A new paradigm is arising in nutrition: the processed carbohydrates which have replaced the energy from fat may increase the risk of obesity, diabetes and cardiovascular disease more so than fat or saturated fat. Both quantity and quality of carbohydrate are relevant. Sugars and starches, with or without fibre, can increase postprandial glycaemia, a characteristic that reflects their rate of digestion and absorption, and is assessed as their glycaemic index or glycaemic load per serving.
Meta-analyses indicate that low GI diets reduce glycated hemoglobin by an average of 0.4-0.6% points over and above that achieved by with conventional healthy diets1. Large multicentre international studies such as DIOGENES2 have also demonstrated the combination of moderately high protein and low GI carbohydrates improves weight loss, weight maintenance, insulin sensitivity, serum lipids and inflammatory markers on low GI vs conventional low fat diets. Alternate dietary approaches, including Mediterranean-style diets, have also been shown to improve glycaemia, weight control and cardiovascular outcomes more so than conventional low-fat, high-carbohydrate diets.
These alternate diets share an under-recognised unifying mechanism: the reduction of postprandial glycaemia and insulinaemia. While intake of saturated and trans fat should remain low, a singular focus on reduction on fat is counterproductive. Alternate healthy diets offer greater flexibility and are more sustainable over the longer term. Most diabetes organisations around the world now recommend the judicious use of the GI, application to other areas such as weight control and heart disease is still debated.