Distinguished Professor Simmons, is Chief Medical Officer for Diabetes Australia, Professor of Medicine at Western Sydney University, District Advisor on Diabetes for the South Western Sydney Local Health District and previous Director of the Macarthur Diabetes Endocrinology and Metabolism Service in Sydney, Australia. Before returning to Australia in 2014, Professor Simmons was the Clinical lead for the Diabetes service at Addenbrookes Hospital, Cambridge UK. With over 500 refereed publications, he has won several national and international awards for his work in diabetes epidemiology, diabetes in pregnancy and diabetes service development including the American Diabetes Association 2020 Norbert Freinkel Award and 2022 Diabetes in Pregnancy Study Group Pederson Awardee.  He is the immediate past president of the Australasian Diabetes in Pregnancy Society (ADIPS). He was the trial coordinator for the DALI lifestyle RCT to prevent GDM and is the Chief Investigator for the TOBOGM study the first large RCT of diagnosing and treating early gestational diabetes mellitus. He remains a practising endocrinologist holding weekly diabetes in pregnancy clinics.