Sydney, Australia - A new Cochrane review of six randomized controlled trials comparing low-glycemic-index (GI) or glycemic-load (GL) diets with other diets has found that overweight or obese people lost more weight and had more improvement in lipid profiles with the low-GI eating plans [1]. Dr Diana E Thomas (Children's Hospital at Westmead, Sydney, Australia) and colleagues publish their findings online July 18, 2007 in the Cochrane Database of Systematic Reviews.

Those on the low-GI diets lost an average of 2.2 pounds (1 kg) more than those given comparison diets, which included higher-GI or -GL diets and conventional weight-loss diets. They also had significantly better decreases in total and LDL cholesterol, the researchers note. And in the two trials that evaluated only obese participants, weight loss was even more apparent—the low-GI dieters lost about 9.2 pounds, compared with about 2.2 pounds shed by those on the other diets.

However, the scientists caution that enduring data are still needed. "Longer trials with increased length of follow-up will determine whether the improvements reported can be maintained and incorporated into lifestyle long term," they say.

Two experts not connected with the review expressed mixed opinions. One said this was a great review, while the other pointed out that the difference in weight loss between the low- and high-GI diets was rather small.

Thomas and colleagues included six trials in their review, including a total of 202 adults from Australia, France, South Africa, Denmark, and the United States. The diets lasted from five weeks to six months, and none of the studies reported any adverse effects associated with consuming a low-GI diet.


As well as losing more weight, those on the low-GI diets also had significantly greater loss of total fat mass and decrease in body-mass index (BMI) than those on the comparison diets. "The loss of 1 to 2 BMI units is clinically significant, as is the weight loss observed with low-GI diets," Thomas et al note. "Considering the brevity of the interventions, the results are notable," they add.

Improvements in blood lipids were also significant—those on the low-GI diets saw a mean drop of 0.22 mmol/L in total cholesterol and 0.24 mmol/L in LDL cholesterol (both p<0.05).

"Our systematic review may clarify issues surrounding the role of low-GI or -GL diets in the management of obesity and overweight," the researchers note.

They add that the degree of overweight and obesity in the populations included in these studies "was wide, suggesting that the results would be applicable in other developed communities." However, they caution that only one trial included children (n=16), "so care would need to be taken in generalizing results in the pediatric population."

It strikes me that the difference in weight loss between low- and high-GI diets is . . . of a rather tiny magnitude.

Dr Simin Liu (director of the program on genomics and nutrition, David Geffen School of Medicine, University of California, Los Angeles) told heartwire: "This looks like an excellent and fairly comprehensive work, which essentially confirms what we have seen in our epidemiologic work."

But another expert is not that impressed by the findings. Dr Lawrence Cheskin (director, Johns Hopkins Weight Management Center, Baltimore, MD) commented to heartwire: "It strikes me that the difference in weight loss between low- and high-GI diets is, while statistically significant, of a rather tiny magnitude."