What causes obesity? You can see there is a very long laundry list. If you wanna really sum it up, it's really essentially one concept. It's ancient genes in a modern environment. In the old days, being able to hold on to our calories was a good thing, when we didn't have a lot of food around. Now in the modern environment, when we have so many food available, not so good. Cause we will really cling to every last calorie. The other thing that is going on is we know that physical activities declined, and believe or not, sleep may play a role too. And you may know this, if you don't sleep a lot, the next day when you get up, where do you get your energy from? A cup of coffee or more food? So all those things come to play.

John Morton is an associate professor of Surgery.