A diet high in certain carbohydrates may help people who are overweight to lose body fat and reduce their risk of heart attack and stroke, a diet comparison shows.

Researchers directly compared high protein diets to those low on the glycemic index, which measures the impact of carbohydrates on blood sugar levels.

Whole grains are a better option to encourage weight loss.
(CBC)

A high-carbohydrate, low GI diet caused the greatest drop in total and low density lipoprotein or LDL "bad" cholesterol levels, the team reports in this week's issue of the Archives of Internal Medicine.

"In terms of weight and fat loss [a low GI diet] and [a high protein diet] were exactly the same," said lead author Joanna McMillan-Price from the University of Sydney's human nutrition unit and co-author of a book on low GI diets.

"There was no difference in terms of weight or fat loss between those two studies."

The theory is that highly processed, rapidly digested carbohydrates that are high on the glycemic index such as mashed potatoes or cookies cause fluctuations in blood sugar and insulin levels that contribute to hunger and prevent the breakdown of fat.

McMillan-Price and her colleagues recruited 129 obese or overweight men and women aged 18 to 40 who were randomly assigned to one of four reduced calorie, reduced fat diets for 12 weeks.

The diet with high GI foods showed the slowest rate of weight loss, while those on a high protein diet showed increases in LDL cholesterol, the team reports.

Replacing grains

Both high protein and low GI diets can reduce weight, said Peter Clifton, research director of human nutrition at the Australian Commonwealth Scientific and Research Organization.

"Certainly [the study] doesn't provide any evidence [low GI diets] are the best; they're an equivalent," said Clifton, who co-authored a book on high protein diets, which he says are more likely to leave you feeling fuller for longer.

Given the findings of this and other studies, doctors should introduce the concept of the glycemic index when making diet recommendations for patients, said Dr. Simin Liu of the University of California, Los Angeles in an accompanying editorial.

"Typically, foods with a low degree of starch gelatinization, such as pasta, and those containing a high level of viscous soluble fiber, such as whole grain barley, oats and rye, have slower rates of digestion and lower glycemic index values," Liu wrote.

"Without any drastic change in regular dietary habits, for example, one can simply replace high–glycemic index grains with low–glycemic index grains and starchy vegetables with less starchy ones and cut down on soft drinks that are often poor in nutrients yet high in glycemic load." 

McMillan-Price's study received funding from Meat and Livestock Australia.

With files from Australian Broadcasting Corp.