Apparently this is a reason to feel like shit, according to this site. If you feel crap after only 4 hours since your last meal, quit eating so much sugar and eat decent food that keeps you filled and energised for a while. In fact, I reach my peak productivity at least 4 hours after a meal, when my body isn't spending much energy digesting food. Have you ever experienced the mental clarity of 12 or 24 hours of fasting?
The idea that we need to eat many small meals is such a Western, privileged world wife's tale that keeps being repeated. We're designed to function and hunt after some prey after days of starvation. We're not designed for the modern blood sugar seesaw. Not eating for 4 hours isn't gonna kill you, and if it is, stop eating Mars bars for lunch, and ingest some proper food.