Low GI diet best for weight loss and cardiovascular health

25 July 2006

The most effective diet for weight loss and cardiovascular health is a high carbohydrate plan based on low glycemic index (GI) foods, according to a study by University of Sydney researchers.

Published in the most recent issue of Archives of Internal Medicine, the world's first 12 week parallelled, randomised, controlled trial compared the relative effects on weight loss and cardiovascular risk of low GI and high-protein diets.

Undertaken by Professor Jennie Brand-Miller and Joanna McMillan-Price from the University of Sydney Human Nutrition Unit, the findings show that there is no 'one diet fits all' solution, and although both high protein and low GI diets will help you to shed fat. However, it did show that a diet containing low GI carbohydrate significantly reduces your risk of heart disease.

The trial, which was led by Joanna McMillan-Price, enrolled 129 overweight or obese young adults (aged 18-40 years) and randomly assigned them to one of four reduced calorie, reduced fat diets over a 12 week period. Two of the diets were high-carbohydrate diets and the other two high in protein - one of each had a high GI and the other had a low GI.

Between the two high-carbohydrate diets, lowering the glycemic index doubled fat loss - this effect was strongest in women. Participants on the high-protein, high GI diet was equally effective for fat loss as the high carbohydrate, low GI diet, the two had diverse effects on LDL (bad) cholesterol - the high protein, high-GI group showed increased levels of LDL or 'bad' cholesterol, while there were significant reductions in those on the high carbohydrate, low-GI diet. However those on the high-protein, low GI diet did not experience the same rise in total LDL cholesterol suggesting the importance of low GI foods alongside a high meat intake.

'Our findings suggest that dietary glycemic load, and not just overall energy intake influences weight loss and postprandial glycaemia (blood sugar levels after eating),' said Joanna McMillan-Price.

'We found that moderate reductions in glycemic load appear to increase the rate of body fat loss, particularly in women. Diets based on low-glycemic index, whole grain products, tend to be better for the heart, maximising cardiovascular risk reduction - particularly if protein intake is high,' said Joanna McMillan-Price.

Notes to Editors:

  • The theory behind low-glycemic index diets is that rapidly digested, high-glycemic index carbohydrates cause fluctuations in blood glucose (sugar) and insulin levels, contributing to hunger and preventing the breakdown of fat.

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