Impact of dietary glycaemic index on metabolic disease risk

• Main Author: Aston, L. M.
• Published: University of Cambridge 2006
• Subjects: 612.3
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596202

An initial study determined the GI values of a number of key ‘staple’ carbohydrate-rich foods (chapter 2). This allowed consideration of some of the factors which influence the GI of foods, and also identified low and high FI versions of these staple foods for use in a controlled dietary intervention study. This intervention study investigated the effects of <i>ad libitum</i> low and high GI diets in overweight, hyperinsulinaemic female subjects (chapter 4). It also explored some of the potential mechanism for any effects on metabolic disease risk. The study employed a novel method for the assessment of insulin sensitivity, and the acceptability and suitability of this for use in intervention studies was examined (chapter 3). Data from the cohort of subjects reported here indicate beneficial effects of a reduction in dietary GI by 8 units on insulin sensitivity and secretion. An improvement was also seen in circulating IL-6 levels, as a marker of inflammatory status, and it is possible that this could, at least in part, have mediated the effect on insulin sensitivity. There was no improvement in a range of other markers of cardiovascular disease risk, no effects on appetite or energy intake, either in the short or long-term, and no effects on body weight. Neither was any difference seen in 24-hour glucose profiles between the diets. This calls into question these putative mechanisms for beneficial effects of low GI diets. In conclusion, the work described here is largely consistent with the wider literature in suggesting a beneficial effect of low GI diets on metabolic disease risk, although effects appear to be subtle, which may explain the inconsistencies in the literature. Longer, better-controlled studies with precise outcome measures are still needed.