Why low carb?

I learned this simplified in nutrition class. Think of the food you eat like a fire. Carbs are like newspaper, protein is like kindling and fat like a log. The newspaper burns first for energy so you body wants to use it first, protein burns up less fast and fats are harder and take more energy to burn. HTH.

Thanks everyone for the replies :) I am in maintanece right now. I did limit my carbs for about the 1st year but started adding a little bit more carbs to my diet after I've reached my goal. 

I haven't gained any weight back, so I think my diet  plan is going well so far. I can see how it would be a trigger. It doesn't seem to be with me. I eat a whole food, sugar free diet (I dump on more than 10g of sugar).