Leo studied medicine at the University of Frankfurt going on to work as an assistant doctor at the Center for Anesthesia and Resuscitation at the Frankfurt University Hospital. Receiving recognition as a specialist in anesthesia and resuscitation, and after two years at the BG Trauma center, was a scholarship holder at the University hospital Frankfurt, Center for Anesthesia and Resuscitation. After 12 years working at the Institute for Anaesthesiology and Pain Therapy at the Northwest Hospital as senior advisor, he went on to become the medical advisor for emergency medicine for the health protection authority of the city of Frankfurt am Main. In 2006 he became medical director of the emergency medical service (ÄLRD) for the city of Frankfurt.
These days, Leo is a member of the board of directors of the Central Council of Jews in Germany, a board member of the Jewish Community in Frankfurt, deputy chairman of the board of the Central Welfare Office of Jews in Germany (ZWST), and a member of the Hessian Integration Advisory Board and the German Ethics Council.
He works through the Resilience Advisors Network on projects designed to improve European emergency medical resilience.