A scientist tested 15 longevity hacks. 3 weren't worth the money, including a gut health test.

• John Tregoning, 47, tried 15 longevity hacks to see which ones were worth buying.
• The research scientist tried things like cold water swimming, gene sequencing, and blood analysis.
• Calorie restriction helped him lose weight, but he missed out on social activities.

As he entered his mid-40s, it finally hit John Tregoning that he was going to die one day.

Faced with his mortality, the vaccine immunologist based at Imperial College London, wondered if there was anything he could do to extend his lifespan (unlikely, he thought), or at least live healthier for longer.

He researched buzzy longevity treatments that he hoped would prevent conditions such as cancer, type 2 diabetes, and cardiovascular disease, which are leading causes of death.

He landed on trying: gene sequencing, whole-body blood analysis, an ECG, more exercise, cold water swimming, eating beetroot, eating less salt, Dry January and alcohol replacement, eating less red meat and more vegetables, brain training apps, sleeping more, a calorie restriction diet, eating more fiber, microbiome sequencing, and drinking more water. He documented his experience in his book "Live Forever? A Curious Scientist's Guide to Wellness, Ageing and Death."

Tregoning shared the three longevity hacks he thought were a waste of money.

Microbiome testing

The gut microbiome is the name given to the trillions of microbes that live in the colon lining. A gut microbiome with a diverse range of microbes is linked to better overall health — from the immune system to the brain.

Understanding how it works and impacts the body is a large area of research, however, there is still much scientists don't know, Tregoning said. But this hasn't stopped businesses from cashing in on the hype and selling products claiming to support gut health, he said.

Microbiome sampling, which involves sending your poop off to a lab to be tested, has become a readily available, albeit pricey, service. Most tests go for between $200 and $300.

Tregoning sampled his gut microbiome after making dietary changes on three separate occasions, to see if the results might help him make some gut-friendly changes to his diet.

The first sample was taken when he followed his typical diet, the second after he ate a curry and drank two bottles of beer, and the third after he ate 30 grams of fiber and three portions of fermented foods for a week, based on advice from a GI surgeon and researcher colleague.

The results showed that his microbiome had changed after the high-fiber week, but it had also unexpectedly become less diverse. A new type of bacteria had entered his microbiome, but the test couldn't tell him what that might mean for his health.

Tregoning said that the results were not useful because they weren't actionable, and only reflected the state of his gut at very specific times.

"Saying that this one bacteria in a sea of bacteria changes anything, we are nowhere close to that," Tregoning said. "It's a single snapshot. It's a bit like saying, 'How do you feel this second?' It changes all the time.

Calorie restriction diet

Calorie restriction, either through eating fewer calories or intermittent fasting, has been shown to extend the lifespan of mice. It can also help people who are overweight or obese reach a healthy weight, which can have beneficial knock-on effects for their health.

As part of his research, Tregoning tried a fast-mimicking diet for five days. He purchased a diet kit for £160 ($207), which came with packets of soup, nut bars, kale crackers, olives, and chicory root bars, which would provide him with 900 calories a day.

He lost more than six pounds in that week and kept it off for a month, but overall he didn't find the diet sustainable.

"It was effective in terms of I lost weight, but I was pretty listless and miserable for the whole week," Tregoning said. He wouldn't do it again mainly because it was too expensive and he largely had to stop socializing to follow it.

"It really pointed out to me how central food is in my life socially. In cooking with friends or cooking for family, having lunch at work with people, there's lots of social elements around food, which in that week I was missing out on," he said.

Social connection is crucial for longevity, and social isolation accelerates decline, healthspan, and lifespan, Trengoning said. This aligns with longevity research, which has found relationships to be as important for health as factors such as diet and exercise.

Gene sequencing

To assess his risk of developing certain health conditions, Tregoning did a genetic test.

He ordered a kit from 23andMe, which revealed that he doesn't have the gene variants for any of the 46 traits they measure or any of the 14 genes that make a person predisposed to a range of diseases, including breast cancer (BRCA2), Parkinson's disease, and age-related macular degeneration.

It also told him more trivial things like how likely he was to have back hair, and that his genes were likely 2% Neanderthal.

Overall, Tregoning did not find it a useful exercise. "It's fun, but it didn't really change anything in my understanding of what my personal risks are," he said. Our genes predicts likelihood rather than actual outcome, he said, and they are influenced by environmental factors and lifestyle.

"Environment is as important as our genes. The phrase I like is 'genes loads the gun, the environment pulls the trigger," he said.