[somenameforme]

The ultimate thing he's testing is not whether this drug or that can extend life expectancy by a few percent, but whether a complete lifestyle regime can indefinitely defer aging. The answer to this is almost certainly 'no', but if somehow he did succeed then confounding variables outside of his regime are not going to play a factor, because it's something far away from what anybody has achieved. And so at that point you'd be able to see 'okay, this does work' and then try to minimize it down to isolate the most key causal factors. And the mountain of data he's collecting in the interim would provide a huge head start on that.