SENS vs. Metabolic Anti-aging Strategies

Strategies for treating or preventing age-related diseases can be broken down into three broad categories:

slowing production of metabolic byproducts which eventually accumulate to pathogenic levels (Treatment "A");
treating diseases after symptoms arise, or at least long after precursor damage starts (Treatment "B");
addressing metabolic byproducts before they reach a pathogenic level.

(Flattened arrows imply impedence.)

Examples of Treatment "A" include exogenic antioxidants, hormone supplements, resveretrol, caloric restriction, and "longevity genes" to turn on or off.

These three approaches have been compared to maintaining a house that gets holes in the roof:

slowing damage to the roof by planting trees for wind protection;
addressing chronic damage inside the house from rain coming through the roof;
repairing holes in the roof as they come up.

Putting it in home maintenance terms helps clarify why the third approach may be preferable to the other two. All three offer benefits, but repairing the roof whenever it is damaged requires less frequent intervention than having to address damage in the house after every rainfall. And planting trees only slows the rate of roof damage.

Likewise, addressing metabolic byproducts before they reach a pathogenic level has its advantages over Treatments "A" and "B".

To extend the house analogy further,

despite the wind protection, the roof will still deteriorate, just at a slower rate;
the trees themselves could fall and damage the roof (or more);
repeated use of tree protection leads to loss of view and reduction of enjoyment of the house;
there are other ways a house can deteriorate.

Likewise, Treatments "A" such as antioxidants, caloric restriction, etc.

at best slow the rate of age-related deterioration, if at all;
have unquantified risks of long-term side-effects;
must be partaken on a regular basis;
each only do a partial job.

To elaborate on the last point further, they not only do only a partial job in that they merely slow the rate of deterioration, but also in the sense that each leaves other molecular/cellular precursors of age-related pathology unaddressed. For example, hGH injections could help with replacing lost cells, one of the seven pillars of SENS research, but doesn't address lysosomal dysfunction, degrade protein crosslinks, defend against genetic mutations, or address the toxicity of senescent cells.

To borrow from the above-linked paper by Aubrey de Grey:

The tiles are the fulcrum of the process by which weather wrecks the house: not too early in that process, not too late, but just the point where a scrap of timely, judicious action can pre-empt all that otherwise follows. In aging, the same logic applies. Rather than trying to stop damage (at the molecular and cellular level) from happening in the first place, a more practical strategy to prevent damage from snowballing out of control is letting it happen unhindered and repairing it periodically.