When and how often you eat are just as important to your energy levels as what you eat. Long periods without food tell our bodies to shut down and conserve energy.
That fact has been programmed into our DNA, and it makes perfect sense when you think about it.
In the days of Neanderthal Man, food was more scarce. For early man to survive during winter time or periods of food scarcity, the body's metabolism would slow down dramatically in what you could call "survival mode".