The Truth About Low-Glycemic Diets

Lawrence Appel, M.D., M.P.H.

It is the season to be considering diet strategies — in fact, over 20 percent of Americans’ New Year’s resolutions are about weight loss. But if your plan is to adopt a low glycemic diet to achieve your goal, you may want to think twice.

While proponents insist the diet helps with shedding extra pounds and maintaining a healthy weight, Johns Hopkins researcher Lawrence Appel says the evidence doesn’t support these claims. "Glycemic index has conceptual appeal, but evidence is inconsistent and there are a lot of technical issues that make it problematic," says Appel, director of the Welch Center for Prevention, Epidemiology and Clinical Research.

The Lowdown on Low Glycemic Diets
Enticed by the promise of being able to enjoy carbohydrates at every meal, devotees have created a lot of buzz around low glycemic diets. Unlike their no-carb counterparts, low glycemic eating plans do not restrict carbohydrate intake altogether.

Instead, followers abide by the glycemic index (GI), a ranking system that assigns a number from 0 to 100 to carbohydrates based on their effect on blood sugar levels. Foods with a number of 55 or lower, such as broccoli and apples, are considered low GI foods, and adherents of the diet can eat these at every meal. Medium GI carbs, such as rye bread and raisin bran cereal, score 56 to 69 and should be eaten less frequently.

Dieters should avoid high GI carbs, such as instant oatmeal and mashed potatoes, which rank 70 or above on the index.

Good Carbs Versus Bad Carbs
Appel recently co-chaired a study published in the Journal of the American Medical Association that found strong evidence indicating that the glycemic ranking of carbohydrates does not affect insulin sensitivity, cholesterol levels, or blood pressure. He says the nomenclature associated with the diet itself is problematic.

"We need to figure out a better way to classify carbohydrates. We don’t have the perfect system for good and bad carbs, but we should cut down on foods high in sugar, like sugar-sweetened beverages," he says.

So what are the keys to losing weight and promoting heart health in the New Year?

Cut down on salt and sugar.
Stick to a heart-healthy diet of fruits, vegetables and whole grains.
Follow Appel's advice: "Eat less. Eat right. Move more."