GI (Glycemic Index) is a measure of how quickly carbohydrate effects your blood glucose... Glucose (the purest form of carbohydrate) has a GI of 100.. other food is then ranked between 0 - 100 depending how quickly it will increase your blood glucose... In general hi GI foods are processed quicker by your body and cause your blood glucose to rise higher.. they also don't satisfy your hunger for very long... they are good foods for energy replacement post exercise for instance...
As a diabetic you want to avoid high blood glucose as this will cause you damage.. prolonged high blood glucose will lead to diabetic complications such as; blindness, amputation, loss of sensation, kidney failure, heart attack (you get the picture)....
Hi GI foods (70+) include: white bread, rices and pasta... breakfast cereals, sweets, chocolate, etc...
Medium GI foods (56 - 69) include: whole wheat products (breads, pasta, rice), root vegetables (such as baked potatoes)
Low GI foods (55 or less) include: most fruits and non root - vegetables, legumes/pulses, nuts, beans, beets, chick peas, etc..
Note: Generally the longer you cook pasta / rice or vegetables the higher GI they become as you break down the starch... this makes it easier for the body to release the glucose
Ideally you want to start replacing the 'white' high GI foods with medium / low GI foods.. these take longer to digest and will keep your fuller... You may also consider reducing your carbohydrate intake and replacing it with proteins / fats... less carbohydrate in your diet will improve your blood glucose control.
Protein can be found in meat (especially chicken and fish) it is also found in a lot of pulses and beans... vegetarian products such as Quorn are also a good source..