ABSTRACT
Explaining the Caloric Restriction E‚ect within the Disposable Soma €eory One of the most popular and frequently-cited evolutionary theories of aging is based on the body’s energy budget. In the Disposable Soma theory [4], reproduction, repair, and current metabolic needs all use food energy. With limited caloric resources, the body is evolved to compromise in allocation of energy and the portion for repair/ maintenance functions is subordinated to uses that offer a more immediate payoff. On its face, this theory would seem to predict that decreased caloric energy would lead to a harsher compromise, with less energy available for repair. Thus the Caloric Restriction response predicted by the Disposable Soma (DS) theory is opposite to the one observed. Such a basic predictive failing should be considered a fatal flaw for the DS theory. This point has been ignored in a great body of literature based on DS reasoning. The first attempt to reconcile DS with CR came from Holliday [69], who proposed that caloric restriction extends lifespan via curtailment of reproduction as an essential intermediary. Energy savings from shutting down reproduction are so great as to more than compensate for the lower calorie intake and thus more net calories are available for repair when fewer calories are consumed. This theme was picked up by Kirkwood himself, in a strained attempt to make it work quantitatively [23, 70]. But, in contradiction to the positive spin provided in the discussion and abstract, the Shanley/Kirkwood model demonstrates clearly what our intuition tells us is true: fewer total calories consumed translates to fewer calories for repair. The severely limited scope of this model was demonstrated in a rejoinder article [3]. I offer more details of this and other failings of the DS theory in Chapter 4.
