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Weighing the data in studies of the glycaemic index

International Journal of Obesity volume 32, page 1190 (2008)Cite this article

Aston et al.1 recently published a 12-week-crossover study comparing low- vs high-glycaemic-index (GI) diets in 19 overweight and obese women. They report no differences in body weight between diets, or differences in appetite and food intake after representative test meals. The investigators conclude: ‘Claims that the GI of the diet per se may have specific effects on body weight may therefore be misleading.’ However, several important methodological limitations warrant further consideration.

The reported difference in GI between diets of 8.4 U was small, compared not only to the 25 U difference obtained in other clinical trials,2 but also to the range through which GI can vary in the general population (45–70). Of particular significance, glycaemic load (GL) did not differ between groups, owing to an increase in total carbohydrate in the low-GI group. The mechanisms relating GI to body weight are proposed to involve postprandial glycaemia3 and GL is clearly a better predictor of postprandial glycaemia than GI or total carbohydrate.4 Similarly, the glycaemic and insulinaemic response to the test meals were not demonstrated to be different. These observations raise the possibility that both the acute and chronic dietary interventions lack treatment fidelity in that the key physiological exposure, postprandial glycaemia, may not have been sufficiently differentiated between diet groups.

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References

  1. Aston LM, Stokes CS, Jebb SA . No effect of a diet with a reduced glycaemic index on satiety, energy intake and body weight in overweight and obese women. Int J Obes 2007; Online publication, 9 October 2007; doi: 10.1038/sj.ijo.0803717.

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Authors and Affiliations

  1. Division of Endocrinology, Department of Medicine, Children's Hospital Boston, Boston, MA, USA

    D S Ludwig & C B Ebbeling

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  1. D S Ludwig
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  2. C B Ebbeling
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Correspondence to D S Ludwig.

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Ludwig, D., Ebbeling, C. Weighing the data in studies of the glycaemic index. Int J Obes 32, 1190 (2008). https://doi.org/10.1038/sj.ijo.0803785

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