When we consume food, our blood sugar levels begin to rise, since the food we eat is broken down into a sugar called glucose, which can be turned into energy. However, glucose cannot be turned into energy until it enters the cells. Insulin is created and released by the pancreas and it allows cells to take in sugar (Glucose) from the blood. This slowly decreases your blood sugar levels back to normal. When your blood sugar levels are too low, your body might signal you to eat something (tummy rumbling etc.) and the process repeats again.
hopefully, this helps. :)