You might already know that the rate at which your fingernails grow can reveal how quickly you’re ageing, as can your gait speed.

There’s good news, though ― a recent study involving roughly half a million members of the UK’s Biobank found that 23 of the 25 environmental factors associated with longevity are “potentially modifiable.” 

These include how often (or whether) we exercise, and whether or not we smoke. 

And in a recent interview with CNBC’s Make It, Dr Valter Longo, Professor of Gerontology and Biological Sciences and Director of the Longevity Institute at the University of Southern California, who’s studied longevity for the past 36 years, said that diet may impact how long and well we live too.

What are his diet rules?

The gerontologist says: “Some dietary interventions are much more powerful than we had imagined” for keeping us healthy for longer.  

For his part, the expert follows these rules:

1. A “fasting-mimicking” diet, which involves not eating for a 12-hour window ― “You eat, say 8 am to 8 pm, and you fast 8 pm to 8 am”, Valter says.
2. Using mainly vegan ingredients for his meals. 
3. Eating a lot of vegetables, but not as many fruits. 
4. Eating whole grains like oats and brown rice often. 
5. Having fish three to four times a week. 
6. Eating tree nuts, like cashews and Brazil nuts.
7. Eating legumes, like chickpeas and beans. 
8. Not eating more than the recommended amount of protein. 
9. Eating “very little cheese”.

These recommendations are based partly on some evidence that suggests eating within a time “window” is linked to a longer, healthier life. 

The other advice is inspired by the diets of people who live in “blue zones,” where individuals seem to have longer lifespans.

These include the food habits of those from Okinawa in Japan, and the Mediterranean.

Are there any other ways to boost longevity?

While a lot of the research into longevity is exciting, the recommendations experts like those at Harvard can make based on existing evidence are perhaps reassuringly dull and well-known. 

Eating well, exercising enough, avoiding smoking, not drinking too often, and getting enough water can all help, the university shared on their health site. 

Still, even among that advice, some unexpected gems emerge ― for instance, it turns out that socialising more often and staying optimistic can have a meaningful impact on your longevity too.