Dr Clifton is the Director of CSIRO's Nutrition Clinic, which was established in the mid 1980s to carry out human volunteer trials in a range of food and diet-related areas. The Total Wellbeing Diet Book, which Dr Clifton co-authored with CSIRO colleague Dr Manny Noakes, is the result of many years research into and trials of the effectiveness of high protein diets for weight loss.

Dr Clifton leads CSIRO Human Nutrition's primary research focus in Adelaide, South Australia - dietary and lifestyle strategies for the control of obesity and obesity-related conditions. His research interests are fuelled by first-hand evidence and experience as a practising endocrinologist at the Royal Adelaide Hospital and the Flinders Medical Centre, in Adelaide. He has qualifications as a specialist physician from Australia and the UK and is an Associate Professor of Medicine at The University of Adelaide.

Dr Clifton has been awarded an MBBS, a Bachelor of Medical Science and a Doctor of Philosophy and is a Fellow of the Royal Australiasian College of Physicians (FRACP) and a Member of the Royal College of Physicians (MRCP).