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LETTERS TO THE EDITOR |
Nutrition and Food Science Group
School of Biological and Molecular Sciences
Oxford Brookes University
Headington Campus
Gipsy Lane
Oxford OX3 0BP
United Kingdom
E-mail: cstrik{at}brookes.ac.uk
Dear Sir:
In a recent issue of the Journal, Sloth et al (1) describe the results of an interesting and well-designed study that compared the effects of a high-glycemic-index diet with those of a low-glycemic-index (GI) diet on weight loss. We wish to raise some issues that may help further clarify the important contribution of these researchers. One of the primary mechanisms by which low-GI foods may facilitate weight loss is via their ability to enhance satiety and reduce subsequent food intake (2, 3). In the study by Sloth et al, 2 matched groups were assigned to ad libitum intake of diets rich in either high- or low-GI foods. However, to achieve a high- or low-GI diet, the subjects were required to consume a defined amount of test carbohydrate (
48% of their total energy intake) assigned by the researchers. Sloth et al commented in their article that many of the subjects had difficulty consuming the large amount of test foods. Consequently, we wondered whether feeding such a large amount of test carbohydrate, which is bulky to consume, may have limited the voluntary ad libitum food intake of the subjects and masked any potential influence of GI on energy intake.
Second, the authors concluded that there were no significant differences in body weight or, more notably, in percentage body fat changes between the groups over the test period. However, the trend (although nonsignificant) for greater weight loss and reduction in percentage body fat was more apparent in the subjects fed the low-GI diet. Indeed, it is generally recognized that reductions in percentage body fat are clinically more important than are reductions in body weight per se. The mean difference in energy intake between the groups (low-GI group: 9.0 ± 0.2 MJ/d; high-GI group: 9.6 ± 0.3 MJ/d) was 0.6 MJ (143 kcal)/d. This difference in energy intake, although not statistically significant, may be of physiologic importance and lead to weight loss over a prolonged period (4).
Finally, we believe that the title of Sloth et al's article, "No difference in body weight decrease between a low-glycemic-index and a high-glycemic-index diet but reduced LDL cholesterol after a 10-wk ad libitum intake of the low glycemic-index diet," may be misleading. Our concern is that the authors' conclusions may discourage others from researching the potential role of low-GI diets in the management of obesity.
ACKNOWLEDGMENTS
We received a research grant from the Sugar Bureau, and our research group has done glycemic index testing for Tesco and the British Potato Council.
REFERENCES
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