highlighted its co-existence in patients with impaired bone mass. Indeed, the pathological reduction of lean tissue has been linked to a higher risk of falls and, consequently, fractures and disability. Moreover, the pathological reduction of lean tissue seems to share many pathological mechanisms with impaired bone strength and structure; thus, in this context, we decided to conduct a retrospective case-control study aimed at evaluating the effects of BPs on lean mass and body composition. Material and methods: We enrolled postmenopausal women from our metabolic bone diseases outpatient clinic who underwent at least two consecutive dual-energy X-ray absorptiometry (DXA) examinations concomitantly to the beginning of an antiresorptive agent. The body composition of patients and controls was compared by fat masses, lean masses and android-to-gynoid ratio (A/G ratio). Results: A total of 64 female subjects were considered for the study: 41 starting a BPs and 23 without treatment were used as control. The fat masses and lean masses appeared to be unaffected by BPs. Conversely, A/G ratio was lower in BPs group after 18 months of therapy compared to baseline (p < 0.05). From the stratification based on the single BP we failed to highlight any significant difference between the tested variables. Conclusions: Bisphosphonates treatment did not modify lean tissues, however a significant reduction of A/G ratio in BP group was documented. Thus the BPs seems to act on patients body composition and extra-skeletal tissues but larger prospective studies are needed to evaluate whether these modifications have clinical relevance.