July 2007 - Put aside the white bread and pick up an apple. A diet of foods less likely to spike blood sugar levels helps dieters lose more weight, according to a new systematic review from Australia.
"Losing weight is very difficult and many people are unable to sustain a weight-loss diet. The low glycemic index diet is satisfying and has proven benefits," said review co-author Elizabeth Elliott, Ph.D., professor at the University of Sydney, The Children's Hospital at Westmead.
The glycemic index (GI) ranks carbohydrate-rich foods based on their effect on blood sugar levels. Compared to high GI foods such as white rice and French fries, low GI foods, such as lentils, sweet potatoes and apples produce more consistent blood glucose levels. Previous studies have indicated that keeping blood sugar levels steady throughout the day may stimulate more weight loss in obese people.
Researchers evaluated randomized controlled trials that compared weight loss in people eating foods low on the glycemic index to weight loss in people on higher GI diets or other types of weight loss plans.
Six trials, involving 202 adults from Australia, France, South Africa, Denmark and the United States were included in the review. The diets lasted from five weeks to six months.
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The review appears in the latest issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.
The review found that dieters focused on eating low GI foods dropped significantly more weight - about 2.2 pounds more - than participants on other diets. Low GI dieters also experienced greater decreases in body fat measurements and body mass index.
None of the studies reported adverse effects associated with consuming a low glycemic index diet.
"Compared to other diets, the low GI diet is more satisfying - people are less inclined to feel hungry. One advantage of this type of diet is that it is more likely to be maintained than other strict diets on which people feel hungry," Elliott said.
Low glycemic diets appear to be effective even in obese people who need to lose considerable amounts of weight, the authors said.
In the two studies that evaluated only obese participants, low GI dieters lost about 9.2 pounds, compared with about 2.2 pounds shed by other dieters.
Low glycemic index diets might also benefit heart health.
In the three studies that measured cardiovascular risk factors, people eating low GI foods experienced greater improvements in total blood cholesterol and low-density lipoprotein (LDL) - sometimes called "bad" cholesterol. High levels of total cholesterol and LDL cholesterol increase the risks for heart disease.
After reviewing the findings, Lawrence Cheskin, M.D. said, "There's surprisingly little in the way of studies to draw any hard and fast conclusions." Cheskin is director of the Johns Hopkins Weight Management Center and associate professor at Johns Hopkins Bloomberg School of Public Health in Baltimore. He was not involved with the review.
Low glycemic index diets can be effective for weight management, Cheskin said, but the success of low glycemic diets lies with an individual's willingness to comply with its nutritional principles.
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"There aren't many people who need to lose weight who are willing to eat lots of vegetables and whole grains. If they did, they wouldn't have a weight problem in the first place," Cheskin said.
Nevertheless, he said, choosing foods low on the glycemic index does have value for overweight or obese people who want to lose weight.
"It uses a lot of the generally healthful principles, such as eating lots of vegetables and high fiber and avoiding very energy-dense foods that are high in simple sugars and simple carbohydrates," Cheskin said.
Thomas, DE, Elliott EJ, Baur L. Low glycaemic index or low glycaemic load diets for overweight and obesity. (Review). Cochrane Database of Systematic Reviews 2007, Issue 3.