The Glycemic Index Diet (Low-Glycemic Diet)
Some studies have shown weight management and disease prevention benefits from using the glycemic index.
"Using the GI to improve carb quality can improve overall healthfulness of diets, promote weight loss, weight maintenance, and reduce the risk of chronic diseases," Ludwig says.
In 2010, a study published in the New England Journal of Medicine found the GI, in combination with higher protein, helped overweight adults in eight European countries maintain their weight. However, the 2010 Dietary Guidelines for Americans states that "consistent evidence shows that glycemic index and/or glycemic load are not associated with body weight and do not lead to greater weight loss or better weight maintenance.
A 2008 report, which analyzed data from 37 studies and was published in the American Journal of Clinical Nutrition, linked low-GI diets to lower risk of heart disease, diabetes, and some cancers. However, that does not prove that the low-GI diets prevented those diseases.
Glycemic Index Controversy
The GI is not a perfect tool and is no guarantee of healthy fare. Brown and white rice rank comparably on the index scale as do white and whole wheat bread, yet clearly the whole grain choices are healthier.
Some scores are confusing. For example, carrots are a nutrient-rich, high-fiber vegetable that can range from low to high on the GI scale. Likewise, some candy that includes nuts gets a better GI score than a potato. Ripe bananas have higher GI scores than under-ripe bananas. Cook pasta al dente and it ranks lower than fully cooked pasta.
Not only do the food scores vary, but so does the response from person to person. It can even vary within the same person from day to day, according to research reported in the June 2007 issue of Diabetes Care.
Furthermore, no one eats a single food in isolation. When carbs are paired with other foods, it impacts how blood sugars are affected -- that's the glycemic load, which ranks foods based on carbs and portion size.
Some nutrition experts don’t put much stock in the GI as an effective weight loss tool because of all the variability associated with the numbers.
"Using the GI to lose weight is unnecessarily complicated, and it does not simplify the task of choosing healthier food to lose weight or manage blood sugar," says Hope Warshaw, MMSc, RD, a certified diabetes educator and author of books about diabetes including Diabetes Meal Planning Made Easy.
Some experts see the glycemic index as just another gimmick because there is little evidence that an elevated blood sugar level leads to weight gain if you are healthy.
How to Choose Healthier Carbs
"Look at the bigger picture. Use the GI scale to choose quality carbs that are healthy, natural, whole, and in the least processed state," Ludwig says.