Mr Efthimiou undertook his basic surgical training in London and pursued his research interests at the Imperial Cancer Research Fund in Hammersmith Hospital where he investigated molecular and cellular changes in pancreatic cancer. He completed his higher surgical training in The Wessex Deanery and developed a specialist interest in upper gastro-intestinal and laparoscopic surgery. He spent his final year in training at The Royal Marsden Hospital in London. Subsequently he obtained an advanced fellowship in laparoscopic bariatric surgery at McGill University Health Centre in Montreal, Canada under Professor N. Christou; President of the Canadian Association of bariatric surgeons. He returned to UK where he was appointed as a consultant in general and bariatric surgery at Chelsea and Westminster Hospital.
His expertise is in general surgery, minimally invasive (key hole) upper gastrointestinal surgery (gall stones, surgery for gastro-oesophageal reflux disease, hernia surgery) and bariatric (weight loss surgery).
He has authored many papers both in general surgery as well as bariatric surgery and presented in prestigious National and International conferences. He both lectures and organises courses for other surgeons. His interests lie in furthering research and educational development in the field of bariatric surgery.