Food is needed by our molecular machinery for two reasons: energy and parts. Parts to be used as building-blocks for making more machines, and parts needed as plug-in subordinates for machines so that they can carry out a particular function.
Water is the most common example, partly because of its lubricating dance round the machines and partly because it is needed for their operation in ways we have yet to discover.
Food can therefore be seen as logical input, some of the 'premises' upon which the processing of logical devices work for the functioning of the organism.
The input, processing and output are the logical necessities of life.
If, if and only if the premises are true and the reasoning is true will the conclusion be true. So long as premises and reasoning remain true, life is the conclusion. When they fail to be true the conclusion ceases to be life.
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That means the old adage, 'Feed an illness', can be seen as beefing up the logical input in order to process the logical anomaly out of the organisam. It is rather like tracking down and prosecuting a criminal in order to get him out of society--more input from the police, the lawyers and the courts is needed.