The glycemic index, or GI, measures the speed at which the body digests the carbohydrates found in food. The higher the speed, the more a food causes a spike in blood sugar. A diet rich in high-GI foods, those with a glycemic index of 70 or more, correlates with many health problems including obesity, diabetes and heart disease, according to the Harvard School of Public Health. A food item has no GI value if it lacks carbohydrates.
Highly processed carbohydrate-rich foods -- such as grains whose fiber has been stripped out -- have the highest GI values. Fiber slows digestion and the glycemic effect. Bagels, donuts and pretzels are at the top of the scale of high-GI foods to avoid. Many processed breakfast cereals and white breads have a high glycemic index, over 70.
High GI foods to avoid include starchy foods like French fries, instant mashed potatoes, boiled white potatoes and white rice. The different kinds of carbohydrates -- sugars, starches and fiber -- affect blood sugar differently, and eating carbs with fiber-rich foods slows the glycemic effect.
Most vegetables have a low or medium GI. Very few vegetables such as pumpkins and parsnips have a glycemic index that tops 70. All vegetables have a higher GI value after they ripen. Most vegetables contain fiber that slows their digestion preventing blood sugar spikes. Eating high GI fruits like dates and watermelon in moderation and with fiber-rich foods lowers their glycemic effect.
Sugar- and syrup-sweetened beverages have a high GI. Sugary drinks cause fluctuations of blood sugar levels. In the long term, such fluctuations may result in insulin resistance, a precursor of Type 2 diabetes. Juices made from only ripe fruits and vegetables can also have high GI. Using the pulp from the fruits and vegetables in the juice can lower glycemic index.
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This article reflects the views of the writer and does not necessarily reflect the views of Jillian Michaels or JillianMichaels.com.