He gave the world the 5:2 diet after investigating the benefits of intermittent fasting. Now Dr Michael Mosley has a new obsession - gut health.
The British scientist and journalist, and host of Trust Me I'm A Doctor, has turned his attention to the workings of the microbiome - the kilogram of alien bacteria that live in your gut.
In his new book The Clever Guts Diet (on sale June 1), and in a special episode of Insight (Gut Feelings, now available on SBS On Demand, or watch it below) Dr Mosley examines how your gut communicates with your body and mind, and explains why your biome affects your weight, your health and your mood.
He says this relatively new area of research is changing researchers' understanding of how our bodies work - and he can't keep the excitement from his voice.
"It is just an unbelievably exciting area," Dr Mosley tells SBS over the phone from his home in the UK.
"It's a bit like the invention of the telescope, suddenly you can see this vast universe that you never knew existed. And it's not out there, it's inside you.
"And when you can do that, scientists get interested because they can measure, they can evaluate and see what's going on."
In our guts live more than 50 trillion creatures, representing at least 1000 different species. Some foods will help your microbiome thrive, while others are the enemy of good gut health.
Dr Mosley says currently there are new studies coming out every week which reveals more about the importance of a healthy gut.
For example, he sites new research which has found that 1 in 100 people have weaknesses in the blood vessels of the brain which commonly leads to stroke, and rather than being a product of genetics as it was assumed, it's actually caused by a chemical produced by bacteria in your gut.
"So you go blimey, why is that happening?" Dr Mosley says.
"But wow, bacteria in your gut causing stroke, I mean who would have believed it?"
Dr Mosley says it is also clear that gut bacteria has a profound effect on mood.
He references an Australian study from earlier this year which found that eating a Mediterranean diet can help treat depression, and the researchers believe that is probably because of the impact on the gut bacteria influencing the brain.
"So they've got a whole new branch of medicine, psychobiotics, which is about the brain/gut axis," he says.
"This thing didn't exist two years ago, and suddenly - bang!"
While Dr Mosley doesn't do original research - "I'm not a scientist, but I do talk to a lot of scientists" - his wife Clare Bailey is a GP who is seeing first hand how diet and gut health can improve the lives of the patients she sees.
"She's started to use food to help her patients that way, and she says it's been one of the most rewarding things of her career," Dr Mosley says.
"She's helping people with type 2 diabetes, irritable bowel and things like that, and she says it's just astonishing how much difference it makes.
"The assumption is this is just going to target the elite and nobody else is going to pay attention, but her patients are generally a deprived, poorer sector of the UK population, and she said they get it, they grasp it, they want to do something about it. So I write these books but she actually puts it into practice."
Dr Bailey has also provided most of the recipes in the new book, which her husband and their four children have all been enjoying at home.
Dr Mosley says he is now convinced that many common gut conditions are better treated by a change in diet - such as adopting the Mediterranean diet, eating a wider range of foods, and including fermented foods - than by using drugs or antidepressants.
"[We're] realising just how amazingly powerful this thing inside you is, what it does, how it touches on so many aspects of your life in ways that we could never previously have imagined," he says.
"I feel the same way [as] when I did the film about 5:2. This really is going to be big, and it really is going to make a huge impact on a whole range of things."
The Clever Guts Diet by Dr Michael Mosley with Tanya Borowski and Dr Clare Bailey (Simon & Schuster Australia, pb, $29.99) is on sale June 1. Catch Michael Mosley in the Insight special Gut Feelings - watch below or on SBS On Demand, as he joins the show to talk about gut health and the microbiome.