Sydney: New research has shown that a diet which scores low on the “glycaemic index” (GI) helps overweight people lose body fat and reduce their levels of “bad” cholesterol, which contributes to the risk of heart attacks and strokes.

A study of 189 overweight and obese adults, carried out by the University of Sydney concluded that a diet high in either protein or carbohydrates, but with a low total GI score, brought about the biggest reduction of body fat, and that a high-carbohydrate and low GI diet caused the greatest drop.

The researchers studied men and women aged 18-40 assigned to one of four reduced-calorie and reduced-fat diets for 12 weeks.

The first diet was high in carbohydrates (55 percent of total energy) but low on the GI index. The second was high in carbohydrates and high in GI rating. The third was high in protein(25 percent of total energy) and high in GI score, while the fourth was also high in protein but low in GI score.

After three months, all the volunteers lost a statistically similar amount of weight: between 4.2 and 6.2 percent of their body weight. However, those on the low GI diets lost the most body fat, with those on the high-carb, low-GI diet losing about 80 percent more body fat than those on the high-carb and high-GI diet.

As for cholesterol levels, the researchers said the effects of each diet varied, with those eating the high-protein, high-GI diet seeing their LDL cholesterol level increase, while those on the high-protein, low GI regimen, saw cholesterol levels go down slightly.

The GI measures the impact of carbohydrates on blood sugar levels. Food with a high GI score, like biscuits, causes sharper peaks in sugar levels than low GI food, such as pasta, which makes people feel fuller for longer, and may promote the breakdown of fat and reduce total and low density lipoprotein (LDL), or “bad” cholesterol.