Here are few basics of a healthy diabetic diet, you need to find out from nutritionist how many calories and carbs your father can have per meal and snack. Whole grains, fresh fruit and vegetables, lean meat and poultry. Stay away from the white stuff as much as possible, sugar, white bread, white potatoes, white flour, white rice etc. The less processed and closer to nature the food the better. Whole grain breads, whole grain wheat flour, brown rice and sweet potatoes are healthier choices.