A few years ago, Marc Provissiero, a movie producer approaching his mid-50s, started contemplating the next decades of his life. He joined a high-end longevity clinic for a few hundred dollars a month and began monitoring his blood panels, eating better and improving his sleep. He wanted to stay active as he aged – playing tennis, surfing, hiking and spending time with his young daughter.

But during Provissiero’s annual physical at the longevity clinic, his physician, Dr Darshan Shah, gave him a sobering warning. Despite his healthy habits, Provissiero’s blood sugar was nearing prediabetic levels. A family history heightened his risk of developing diabetes, which can shave years off a person’s life expectancy. When a stricter diet and exercise regimen did not move the needle, Shah prescribed metformin.