Effectiveness Of Low Glycaemic Index Diets In The Management Of Glucose Homeostasis, Cardio-Vascular Risks And Body Weight Among Women With A History Of Gestational Diabetes Mellitus: A Randomised Controlled Trial

Abstract

Background: Women with previous Gestational Diabetes Mellitus (GDM) have increased risk for type 2 diabetes mellitus. Conventional diets for risk prevention have limited success in achieving or sustaining weight loss in them. Lowering dietary glycaemic index (GI) has been shown to facilitate greater weight loss in subjects with insulin resistance. Hence, we evaluated the effects of adding low GI nutrition education to conventional healthy dietary recommendations on glucose homeostasis, cardiovascular risks and body weight of women with previous GDM. Methodology: Seventy seven, non-diabetic, women with previous GDM (aged 20-40y, mean BMI: 26.4±4.6kg/m2) were randomised into two groups. Thirty-eight subjects received only conventional dietary recommendations (CHDR). Thirty-nine subjects received in addition to CHDR, low GI education (LGI). Changes in fasting (FBG) and 2h-postprandial blood glucose (2HPP), fasting insulin, blood pressure, fasting serum lipids, high sensitivity C-reactive protein, endothelial dysfunction, anthropometric measures, body composition and dietary intakes were measured before and after intervention. Results: After 12 months of intervention, CHDR subjects had significant increase in FBG, total body fat (both p<0.01) and trunk fat (p<0.05). CHDR subjects also had significant reductions in LDL Cholesterol (p<0.001). WHR significantly reduced in LGI group (p<0.05). Subjects in both groups had significant reductions in lean body mass (p<0.001), total: HDL Cholesterol and LDL: HDL Cholesterol ratios (p<0.05). However, changes in none of the outcomes measured were statistically different between groups (p≥0.05). Nevertheless, the magnitude of FBG increase was two-fold higher in the CHDR group (0.2±0.3 vs.0.3±1.0mmol/L, p=0.967, ES 0.6 vs. 0.3). Similarly, the magnitude of total body fat increase was also higher in the CHDR group, compared with the LGI group (1.2±2.4 vs. 0.87±2.7kg, p=0.580, ES 0.5 vs. 0.3). After 12 months, LGI group had a mean weight loss four times in magnitude to that observed in CHDR group (mean ± SD): 1.03±4.1 and 0.16±2.8kg, p=0.280, effect size 0.25 vs. 0.06). More subjects in LGI group attained 7% (p<0.01) and 10% (p<0.05) weight loss. After intervention, calculated dietary GI of LGI subjects were significantly lower (58 vs.64, p<0.001). Estimated intakes of dietary fibre was also significantly higher among LGI compared to CHDR subjects (17 vs. 13g, p<0.001). Interestingly, sub-group analysis showed LGI intervention had favourable outcomes in terms of managing FBG and triglycerides especially among subjects with higher baseline fasting insulin levels (p<0.05). Conclusion: LGI and CHDR nutrition-education interventions were comparable in terms of managing glucose homeostasis, cardiovascular risks and body weight among women with previous GDM one year after intervention. However, more subjects in LGI group achieved a clinically significant weight loss. Also, LGI nutrition education improved dietary fibre intakes as compared to CHDR. Low GI diets are a viable alternative to iso-caloric low-fat diets in managing post-GDM metabolic risks.