Not all starchy foods release glucose (sugar) into the blood stream at an equal rate... This is the reason for feeling hungry sooner, after eating two slices of toast for breakfast, than after eating High Fibre Bran or Fibre Plus and milk.
One way to control fluctuations in blood sugar levels is by consuming low-GI carbohydrates. The GI is an index with which carbohydrate rich foods are measured assigned on a scale from 0 to 100 which also reflects their influence on blood sugar levels.
Low GI foods cause slower rise in, and more sustained sugar levels. Foods with a GI of 0 to 55 are known as low GI foods, those with a GI of 56 to 69 are known as intermediate GI foods and foods with a GI of 70+ are known as high GI foods. Sugar free food doesn't necessarily have a low GI rating and not all foods that contain sugar necessarily have a high GI rating.
For this reason all carbohydrate foods are tested on real people in order to calculate their GI. Foods with a low GI rating are viewed as fat burning foods and will provide you with a satiated feeling for longer. In this way, insulin levels stay lower and your body burns more fat for energy, which is not the case when insulin levels are high. Therefore foods with a low GI rating are preferable.