The most talked about topic concerning our obesity epidemic involves two major theoretical theories: the conventional theory of calories in -calories- out and the carbohydrate-insulin model. It is important for the population to have a basic understanding of these theories in order to deal with the obesity conundrum so prevalent in our current food environment. Determining which is predominant could help us to counteract the epidemic with the most effective dietary treatments. The following article provides us with a simplified understanding of both sides of the debate.