Starch is nothing more than glucose (blood sugar) molecules that are bonded together into very long chains. Unlike sugar, starch does not dissolve in water and it does not taste sweet. However, starch is rapidly digested into glucose when it enters the gut after eating. In fact, potato starch and some white rice can actually cause your blood glucose levels to rise faster and higher than can glucose syrup. To put it another way, many starches have a very high glycemic index.
High Glycemic-Index Starches Can Harm Health and Contribute to Obesity