As a boy, Professor Sinclair spent a lot of time at Mirrabooka in the lake's south-west.

Asked how he recalled that time, he said: "Oh, the best".

"We had a little dinghy with a 15-horsepower motor. As a young teenage kid, having that freedom to go fishing, sailing, windsurfing - that's a life that I really miss," he said.

Professor Sinclair works at the Department of Genetics at Harvard Medical School. He's Australian and grew up on Sydney's northern beaches.

"I'm here in Boston and the water is freezing cold. You don't go windsurfing unless you're insane. I did buy a house on the water to try to recreate that life for my kids, but it's just not the same as being on a beautiful, warm, flat lake."

In 2014, Time Magazine listed him among the "100 Most Influential People in the World". In 2018, Time listed him in their top 50 people transforming healthcare.

The reason is his work on longevity. He was due in Newcastle in early April to attend the Newcastle Writers Festival to discuss his recently released book, Lifespan: Why We Age - and Why We Don't Have To.

Professor Sinclair believes ageing is a disease. Not only that, he believes ageing can be put in remission and that age-related diseases can be prevented and reversed.

"I don't want to cure ageing. That's not what I'm trying to do. I'm trying to keep people healthier for as long as possible - to improve the body's defences against disease," he said.

He has called for greater international attention on the social, economic and political risks and benefits of a world in which billions of people can live much longer and much healthier lives.

He's working on medicines that enable people to live healthier for a longer time.

And he's more than happy to use himself as a guinea pig. The results are impressive. Blood tests show his biological age is much lower than his real age. His father - who is in his 80s - is also showing remarkable results from his anti-ageing regimen.

"Right now medicine is able to treat diseases once they occur, which is often too late," he said.

"I call it whack-a-mole medicine. Our approach has been to find the body's defences against the ageing process."

He's concerned with what makes people sick in the first place.

"Young people don't get heart disease or Alzheimer's. There's a reason for that.

"If you're not sick and you stay healthy, you tend not to die."

The professor has spoken about his personal anti-ageing regimen, which includes taking supplements and drugs called NMN, metformin and resveratrol [which occurs naturally in small doses in things like red wine and blueberries].

His research shows that resveratrol should be taken with some fat to be properly absorbed. He mixes it with yoghurt.

"I'm definitely not the kind of person who says go and buy a supplement. I'm not selling anything. I don't want anything to do with supplement companies," he said.

Asked the cheapest way to seek longevity, he said: "Eat less often".

Of course, this doesn't mean starvation or malnutrition. But he is a proponent of intermittent fasting.

"The idea of always being satisfied is very 20th century. The 21st century is where our bodies need to be put in a state of adversity, call it hormesis," he said.

"It basically means that if we're never hungry, we're never moving and never out of breath from running, our bodies don't bother being strong. They become complacent.

"We found the genes that underlie those processes. We've got seven of these genes. They're called sirtuins. They turn on the body's defences against ageing and the diseases that come with that."

He said people can eat less often, exercise and eat the right foods to help ward off the diseases of ageing. But more people will increasingly have the choice of taking medicines and supplements that artificially turn on the affected genes to give the health benefits, without necessarily having to do the required levels of exercise and proper eating.

Professor Sinclair appears to have a long life ahead of him. And he loves to return to Australia.

"I come back any excuse I can get," he said, adding that he hopes to one day attend the Newcastle Writers Festival when the world returns to normal.

You know you're getting old when: Everything that works hurts, and what doesn't hurt doesn't work.

You feel like the morning after and you haven't been anywhere.

Your children are beginning to look middle-aged.

You look forward to a dull evening.

Your knees buckle and your belt won't.

Your back goes out more than you do.