More Fat Equals Lower Blood Sugar

Nice summary from Healthy Diets and Science:

Diet 1 consisted of 55% carbohydrate, 15% protein, 30% fat

Diet 2 consisted of 20% carbohydrate, 30% protein, 50% fat

After 5 weeks:
The high carbohydrate diet produced blood glucose levels of 198 mg/dl
The low carbohydrate diet produced blood glucose levels of 126 mg/dl