Many popular diets focus on limiting foods and beverages that are high on the glycemic index. Is this really the best approach for healthful and long-term weight control? Read on to learn more!
The glycemic index (GI) for carbohydrate-containing foods and beverages was developed in the early 1980’s with the noble goal of improving blood glucose control in diabetic patients. The GI of a food or beverage is determined by the rise in blood glucose (sugar) levels during the two-hour period following its ingestion versus the blood glucose response to an equivalent amount of carbohydrate in a standard food such as white bread. As a reference point, white bread has a GI of 100. Foods and beverages with a GI higher than 100 (e.g. instant rice) cause a greater rise in blood glucose than white bread, while foods and beverages with a lower GI than 100 cause less of a rise in blood glucose than white bread. For example, if a food has a GI of 33, it would cause only about one-third of the increase in blood glucose as compared to eating an equivalent amount of white bread. Examples of high and low GI foods are shown in Table 1 below. Please note that this Table should not be interpreted as to what to eat or what not to eat!
Table 1. Examples of high and low GI foods and beverages
High GI foods | Low GI Foods |
---|---|
White bread | Beans |
Instant rice | Apples |
Baked potato | Whole grains |
Corn flakes | Apple |
Raisins | Chocolate |
Carrots | Milk |
Watermelon | Bran cereal |
Non-diet soft drinks | French fries |
Pretzels | Full-fat ice cream |
Carrots are classified as a high GI food
Some hip and trendy diets, e.g. South Beach, Atkins, and The Zone strongly recommend the use of the GI to determine what foods should or should not be consumed in order to lose weight and maximize health. Virtually all legitimate nutrition experts (e.g., Registered Dietitians) agree that there are many limitations and flaws to this very narrow type of approach:
For example, a bowl of full-fat ice cream has a low GI, but is loaded with simple sugar, saturated fat and calories, and completely lacking in fiber. On the other end of the spectrum corn, carrots, and raisins have a high GI, but are a great source of fiber, vitamins, minerals, and phytochemicals (non-nutrients found in plant-based foods that have been shown to help prevent disease). For athletes and others who are training for long periods of time on a daily basis, it is extremely important to replace muscle and liver carbohydrate stores (i.e., glycogen) that are depleted each day. Many peer-reviewed studies have shown that consuming high GI foods and beverages during the 30-60 minute period post-exercise actually speeds up muscle and liver carbohydrate replacement, thus speeding up recovery from exercise! So, for highly active individuals, the low GI approach is actually very counterproductive.
Chocolate is classified as a low GI food
Since individuals with diabetes struggle to control their blood glucose level, it might be of interest for you to know what the American Diabetes Association (ADA) has to say about the GI. In their recommendations, they state that individuals with diabetes do not have to limit their food choices to only those that have a low GI. Instead, people with diabetes should focus on the nutrient and fiber content of carbohydrate-containing foods, as well as the amount of carbohydrate consumed. The GI of a food, when considered together with the amount of carbohydrate in the food consumed is known as glycemic load. When it comes to weight loss and good health, individuals are advised to be more concerned with glycemic load as well as nutrient and fiber content, and less concerned with GI.
It is interesting to note that none of the fad diets which strongly promote use of the GI have been shown to be effective for long-term weight control or long-term significant improvements in health, despite claims to the contrary made by their vocal proponents.
As was eloquently stated several years ago by Dr. Xavier Pi-Sunyer, a prominent expert in diabetes, “People and the experts advising them on nutrition can find more worthwhile issues to concentrate on than the glycemic index.” That sums it up quite nicely I think!
Reference
Foster-Powell, K., Miller, J.B. (1995). International tables of glycemic index. Am J Clin Nutr. 62:871S-893S.