Can a high-carbohydrate diet cause diabetes?

I know that carbohydrate will be converted to glycogen (sugar) and stored in body. For this reason, if I eat a lot of carbohydrate, ie. the food groups at the base of Pyramid Food Guide, will I possibly increase sugar for myself? ANd consequently, will I have diabetes because of high-carb diet?
: I eat a lot of high-sugar fruits too though, eg, grapes, tangerine, pears, apple. My diet is low around 1,200-1,500 calorie and my eating habit is irregular.

And if I exercise regularly, will my sugar decrease due to burning of energy for use during exercise?