With over 385 refereed publications, he has won several national and international awards for his work in diabetes epidemiology, diabetes in pregnancy and diabetes service development. Professor Simmons was awarded the Norbert Freinkel Award 2020 from the American Diabetes Association for his work in Diabetes in pregnancy. He is a past president of the Australasian Diabetes in Pregnancy Society (ADIPS) and was a member of the World Health Organisation technical working group on the criteria for hyperglycaemia in pregnancy. He was previously the chair of Diabetes UK Health Professional Education Steering Group. He was a visiting Professor to the University of Orebro Sweden and is a Professorial Fellow at the University of Melbourne.