A Moral Dilemma

Marketing tactics of businesses may involve drastic measures in order to convince their target market that they should buy their products. Sometimes, this may involve false or fake advertising, which means that they will tell a lie, or an untruth about their product in order to sell it. For example, a McDonald's Big Mac that potential consumers see on advertising, may be entirely different from the Big Mac that they buy. 

To what extent can companies go in order to sell their own products without blatantly lying to their consumers?