Why are low carb diets typically unsuccessful in the long term?

Carbs are your body's main source of energy, so cutting off your carbs is like expecting a car to run as fast on less gasoline. Instead of cutting yourself off completely from them, you should eat more complex carbs, such as whole wheat (not just whole grain) in bread, rice, or cereal. They also keep you full longer so that you don't indulge in fatty snacks.