The Effect of Dietary Glycemic Properties on Markers of Inflammation, Insulin Resistance and Body Composition in Postmenopausal Women

Abstract

Whether high glycemic index/glycemic 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 study comparing the effects of a 45 g whey protein supplement (PRO) and an isocaloric maltodextrin supplement (CHO) on BMD 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 the end of 18 months the GL in the CHO group increased by 34%, 88.4±5.2 → 118.5±4.9 (P<0.0001) and did not change in the PRO group, 86.5±4.1 → 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 individuals in the highest GL quartile (N=21) were compared to the lowest quartile (N=20). At 18 months, truncal lean mass (P=0.007) and total lean mass (P=0.04) were significantly higher 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.