An eighteen‐month randomized trial of a low‐glycemic index diet and weight change among Brazilian women

Despite interest in the glycemic index diets as an approach to weight control, few long term evaluations are available. We investigated the long term effect of a low‐glycemic index diet (LGI) compared to a high‐glycemic diet (HGI) ‐ all other dietary components held equal‐ on weight change. After a 6‐week run‐in to assess compliance, we randomized 203 healthy women (body mass index: 23‐30 kg/m 2 ) aged 25‐45 y to low (:n=101) or high (:n=102) glycemic index (GI) diets with a small energy restriction. Despite requiring a run‐in and the use of multiple incentives, only 60% completed the study. Reported energy intake decreased over time, the glycemic index difference between diets approximately 35‐40 units, and carbohydrate intake from energy remained about 60% in both groups. The LGI group had a slightly greater weight loss in the first two‐ month follow‐up (‐0.72 kg vs. −0.31 kg), but after 12 months of follow‐up both groups began to regain weight. After 18 months the weight change was similar (‐0.41 kg vs. ‐0.26 kg; P=0.93). Over time no significant differences were observed between groups for hunger. This study does not support a benefit of a LGI diet for weight loss. Favorable changes in lipids confirmed previous results.