Glycogen is the storage form of glucose that's needed by the central nervous system as fuel. Your brain turns burns glucose for energy, excess is converted to glycogen which fuels you through the day, and amounts ingested in excess of that are converted to fat. So he was wrong to say that the foods contained glycogen, but correct to say your brain burns it.
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A gentleman should always be able to break his fast in the manner of a gentleman where so ever he may find himself.--Good Omens