Fruits and vegetables contain soluble and insoluble fiber in varying proportions. When you eat soluble fiber, it absorbs water to form a gel-like mass, which helps you feel full and provides other health benefits. It prevents a surge in blood sugar after you eat by slowing down the absorption of carbohydrates.
If the blood glucose level falls to dangerous levels (as in very heavy exercise or lack of food for extended periods), the Alpha cells of the pancreas release glucagon, a hormone whose effects on liver cells act to increase blood glucose levels.
The liver is supposed to release small amounts of glucose when you're not eating. But in type 2 diabetes, the liver dumps more glucose than is needed into the bloodstream, especially at night. So, while your hormones are causing a natural rise in blood glucose, your liver is releasing even more sugar into your system.