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Below is the response tweet from Sean McClure(@sean_a_mcclure) to Bryan Johnson (@bryan_johnson) on X

The problem is this:

You have been convinced of 2 things:

1) that biomarkers (outputs) are a sign of health/age, and

2) that since you “know” the outputs you want, the answer to maintaining or improving those outputs is to make the inputs the same (e.g. a healthy body has high X, therefore I will do more of X).

Let us assume that #1 is true. That biomarkers (outputs) are a sign of health/age. This is already highly debatable, but let us assume this is true, and further, that your (and others’) research has identified a very good set of signals for health/age.

#1 being true has almost nothing to do with #2 being true, which in any case, it is not.

The signals the body gives off (when measured) are there for reasons that are nondeterministically connected to its inputs. For example, you can track things like CRP, lipid levels, glucose, IGF-1, etc. which may indeed be indicative of health, but I assure you, you do not know how to arrive at those markers in any deterministic sense.

The body’s regulatory mechanisms are (extremely) nonlinear. It takes zero knowledge of medicine or nutrition to know this, because it is a universally true property of complex systems, and the human body is without a doubt a complex system.

Say you reduce IGF-1 through caloric restriction. Is this healthy? Will this reverse aging / extend lifespan? In some narrow way it might indeed contribute to that end goal, but more broadly it might simultaneously reduce muscle mass and resilience, moving you in the opposite direction. You might artificially prolong telomeres, only to increase your cancer risk. You might reduce your fat intake, only to reduce necessary lipid signaling. You might push excess endurance only to inflict coronary artery calcification.

This is the nature of complex systems. There is no chance the body is not like this.

What you are doing is chasing non-mechanistic indicators of aging, as though they were in fact mechanistic. This is a transgression related to reductionism and false causes.

It is very common for people to do this. It is a problem of misplaced concreteness, which gives people a sense of false control. It seems to logically make sense that if a healthy body shows signs of X (output), that making X happen deliberately (input) can only maintain or improve that output. But this is patently false. Again, this is not how complex systems function.

Imagine the turbulent flow in a pipe. The relationship between input and output is highly nonlinear. The inputs might be a set pressure and velocity entering the pipe, while the outputs might be flow velocity, pressure distribution and patterns at the exit of the pipe. There is very little controlled or predictable connection between the inputs and outputs in this situation. Interactions within the pipe, like turbulent eddies, vortices and branching paths interact in countless ways, leading to complex and emergent outputs that look almost nothing like what went in. The outputs are highly irregular, with patterns determined by the intricate internal dynamics that we had absolutely no control over.

That is just for a pipe; a system far simpler than the human body. If the flow through a pipe lacks deterministic control, consider your human body.

To be clear, I am not saying that human health cannot be improved, as though the whole thing is a crapshoot. Placing oneself into healthy environments and removing modern conveniences from one’s diet is undoubtedly healthy, because it aligns to how we evolved. What I am saying is that your version of control is fallacious and pseudoscientific. You are convincing yourself, and others, that you have a control you do not have. As though age and death is a technical problem that can be approached the way someone approaches debugging a piece of (rules-based) software or steam engine.

It is no different than using drastic social engineering in an attempt to control the outcome. Society is not subject to such control without eventual disaster. The system can always be expected to collapse. Always.