I have rich older relatives and they essentially do this already. It has, unquestionably, added years to their lives. Scaling it to >90% of the population will be the work of the next 30 years, but the tech is there. The money isn't, yet.First, everyone who is alive (or at least over 90% of the population) will have high quality, regularly scheduled medical attention. Basically a yearly checkup for everybody, take basic vitals, in addition to some blood, and a few other samples. These massive, population-based samples get screened for everything. Take every number and fact that can be squeezed out of those samples, and combine it with their personal history (Socioeconomic status, family status, intelligence by some measure, level of education, level of parents education, list goes on), to create a biological model of the entire human population.
Not only years, but quality in those years. In Brave New World, Huxley talked about sex-hormone chewing gum, among other things, as a commonality in his dystopia where no one aged, right up until they died. I suspect we'll have quite a while where at least a portion of humanity lives like this, and I wouldn't be surprised to see food with intentional hormonal additives within the next few years. We already have labels on our food telling us about its health benefits or 'health benefits,' how long until we're exactly formulating the composition of our bodies? We'll live in near perfect physical/mental health, until the Hayflick limit takes us. (And if Aubrey de Grey gets his way, we'll do away with the Hayflick limit too) Better living through chemistry, we're all just olympians in the making.