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-week. All four diets 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 glycemic index and high protein diets on weight loss and cardiovascular risk.
The diets varied in target levels of carbohydrates, proteins, and glycemic load (i.e., glycemic index multiplied by the amount of carbohydrate, divided by 100) as follows:
Diet 1: carbohydrates comprise 55 percent of total energy intake, protein 15 percent of total energy intake, and high glycemic load (127 g)
Diet 2: similar to diet 1 except with a lower glycemic load (75g)
Diet 3: protein comprises 25 percent of total energy intake (based on lean red meat), carbohydrates reduced to 45 percent of total energy of intake, and high glycemic load (87 g)
Diet 4: Similar to diet 3, except with a low glycemic load (54 g).
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 high-carbohydrate diets, lowering the glycemic load doubled the fat loss. The investigators also found that total and LDL (“bad”) cholesterol levels increased with diet 3 and decreased in diet2.
In the short term, findings suggest that dietary glycemic load, and not just overall energy intake, influences weight loss, Foods with a low degree of starch gelatinization, such as pasta, and those
containing a high level of viscous soluble fiber, such as wholegrain barley, oats, and rye, have slower rates of digestion and lower glycemic index values.
Without any drastic change in regular dietary habits, one can simply replace high glycemic index grains with low glycemic index grains and starchy vegetables with less starchy ones and cut down on soft drinks, that are often poor in nutrients yet high in glycemic load.