At the end of the experiment, tests on some of the volunteers revealed extraordinary changes in their biology. Their blood pressure, insulin sensitivity, blood sugar control, cholesterol and levels of inflammation had all markedly improved. Underlying health issues had been resolved. It turns out that eating slightly less, but increasing the quality of the food, is a more potent way of slowing ageing than any drug. So for two months I tried to do the same, limiting myself to a strict 2,100 calories per day, a significant drop from my typical 2,700.

I excluded all highly processed foods, refined carbohydrates and sugar, and focused on nutrient-dense alternatives. Spelt was in, as were nuts, seeds and dried fruit for snacks, lean meats such as chicken and lamb, slow-cooked dinners and broths. My partner and I became particularly fond of making Vietnamese pho, featuring chicken, beansprouts and ample herbs. I usually consume alcohol moderately, maybe a glass of wine on Fridays, so I didn’t make any changes there, but I did start drinking two or three daily cups of green tea, a beverage packed with flavonoids. These plant chemicals have been shown to be particularly good at helping the body to shed damaging internal or visceral fat, as well as toning the health of blood vessels, making us more resilient to hypertension.

It wasn’t easy to begin with. For a week I was plagued by sugar cravings and the persistent sensation of a hole in my stomach, but within a fortnight it had become more or less routine. By the end of the two-month experiment, I felt better: I had more energy, was better equipped to cope with stress, and felt mentally sharper. While I’d shed 6kg (nearly a stone) and felt noticeably trimmer, the most significant changes were internal.

Before and after the diet I visited the University of Birmingham, where tests showed that my levels of inflammation and visceral fat had plummeted. I took a blood test that measured 12 metrics of immune health, ranging from the number of new white blood cells being generated to the number of inflammation-suppressing cells. The results revealed that my “immune age” had reversed by approximately two years.