Our Medical Staff

We are dedicated to helping you achieve your weight-loss goals.

Dr Brendan Ryan


Dr Ryan is a bariatric surgeon with over 15 years of experience in the field of obesity surgery. He has performed over 5000 weight loss operations. He specialises in Gastric Sleeve, Gastric Bypass and Revisional Bariatric surgery. He also has an interest in Anti-reflux, Hiatal Hernia and Gallbladder surgery.

Dr Ryan has rooms in Westmead and Campbelltown and operates privately at Westmead Private, Lakeview Private and Campbelltown Private Hospitals.

He has public appointments at Westmead and Blacktown Hospitals.

Dr Ryan has been awarded Surgeon of Excellence in Bariatric and Metabolic Surgery. Sydney Bariatric Clinic has proudly been recognized as a International Centre of Excellence in Bariatric Surgery also.

Dr Ryan contributes to the National Bariatric Registry and is part of the Research team of Sydney Bariatric Clinic which presents regularly at National and International Bariatric Meetings. He is committed to maintaining best practices in weight loss surgery.

Dr Nicholas Cocco


Dr Nicholas Cocco is a General and Bariatric Surgeon, having trained in NSW, ACT and Victoria. He offers in-person consults and telehealth consultations where appropriate.

He completed his fellowship in 2018 and post fellowship training in kidney and pancreas transplantation surgery. During this time, he completed additional work in elective and acute general, laparoscopic and vascular surgery.

‌Dr Cocco joined Sydney Bariatric Clinic in 2020 and provides a range of general and bariatric / metabolic surgical procedures including:

  • Bariatric / metabolic surgery – gastric sleeve, bypass surgery, removal of gastric bands and Minimizer rings, and revision of previous surgery to another weight loss procedure
  • Upper endoscopy and reflux management/surgery
  • Hernia surgery – both open and laparoscopic / keyhole surgery
  • Gallbladder surgery
  • Medical management of obesity and post-bariatric surgery management

Dr John Leyden


Dr John Leyden is Sydney Bariatric Clinic’s lead anaesthetist with over 15 years of experience in providing comprehensive and tailored perioperative and anaesthetic care for all patients undergoing metabolic/bariatric surgery. Additionally, Dr Leyden has 20 years of experience in cardiothoracic anaesthesia. His expertise means Sydney Bariatric Clinic can safely care for even the most medically complex patients.

Dr Leyden completed a clinical fellowship in Cardiac Anaesthesia at the University of Toronto, Canada, St Michael’s Hospital campus. He is the founder and chairman of NeuroEndocrine Cancer Australia (formerly known as the Unicorn Foundation), a not-for-profit charity for patients with rare neuroendocrine cancers.

Dr Leyden is passionate about providing tailored anaesthesia care for each of his patients. He creates recovery programs that ensure all patients receive the highest level of care at SBC’s pre-operative clinic.

Dr Tony Brancatisano


Dr Tony Brancatisano is a senior bariatric medical practitioner, research scientist and surgical assistant in bariatric surgery. He has over 15 years of experience in weight loss management. This includes the pre-operative assessment, post-operative and long term management of patients with obesity undergoing gastric banding, sleeve gastrectomy, gastric bypass operations and revisional bariatric procedures. He is a medical graduate of the University of Sydney.

Dr Tony is part of the allied health team involving dietitians, psychologists and exercise consultants. The allied health team provides guidance and support throughout every patient’s weight loss journey. Dr Tony is dedicated to achieving the best outcome for every patient through his personalised and comprehensive approach. He understands that obesity is a complex chronic disease and that bariatric surgery requires lifelong follow up and care; a partnership between the patient, the clinic, and the patient’s regular GP.

Dr Tony consults regularly at Westmead Private and Campbelltown.

Catherine Underwood


Catherine is an accredited practising dietitian and nutritionist with extensive experience supporting patients with their weight loss and health goals post-bariatric surgery. Catherine supports you to pass smoothly through the stages of dietary progression after weight loss surgery. She also serves as a valuable support to ensure sustained weight loss in the long term, no matter what hurdles life throws in your direction. Catherine will work with you to implement healthy eating behaviours that fit your lifestyle. This work will also focus on the psychology behind the food you eat.

Catherine is extremely knowledgeable and passionate about diet and nutrition. She finds working with patients extremely rewarding and loves being part of the process that sees patients achieving life-changing results.

Catherine is based at SBC’s Westmead clinic.

Tania Chaanine


Tania is an accredited practicing dietitian and accredited nutritionist specialising in the management of obesity. She completed her Bachelor of Science and Honours in Nutrition and Dietetics at the University of Sydney. Additionally, Tania is a member of the Dietitians Association of Australia and a FODMAP certified dietitian.

Tania has been working in the area of weight loss surgery for over 10 years alongside leading bariatric surgeons in Sydney. She is dedicated to delivering the highest level of care by providing an individualised evidence-based approach. Tania looks forward to working with you to help you achieve the best outcome possible.

Tania is based at SBC’s Westmead and Campbelltown clinics.

Dr Cal Paterson


With over a decade of experience in bariatric psychology, Cal has worked with patients of all ages across a diversity of backgrounds, in both surgical and non-surgical care teams. Cal works with patients at an individual level to untie the knots of confusion and guilt around self-care. Cal believes a tailored approach is important. Cal works around the notion that every body, every person’s life is unique to them, and so each person needs to find their own unique pathway to health.

Cal is based at SBC’s Westmead clinic.

Dr Caitlin Antoon


Caitlin is a clinical psychologist. She has clinical experience in both public and private mental health sectors, working with patients who present with a diverse range of challenges and levels of risk.

As a clinician with experience in the bariatric medical context, Caitlin offers a therapy experience that is tailored and unique to the surgery process. She also treats mental health difficulties that are likely to affect surgery outcomes, or that prevent a patient from living life to the fullest.

Claire Ryan


Claire is our practice manager and nurse who supports all the patients through their weight-loss journey. She works closely with Dr Ryan and rest of the team to answer any medical or nursing queries or concerns you might have at any stage of the program.

You will meet Claire at the pre-operative clinic if you decide to go ahead with surgery and she will provide information about all aspects of the process, the surgery, the recovery and after care. She will also see you regularly after surgery both in the hospital and later in the rooms.

Her goal is to ensure all patients receive all the necessary medical attention they deserve when going through this life-changing treatment.

Amanda Cromack


Amanda is one of our Practice Nurses at Sydney Bariatric Clinic. Amanda is a senior, highly skilled nurse having worked as a Registered Nurse in Western Sydney for over 20 years. She has a lot of experience in surgical care of patients having been a Clinical Nurse Specialist, Nursing Unit Manager and Clinical Nurse Educator. Amanda is also currently still working as a Anaesthetic nurse. Amanda also is the nurse in charge of iron infusions at our clinic. Her key focus is on being approachable and supportive for patients during their whole journey.

Our Support Team