Low-GI and/or low-GL diets are independently associated with a reduced risk of certain chronic diseases. In diabetes and heart disease, the protection is comparable with that seen for whole grain and high fiber intakes. The findings support the hypothesis that higher postprandial glycemia is a universal mechanism for disease progression.

Both high-protein and low-GI regimens increase body fat loss, but cardiovascular risk reduction is optimized by a high-carbohydrate, low-GI diet.

Weight loss can be achieved by any means of energy restriction, but the challenge is to achieve sustainable weight loss and prevent weight "creep" without increasing the risk of chronic disease. The modest success of low fat diets has prompted research on alternative dietary strategies, including high protein diets and low glycemic index (GI) diets. Conventional high carbohydrate diets, even when based on wholegrain foods, increase postprandial glycemia and insulinemia and may compromise weight control via mechanisms related to appetite stimulation, fuel partitioning, and metabolic rate. This paper makes the case for the benefits of low glycemic index diets over higher protein diets. Both strategies are associated with lower postprandial glycemia, and both are commonly labeled as "low glycemic load," but the long-term health effects are likely to be different. A large body of evidence, which now comprises observational prospective cohort studies, randomized controlled trials, and mechanistic experiments in animal models, provides robust support for low GI carbohydrate diets in the prevention of obesity, diabetes, and cardiovascular disease. Although lower carbohydrate, higher protein diets increase the rate of weight loss, cohort studies and meta-analyses of clinical trials suggest the potential for increased mortality.

Low-fat diets produce spontaneous weight loss in the research setting, but as a public health strategy, they have been disappointing. Insulin resistance and impairments in insulin secretory function leading to postprandial hyperglycaemia are now common, making the current context greatly different to that of 25 years ago. There is increasing evidence that reducing the proportion of energy derived from carbohydrate or reducing the glycaemic index (GI) of the carbohydrate improves the rate of fat loss and cardiovascular risk factors. The proposed mechanisms include higher satiety, higher metabolic rate, reduced postprandial glycaemia and/or insulinaemia and higher fat oxidation. Although dietary glycaemic load can be reduced either by lowering the GI of the carbohydrate or by reducing carbohydrate energy, the metabolic and physiological consequences are not the same. Exchanging high for low-GI foods, without changing the macronutrient ratio, may be optimal because it is simple, cost-effective and often associated with higher intake of whole grains and greater food volume, and factors that maximize the chance of sustained weight loss. Healthy low-GI diets allow for moderate intakes of sugars, including sweetened dairy foods, fruits and confectionery items, and can be easily adapted for individuals of different ethnicities, vegetarians and low-income groups.

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