The basic process that occurs when you eat: you eat a food, it eventually gets into the stomach, while you are digesting the food your body carries the glucose into your blood stream.
Now you have a whole bunch of glucose (AKA blood sugar) floating around in your blood stream. The liver goes "Oh my goodness, we have to get this glucose into the cells!" So it does it's job and releases insulin into the blood stream.
BIG NOTE: In order for glucose to enter into cells IT MUST HAVE INSULIN. Insulin is the key that lets glucose enter your cells door.
Once insulin and glucose match up, they enter into the cell. Eventually all the glucose is in cells and your blood stream has NO GLUCOSE- AKA no fuel!
This is when you're body signals to you that you are hungry. It hopes you will eat again and the process continues.
Problem: When you eat high GI (glycemic index) foods, it causes the amount of glucose in your blood stream to RISE RAPIDLY. That means your liver freaks out and shoots out tons of insulin. Remember its goal is to get all that glucose into cells.
Well, you had no glucose in your blood stream, then you eat a high GI food, glucose floods the blood stream, liver shoots out insulin, glucose is quickly shoved into cells, now there is no glucose in the blood stream, you're hungry again...
A rapid rise in glucose means a rapid fall into hunger again. Ever eat a bowl of fruit loops for breakfast and be hungry an hour later? That's because just eating processed or higher GI carbs means a fast digestion.
You end up eating more calories because you always feel hungry.
The trick: eat lower GI carbs (most fruits, veggies, unprocessed foods) WITH a protein source. This combination provides a even supply of glucose. The liver can handle it and there are no rapid rises/falls in your blood sugar levels.
Eating a protein/carb meal also slows digestion to a 2-3 hour window. This is why it's recommended you eat every 2-3 hours.
Sorry if this makes no sense, but the basic idea here is to eat un-processed foods as much as possible. Better food choices include fruits, veggies, potatoes, brown rice, sprouted wraps, lean animal meats, soy based foods, etc.