One of the most successful anti-ageing strategies ever discovered is caloric restriction. It requires a permanent cut in energy intake of up to 60 per cent. In every experimental animal that has been put through this, from fruit flies to primates, it extends lifespan and healthspan (the number of disease-free years at the end of life).

The strategy works because it switches on an evolutionary adaptation to starvation, which prioritises repair and survival pathways over growth and reproduction. Calorie-restricted animals tend to be leaner, fitter, metabolically healthier and mentally sharper than those that eat at will. They also have a stronger immune response.

Unfortunately, caloric restriction is extremely hard to maintain voluntarily. But there are ways to mimic it without going on a permanent starvation diet. The key is to deactivate a nutrient-sensing pathway inside cells called mTOR. When calories are scarce, it switches off, initiating the metabolic cascade that transitions your system into famine mode. The pathway can also be toggled off with drugs called mTOR inhibitors, the best-known being rapamycin.

Some people self-medicate with rapamycin even though it isn’t officially recognised as an anti-ageing or immune-boosting drug. There are other ways to achieve mTOR inhibition though. One is intermittent fasting, a temporary state of caloric restriction that is enough to switch off mTOR for a short while and still obtain its benefits. There are various regimes including the 16:8 diet, which involves completely eschewing calories for 16 hours and only eating in an 8-hour window. Even done once a week, this is an effective way of slowing aging, strengthening the immune system.

Exercise and keeping your weight down are also a proven mTOR inhibitors.  Aging is associated with a decline in the function of the immune system’s B-cells and low production of antibodies in response to vaccines.  So is being obese, which is associated with poor vaccine response, even in people who are young.( New Scientist, March 29, 2020)