Michael Mosley obituary: Medical doctor who became a TV diet guru

Mosley, who promoted intermittent fasting, said he did more good with one programme than he could have in 30 years of practice as a doctor

Dr Michael Mosley died while on the Greek island of Symi. Photograph: Jonathan Player/The New York Times

Born: March 22nd, 1957

Died: June 9th, 2024

Dr Michael Mosley, who has died aged 67 on the Greek island of Symi, explored health and fitness issues of interest to big audiences. He was a versatile communicator, whether as a television diet guru, newspaper columnist or podcaster.

He became a household name for diet books promoting calorie reduction and fasting, including The Fast Diet (2013), written with the journalist Mimi Spencer. His work gained in popularity from his self-experimentation, which included swallowing tapeworms, magic mushrooms, internal cameras and – most famously – fasting to cure his own type 2 diabetes, diagnosed in 2012. He became a well-known TV and radio celebrity medic, regularly appearing on The One Show for the BBC and This Morning for ITV. On BBC Radio 4’s Just One Thing podcast he offered health tips to the nation, from the benefits of daily spoonfuls of olive oil to the usefulness of the plank position.


Yet his own medical career was brief. Mosley, who studied philosophy, politics and economics (PPE) at New College, Oxford, trained in medicine at the Royal Free Hospital, north London, after two years of working as a banker. He wanted to become a psychiatrist, saying that he found people more interesting than finance, but was disappointed to find that “there were severe limitations to what you could do”, he told the British Medical Journal in 2004.

He opted instead to exert influence through the medium of television, joining the BBC training scheme as an assistant producer in 1985, and going on to produce documentaries based mostly in science, mathematics and history.

His most glorious moment arguably came with the Horizon programme Ulcer Wars, which he made in 1994 about the work of Barry Marshall of the University of Western Australia, who was convinced that the bacteria he had identified called Helicobacter pylori was responsible for most gastric cancers and ulcers.

The story appealed to Mosley and inspired his own self-experimentation: Marshall had drunk a solution of H pylori from a beaker in the 1980s and his stomach had been colonised by the bacteria, which disappeared when he took antibiotics.

Marshall was right and later, with his colleague Robin Warren, won a Nobel Prize. Mosley received more than 20,000 letters from people cured of their ulcer pain by antibiotics. The film brought him awards. “I probably did, in a funny way, more good with that one programme than if I had stayed in medicine for 30 years,” said Mosley in the BMJ.

In 2002 Mosley was nominated for an Emmy as executive producer on the documentary featuring John Cleese, The Human Face. In 2013 he began to host the series Trust Me, I’m a Doctor for the BBC. His most recent TV series were for Channel 4: Who Made Britain Fat? (2022) and Secrets of Your Big Shop (2024).

The Fast Diet book, which launched the 5:2 diet, also came out of a Horizon documentary. Eat, Fast and Live Longer (2012) was inspired by Mosley’s own diagnosis of type 2 diabetes, which is linked to excess weight. The disease ran in the family. His father, Bill, had died of the complications at the age of 74. Mosley came across the American neuroscientist Mark Mattson’s work on intermittent fasting, and adopted the pattern he advocated of normal eating for five days and consumption of just 500-600 calories on the other two.

He claimed to have lost 20lbs and reversed his own type 2 diabetes. Mattson appeared in the documentary, which is credited with popularising the 5:2 diet. In 2021 Mosley published The Fast 800 Keto, which combines fasting with a ketogenic diet, high in fat and low in carbohydrates, but in its later stages allows carbohydrates back in.

Mosley’s diet work was controversial because of its focus on calorie reduction to lose weight. In 2021 the eating disorder charity Beat said of his Channel 4 series Lose a Stone in 21 Days that “the programme caused enough stress and anxiety to our beneficiaries that we extended our helpline hours”.

He said he had suffered from chronic insomnia from his late 30s. That became the subject of another BBC documentary and also a book published in 2019, called Fast Asleep.

Born in Calcutta (Kolkata), India, Michael was the son of a banker, Bill Mosley, and his wife, Joan. At the age of seven he was sent to boarding school in Britain. Mosley said in an interview with the Sydney Morning Herald that his mother was heartbroken to send him away to school, but that his father worked in Hong Kong and the Philippines, and wanted Michael and his other son, John, to become bankers as he had, and sending children to boarding school back in Britain was part of the culture of that time.

Mosley met Clare Bailey at the Royal Free Hospital medical school, now part of UCL medical school, and they married in 1987. Bailey, who became a GP, was an active partner in Mosley’s dietary work and wrote recipe books for people embarking on the Fast 800 diet as well as newspaper columns in her own right. She told interviewers that she did not fast, because she had never needed to lose weight, and that she would hide chocolate from Mosley, who had a sweet tooth. She survives him, along with their three sons, Alex, Jack and Daniel, and a daughter, Kate.