The key reason why the quest for eternal health and life is as futile as the quest for Eldorado was, is a simple law of physics: The 2nd law of thermodynamics tells us that every living system inevitably moves along a path of progressive functional decay until the point of complete loss of function (death).

This degree of functional loss is called entropy Living systems are unique in that they have repair mechanisms in place which throw out some of the entropy, that is, replace or recycle dysfunctional cells and their debris. While that reduces entropy it never eliminates it. After all, the repair mechanisms themselves are subject to the 2nd law, too. I have explained this in greater detail in an earlier post about Bryan Johnson's experiment.

From a science point of view, I find his experiment interesting. If he continues to honestly and openly share his data, we might learn something from his single-case experiment. How much of it is translatable to others will be a matter of debate.