McMillan-Price J et al. (2006) Comparison of 4 diets of varying glycemic load on weight loss and cardiovascular risk reduction in overweight and obese young adults: a randomized controlled trial. Arch Intern Med 166: 1466–1475

With the recent surge in popularity of low-carbohydrate and low-glycemic-index (GI) diets, the traditionally recommended low-fat, high-carbohydrate weight-loss diet has lost favor. A 12-week, randomized, controlled Australian study has compared the effects of four types of diet on weight loss and cholesterol level.

A group of 129 overweight volunteers was stratified by weight and sex. Participants were allocated to one of four low-fat diet groups: high carbohydrate, high GI (Group 1); high carbohydrate, low GI (Group 2); high protein, high GI (Group 3); or high protein, low GI (Group 4).

The mean percentage of body weight lost was similar for all groups (4.2–6.2%), but the proportion of patients who lost >5% of their body weight was higher in Groups 2 and 3 than in Groups 1 and 4 (56% and 66% versus 31% and 33%, respectively). Women in Groups 2 and 3 lost almost twice as much fat mass compared with women in Group 1 (approximately 4.5 kg versus 2.5 kg, respectively). LDL cholesterol levels, however, significantly increased in Group 3, and declined in Group 2.

These results suggest that the traditional diet (Group 1) is not the best option for weight control. Although the high-protein, high-GI diet resulted in the greatest loss of fat mass, it also increased participants' LDL cholesterol levels. This study suggests that the best results, in terms of both weight loss and reduction of cardiovascular risk, are obtained by following a high-carbohydrate and low-GI diet—especially for women.