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 6 hours since they last saw him.
"His name is Dr Mike Mosley and he is a familiar face for many British people."
