Why Low Glycaemic Index Diets are better than High Protein Diets
An Australian research team led by Dr. Jennie Brand-Miller at the University of Sydney conducted a trial in which 129 overweight subjects ages 18 to 40 were randomly assigned to one of four weight-loss diets for 12-weeks. All four diets were based on reduced fat (30 percent of total energy intake) and held daily calories to 1400 kcal for women and 1900 kcal for men.
This was the first clinical trial comparing the effects of glycaemic index and high-protein diets on weight loss and cardiovascular risk.
The diets varied in target levels of carbohydrates, proteins, and glycaemic load (i.e., glycaemic index multiplied by the amount of carbohydrate, divided by 100) as follows:
Diet 1: carbohydrates comprises 55 percent of total energy intake, protein 15 percent of total energy intake, high glycaemic load (127g)
Diet 2: similar to Diet 1 except a lower glycaemic load (75g)
Diet 3: protein comprises 25 percent total energy intake (based on lean red meat), carbohydrate reduced to 45 percent total energy of intake, and high glycaemic load (87g)
Diet 4: Similar to Diet 3, except low glycaemic load (54g)
Brand-Miller and her team report that the diets resulted in similar reductions in weight (4.2 percent to 6.2 percent of body weight), fat mass and waist circumference.
However, in the high-carbohydrate diets, lowering the glycaemic load doubled the fat loss. The investigators also found that total and LDL ("bad") cholesterol levels increased with Diet 3 and decreased in Diet 2.
In the short term, findings suggest that dietary glycaemic load, and not just overall energy intake, influences weight loss.
Foods with a low degree of starch gelatinisation, such as pasta, and those containing a high level of viscous soluble fibre, such as wholegrain barley, oats, and rye, have slower rates of digestion and lower glycaemic index values.
Without any drastic change in regular dietary habits, one can simply replace high glycaemic index grains with low glycaemic index grains and starchy vegetables with less starchy ones and cut down on soft drinks, that are often poor in nutrients yet high in glycaemic load.
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