Answer :The glycemic index measures how quickly carbohydrates enter the bloodstream as sugar; glucose (sugar) and white bread are at the top of the 100-point scale. Susan B. Roberts, PhD, director of Tufts HNRCA Energy Metabolism Laboratory, who has studied the glycemic index and weight loss, says, The glycemic index is actually quite a laborious method, so differences in glycemic index between two similar foods like this have not really been assessed. My best guess is that the 100% whole-wheat is better, but if the added-fiber pasta has a lot more added fiber that may be fine, too.
Though these specific options werent tested, extensive glycemic-index measurement by scientists at the University of Sydney, Australia, in 2008 showed wide variation between types of pasta. Results varied between similar products from different countries and those made from different wheat varieties. Some whole-grain pastas actually had higher glycemic-index scores than processed-grain pastas. Given the vagaries of such measurements, its probably best not to worry too much about specific numbers when picking pasta. Look for whole grains (see page 6 in this issue), which retain more of the grains original nutritional value, and plenty of fiber, and go easy on the sauces.