Just to add my own little tuppence to what is now a fairly old conversation, I certainly find that whenever I have periods of eliminating things from my diet which I might perhaps overindulge in sometimes

then I definitely notice a physical effect. This is definitely true of alcohol, but I also notice it in things like caffiene, chocolate etc - all of the stuff that you might ditch for a while by way of a little detox. A couple of days later the 'transition' might be gone and I get on with feeling healthy and smug!