NOW Gillian McKeith has flown the prime time TV nest, it seems Jimmy Doherty has taken over her unusual mantle. “When was your last (bowel) movement?” the chirpy farmer and TV presenter inquires mid-conversation.

There may be a bit of nervous laughter and faltering on my part, but not on Doherty’s when the question’s splutteringly returned.

“Well, I’m not bad as it goes,” confides Doherty, with an enviable ease of tone. “For rural Africans and Ethiopians, it’s around every 15 hours, where for the average Brit, it’s around two and a half days.”

In his new Channel 4 documentary, The World’s Best Diet, he and co-presenter Kate Quilton head to the likes of Ethiopia, France, Mexico and around the UK, to find out how our diets impact our health. With the help of experts, the one-off programme ranks 50 of the world’s diets from the very worst to the very best, in a bid to understand what we in Britain should be eating and how we can improve our health and quality of life.

As a farmer, restaurant owner, foodie and best friend of Jamie Oliver (with whom he’s co-presented various TV series), Doherty is ideally placed to tackle this weighty subject.

“We should spend more money on food. It’s a necessity and there’s a weird dichotomy in this country, where the very poor tend to have the very worst food, and then if you look at Ethiopia, in the rural areas where they’re desperately poor, they have some of the best diets.

“It’s wholesome food, but food is key and central to everything in Ethiopia, whereas in our culture it’s seen as an annoyance and we want it quick and easy, cheap and cheerful, and yet we’ll have extra money to spend on our Sky subscriptions or our latest phones.”

Doherty is ardent that we start giving food more prominence for all our sakes. “There are lots of things we can do without. We can do without emails and phones but you can’t do without food, and the poor quality food you put inside you will have an effect.”

Like many parents (he has two daughters, Molly, three, and one-year-old Cora with wife Michaela) Doherty is aware of the strain many families are under at mealtimes. “As a realist and a parent, there are lots of time pressures and concerns, there’s a lot of outside influence and if one kid has something, your kids will want it,” he admits.

They live in Suffolk, and the family loves sitting down forSunday roast with all the trimmings together. Like their famous dad, Molly and Cora also enjoy growing their own food.

“I’m lucky to be in a position where my daughter comes and helps me in the greenhouse and plants seeds and sees them grow,” explains Doherty, 39. “But I think our reliance on someone else to constantly feed us is a slight worry.

“There are only a few large food companies who control most of our food, and I think there’s something very important about going back to tradition and getting our food culture back in order, and that often means looking back to our grandparents.”

It’s not all doom and gloom though. “I think Britain’s an exciting place,” he adds. “The problem with all this stuff is that often, it can be a very negative, finger pointing, ‘You can’t eat that! Blame the supermarkets’. At the end of the day, we’re the ones who are in control of what we eat, we’re not children, we make informed decisions.”

While he hopes the documentary will give the public food for thought, he doesn’t expect his young family to be very interested.

“I think my eldest daughter is much more interested in kids’ TV show Ben And Holly’s Little Kingdom than anything I do,” he says, laughing.

“If I turned into Daddy Pig from Peppa Pig, that would be something,” he adds, “otherwise, my programmes are a bit boring.”

  • World’s Best Diet (Channel 4) Monday.