Endocrine Abstracts

Whether high glycaemic index/glycaemic load (GI/GL) diets increase low-grade inflammation leading to changes in body composition and risk for chronic illness remains uncertain. We recently completed a randomised, double-blind study comparing the effects of a 45 g whey protein supplement (PRO) and an isocaloric maltodextrin supplement (CHO) on bone density and body composition in older adults. The study afforded an opportunity to evaluate the impact of a calibrated increase in GI/GL on markers of inflammation, insulin resistance and body composition. Eighty-four postmenopausal women who consumed a minimum of 20 g of either supplement (PRO, n=38; CHO, n=46) daily for 18 months were studied. GI/GL was estimated from 3-day food records at baseline and 18 months. At the end of 18 months the GL in the CHO group increased by 34%, 88.4±5.2 to 118.5±4.9 (P<0.0001 at 18 months) and did not change in the PRO group 86.49±4.14 to 81.9±3.6. Despite this, there were no differences in serum CRP, IL-6, or HOMA at 18 months between the two groups, nor when the individuals in the highest quartile (n=21) of GL at 18 months were compared to the lowest quartile (n=20). However, analysis of body composition showed a significant increase in truncal lean mass (P=0.007) and total lean mass (P=0.038) in the PRO group, compared to the CHO group. In contrast, the highest GL quartile had significantly higher BMI (P=0.03) and total fat mass (P=0.005) with a significant decline in the lean/fat ratio (P=0.0008). Our data suggest that as dietary GL increases within the moderate range, there is no detectable change in markers of inflammation or insulin resistance, despite which there is a negative effect on lean body mass.