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Fellows Directory

Stephen O'Rahilly

Sir Stephen O'Rahilly FMedSci FRS


Elected: 2003


Stephen O’Rahilly is an endocrinologist who has transformed our understanding of the genetic causes of obesity. Stephen showed that mutations in single genes caused a catastrophic loss of control of appetite and feeding behaviour, leading to severe obesity. However, he also demonstrated that these inherited disorders could be treated very effectively.

Stephen studies patients with extreme and inherited metabolic conditions such as severe obesity and insulin resistance. His work first established that some very obese children have a mutation in the gene for leptin — an appetite-controlling hormone. He has since revealed the genetic basis for around 20 disorders and works with industry to develop targeted treatments.

From modest beginnings, Stephen has built up and leads one of the world’s largest institutes for metabolic research at the University of Cambridge. His findings have been recognised internationally with many awards and prizes, and in 2013 he was knighted for services to medical research.

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