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

John Tregoning tried a diet with restricted calories but it wasn't sustainable.

John Tregoning/ Getty Images

• 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.