Amy Fleishman, a registered dietician at Mt. Sinai Medical Center, says, “The thought is out there that the lower the glycemic index, the lower the uptake of glucose in your body. All of this more or high is compared to a standard, a piece of white bread.” The study compared four reduced-calorie, reduced-fat diets for a 12-week period. Two were high-carbohydrate diets and two were high-protein diets; one of each had a high glycemic load and the others had low glycemic loads.
At the end of the 12 week period, the participants in all four studies lost essentially the same amount of weight. But the authors say those on the low glycemic index diet doubled the fat loss compared to those on the high glycemic index diet. Participants on the high-protein, high-glycemic index diet had increased levels of total and LDL or bad cholesterol, while those on the high-protein, low-glycemic index diet and high carbohydrate, low-glycemic index diet experienced reductions in total and LDL cholesterol.
“Some people think, although it hasn’t been proven, that it can affect weight changes, appetite, people who are diabetic,” says Ms. Fleishman. In fact, the American Dietetic Association said in October of last year that “research does not support the claim that a low glycemic index diet causes significant weight loss or helps control appetite.”
Well, maybe this study shows it might; but that doesn’t make it an easy diet to follow at all! “There’s nothing on a label that will tell you what a glycemic index is. You can have a potato that has a high glycemic index and a candy that has a low glycemic index,” states Ms. Fleishmn. And, the study was also not perfect.
The group on the low glycemic index diet also had the lowest fat content, and was higher in fiber, which would skew the results in its favor. And the study was only 12 weeks, it was not a long term look at the benefits of the diet. There are some basics that are true: for example, on the whole fruits are low glycemic index. But even that’s fraught with problems.
“Glycemic index is affected by the ripeness of the fruit, the variety, by how you cook it by how you process it. It’s also affected from person to person. I still don’t believe that glycemic index is the way to go on terms of weight loss counseling,” argues Ms. Fleishman. So the jury is still out.