Effect of including Glycaemic Index (GI) nutrition education, within the conventional healthy dietary recommendation framework, on body weight and composition of women with prior Gestational Diabetes Mellitus: results from a one-year randomised Controlled Trial

Introduction : Women with previous gestational diabetes mellitus (GDM) have increased risks for obesity and its metabolic consequences. Conventional diets have limited success in achieving weight loss in this population. Lowering dietary glycaemic index (GI) is known to facilitate weight loss in insulin-resistant women. This study evaluated the effects of including GI education within the conventional healthy dietary recommendation (CHDR) framework, on body weight and composition of women post-GDM. Methods : Seventy-seven, non-diabetic, women with previous GDM (aged 20-40y, mean BMI: 26.4±4.6kg/m²) were randomised into two groups: subjects who received CHDR only (CHDR, n=38) and those who received low-GI education in addition (LGI, n= 39). The outcome of these interventions on body weight, waist circumference (WC), waist¬to-hip-ratio (WHR), body fat and dietary intakes were assessed after one year. Clinically significant weight loss was defined as achieving a minimum of 5% weight loss from the baseline body weight. Results : After one year, as compared to CHDR, a significantly greater proportion of LGI subjects had 7% (28.2% vs. 5.3%, p =0.01) and 10% (15.4% vs. 0%, p =0.025) weight loss from baseline. WC significantly reduced in both groups (p< 0.004); however, only LGI subjects had significant WHR reduction (-0.02± 0.04, p=0.035). One-year mean increases in total (1.2±2.4kg, p= 0.008) and trunk fat (0.65±1.4kg, p= 0.019) were significant only within the CHDR group, although the changes were not significantly different between the groups. After intervention, LGI as compared to CHDR diets, had lower GI (58±4 vs.64±7, p<0.001) and higher dietary fibre (17±4 vs. 13±4g, p <0.001). Conclusion : Including GI education within the CHDR framework for women with prior GDM, increases their likelihood of achieving ≥7% weight loss and significant WHR reductions in one year.