Many things can have an instant effect affect on your body.
For instance sugar and alcohol are pretty much immediate. I would imagine many chemicals can get right into your bloodstream and therefor your body.
Fat, on the other hand is a fairly slow mover. I takes awhile for your body to break down and it takes awhile for it to be stored.
Being "hydrated" is good, however how much water you are retaining can vary widely depending upon the above chemicals. For example, alcohol and caffiene are both diuretics and you will LOSE body/water weight vs thinking you are "hydrating".
Stephen
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