Assessing Low Glycemic Index Diets

by Diane Lofshult on Nov 01, 2006

First, dieters were flocking to high-protein diets like bees to sugar water. This year, savvy consumers are all abuzz about diets with a low glycemic index (GI). (The GI is a numerical system used to rank foods based on how they affect blood sugar levels; low-GI foods are thought to be heart-friendly and able to curb appetite, promoting weight loss.) Despite the popularity of both high-protein and low-GI diets, until this year no randomized, controlled studies had systematically compared these food plans in terms of their relative effects on weight loss and cardiovascular risk.

Now, a new study has done exactly that. Researchers reporting in the July 24 issue of Archives of Internal Medicine assigned a total of 129 overweight or obese young adults to one of four different weight loss plans for 12 weeks. All were reduced-fat, high-fiber diets. Diets 1 and 2 were high in carbohydrate (55% of total energy intake), with high and low GIs, respectively. Diets 3 and 4 were high in protein (25% of total energy intake), also with high and low GIs, respectively.

Although all the subjects lost weight during the program, the proportion who lost 5% or more of their body weight varied significantly by the type of diet: Of those on diet 1 (high carb/high GI), 31% lost 5% or more, compared with 56% of those on diet 2 (high carb/low GI), 66% on diet 3 (high protein/high GI) and 33% on diet 4 (high protein, low GI). Interestingly, women on diets 2 and 3 lost approximately 80% more body fat mass than those on diet 1. Mean LDL cholesterol levels dropped significantly in the diet 2 group but increased in the diet 3 group.

These results led the researchers to conclude that “both high-protein and low-GI regimens increase body fat loss, but cardiovascular risk reduction is optimized by a high-carbohydrate, low-GI diet.”

Fitness Journal, Volume 3, Issue 10

Find the Perfect Job

More jobs, more applicants and more visits than any other fitness industry job board.

© 2006 by IDEA Health & Fitness Inc. All rights reserved. Reproduction without permission is strictly prohibited.

About the Author

Diane Lofshult

Diane Lofshult IDEA Author/Presenter

Diane Lofshult is an award-winning freelance author who specializes in nutrition and weight management topics. She is the founder of In Other Words, an editorial consulting firm based in Solana Beach, California. Reach her at