The most common cause of disrupted sleep is blood Sugar imbalance or hypoglycemia.
When blood Sugar falls too low in the middle of the night, your adrenals kick to give your organs energy (that'd you normally get from having a normal, maintained level of blood sugar.)
When you fix your diet, this MAY resolve.
Best books I know on diet are:
1.) "Living Low Carb" by Jonny Bowden - read the first half of this for information about how insulin works. Then it reviews a bunch of low carb diets. The one that worked for me was Schwarzbein Princple II, a low-medium carb diet that includes reasonable portions of grains. Following it greatly reduced my waking up in the middle of the night issues.
2.) "The Schwarzbein Principle II" by Dr. Schwarzbein