Deep in the brain, near the floor of the skull is a region called the hypothalamus. Within this structure are regions devoted to controlling your biorhythms. You wake up each morning and go to bed each night according to the rhythm generated within this brain region.
The way the brain knows when to do these things is partly influenced by the amount of sunlight entering your eyes. The rising sun wakes you in the morning and your brain responds to this signal by telling you to eat breakfast. Your entire day is orchestrated by the rhythms generated within this brain region. Needless to say, if you interfere with the rhythms of your body the consequences can be significant and often unpleasant.
Recently, a study was published Dr. Randy Nelson in the prestigious journal, The Proceedings of the National Academy of Science, outlining how the time of day that we consume food influences whether we convert the calories into nutrients or fat. The study suggests that if we eat late at night, outside our normal diurnal feeding cycle, we are more likely to convert our calories into fat and also impair our ability to regulate blood sugar in response to eating. This last condition is known as diabetes; nighttime eating has previously been related to the development of diabetes in humans.