Dr Michael Mosley is believed to have gone missing on a Greek island.
The 67-year-old is known for his appearances on television programmes including This Morning and The One Show.
He is also credited for the increasing popularity of the 5:2 diet for losing weight, which involves fasting for two days per week.
Representatives for Dr Mosley confirmed a search was ongoing for him, telling the Mirror that they were “very worried about him.”
A post on a local Facebook group in Greece said rescue teams from Athens were heading for the island.
The appeal read: "A search and rescue team is coming from Athens with drones and other more sophisticated equipment to extend the search.
"They are expected to arrive by about 1 p.m."
The post continued: "Have you seen this man? He set off to walk back from St Nick's at about 13.30 and failed to make it home. His friends are concerned as it is six hours since they last saw him.
"His name is Dr Mike Mosley and he is a familiar face for many British people."
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