An important concept when considering carbohydrate digestion is not just the type but also the amount of carbohydrate consumed.
The larger the portion of carbohydrate the higher the rise in blood glucose and insulin levels. A small amount of carbohydrate even if it is high GI will not raise these significantly. So just because foods like mashed potato and white bread are very high GI foods – it is the amount you have that will dictate the insulin and blood glucose response.
When a food’s GI is taken into consideration with the amount of carbohydrate consumed this is termed the Glycaemic Load. This is a precise tool to use when seeking to benefit from a low GI diet. Some high GI foods such as watermelon, pumpkin and turnips may be quickly absorbed but the actual content of carbohydrate per serving is low because much of the food is made of water. Thus these high GI foods, like most fresh fruits and vegetables (with the exception of potato) have a low Glycaemic Load so you don't need to avoid them.
So with the added benefit of plenty of nutrients and fiber, you do not need to be concerned with their high GI. Simply this means when it comes to carbohydrates and a healthy weight it is not just what you eat but how much. A helpful rule can be to limit your starchy carbohydrates (e.g. rice, pasta, root vegetables) to one quarter of your dinner plate or at other times a handful is a good indicator of a portion size. The exception is at breakfast time where your carbohydrate stores need a big boost (see breakfast guidelines).