Clinical Advisory
Dr. Zachary M. Callahan, MD
Bariendo Nashville Director
Board-certified bariatric and minimally invasive surgeon advancing incision-free and robotic weight-loss care
Dr. Zachary Callahan brings specialized expertise in both traditional and incisionless weight-loss surgery to Bariendo Nashville. As a fellowship-trained surgeon in primary and revisional bariatric procedures, he offers a full spectrum of advanced treatment options—including robotic sleeve gastrectomy, gastric bypass, duodenal switch, and cutting-edge incisionless approaches such as Endoscopic Sleeve Gastroplasty (ESG Stomach Tightening®), intragastric balloon therapy, and endoscopic revision of gastric bypass. His comprehensive skill set also includes incisionless treatment of Achalasia, Gastroparesis, Zenker’s Diverticulum, and early-stage cancers of the esophagus or stomach, as well as minimally invasive repair of both simple and complex abdominal wall hernias.
Dr. Callahan is committed to delivering safe, effective, and personalized care that empowers patients to achieve lasting metabolic health without unnecessary incisions or prolonged recovery times. His patient-first approach combines technical excellence with ongoing lifestyle support to maximize results and improve quality of life.
A graduate of the University of Cincinnati College of Medicine, Dr. Callahan was inducted into the Alpha Omega Alpha Honor Medical Society. He completed his surgical residency at Thomas Jefferson University in Philadelphia, where he performed over 1,100 general surgery cases, earned seven teaching awards, and served as Administrative Chief Resident. He then pursued a highly competitive fellowship in Minimally Invasive Surgery at NorthShore University HealthSystem in Chicago, training under foregut surgery expert Michael Ujiki in a program accredited in Advanced GI MIS, Bariatric Surgery, Comprehensive Flexible Endoscopy, and Foregut Surgery.
Dr. Callahan has authored more than 30 publications with over 200 citations, presenting his research at numerous national conferences. He is an active member of the Society of American Gastrointestinal and Endoscopic Surgeons (SAGES), the American Foregut Society, and the American Society for Metabolic and Bariatric Surgery.
When he’s not transforming lives in the operating room, Dr. Callahan enjoys staying active, traveling, and spending time with his wife and their Bernedoodle, “Carson”.