Not to nitpik this, but I don't consider eating off the dollar menu at McDonalds anyway to save money. In the long haul--that's probably what will end up killing you or at least racking up some medical bills. I'd rather spend 10x the dollar menu at a local lunch spot with real food that won't send me to an early grave.
All around, good advice--but don't use fast food as a way to slim down the budget.