The Glycemic Index (GI) is a measure of the quality of a carbohydrate instead of merely categorizing it as simple or complex. High GI foods are those that are thought to digest quickly and cause a rapid rise in blood sugar (i.e., soda pop, white bread, etc.), whereas low GI foods are digested slowly and cause a slow rise in blood sugar. Therefore, the theory is that high GI foods result in hunger and a tendency to eat more frequently, thus leading to increased calorie intake and obesity.

This theory appears to be confirmed by recent research conducted on 6,334 people between the ages of 30 and 60.  Their diets were analyzed using a food-frequency questionnaire to determine the glycemic index and glycemic load (GL). Both GI and GL and were correlated to individual body mass index (BMI). 

The researchers found both GI and GL to be positively related to BMI – even after adjusting for possible influencing factors such as age, smoking, alcohol intake, physical activity, and calorie intake.  They found that people with high GI diets were significantly more likely to be overweight and concluded that glycemic index may be an important factor for the prevalence of obesity.

What It Means:

Low GI foods have a glycemic index of 55 or less.  In general low GI foods tend to fall into the category of complex carbohydrates (whole grains, vegetables, fruits).  Other low GI foods include soy products, nuts, and legumes.

If you choose foods that have a lower GI, you should feel fuller and be hungry less often; this means you will naturally eat less and help prevent weight gain and obesity.  Eating more low GI foods can help you maintain a healthier weight for a lifetime.

Source:  Lau, C., Toft, L., Tetens, I., Richelsen, B., Jorgensen, T., Borch-Johnsen, K., & Glumer, C. (2006).  Associate between dietary glycemic index, glycemic load, and body mass index.  American Journal of Clinical Nutrition, 84:641-5.