Differential Glycemic Effects of Low- versus High-Glycemic Index Mediterranean-Style Eating Patterns in Adults at Risk for Type 2 Diabetes: The MEDGI-Carb Randomized Controlled Trial

Abstract

A Mediterranean-style healthy eating pattern (MED-HEP) supports metabolic health, but the utility of including low-glycemic index (GI) foods to minimize postprandial glucose excursions remain unclear. Therefore, we investigated the relative contribution of GI towards improvements in postprandial glycemia and glycemic variability after adopting a MED-HEP. We conducted a randomized, controlled dietary intervention, comparing high- versus low-GI diets in a multi-national (Italy, Sweden, and the United States) sample of adults at risk for type 2 diabetes. For 12 weeks, participants consumed either a low-GI or high-GI MED-HEP. We assessed postprandial plasma glucose and insulin responses to high- or low-GI meals, and daily glycemic variability via continuous glucose monitoring at baseline and post-intervention. One hundred sixty adults (86 females, 74 males; aged 55 ± 11 y, BMI 31 ± 3 kg/m2, mean ± SD) with ≥two metabolic syndrome traits completed the intervention. Postprandial insulin concentrations were greater after the high-GI versus the low-GI test meals at baseline (p = 0.004), but not post-intervention (p = 0.17). Postprandial glucose after the high-GI test meal increased post-intervention, being significantly higher than that after the low-GI test meal (35%, p < 0.001). Average daily glucose concentrations decreased in both groups post-intervention. Indices of 24-h glycemic variability were reduced in the low-GI group as compared to baseline and the high-GI intervention group. These findings suggest that low-GI foods may be an important feature within a MED-HEP.

Replacing Foods with a High-Glycemic Index and High in Saturated Fat by Alternatives with a Low Glycemic Index and Low Saturated Fat Reduces Hepatic Fat, Even in Isocaloric and Macronutrient Matched Conditions

“…Glycemic variability, measured as the coefficient of variation (%CV), over four weekdays was significantly lower during the low-GI/SFA diet when compared to the high-GI/SFA diet. This finding is in line with previous studies showing that a higher-glycemic-index diet significantly increased glycemic variability [ 34 , 35 ]. Monitoring glycemic variability was also a good way to check participants’ adherence to the diet, and our findings confirm that participants indeed adhered to the high-GI or low-GI diets.…”

“…This was especially apparent after lunch ( p < 0.05; Figure 2 C). This is in line with findings from Bergia et al [ 34 ] who reported seeing more robust differences in glycemia between a high- vs. low-GI meal test after the lunch meal when compared to the breakfast.…”

“…Monitoring glycemic variability was also a good way to check participants’ adherence to the diet, and our findings confirm that participants indeed adhered to the high-GI or low-GI diets. Previously, differences in the glycemic response have been observed acutely in healthy volunteers after consuming low- compared to high-GI meals [ 13 , 34 , 36 ]. However, the GI of the high-GI diets was higher in these studies.…”

Precision Gestational Diabetes Treatment: Systematic review and Meta-analyses

“…In the non-pregnancy literature, efficacy of dietary interventions has been reported to differ for patients with distinct metabolic profiles, for example high fasting glucose vs high fasting insulin, or insulin resistance vs low insulin secretion [73][74][75] . More recent evidence from appropriately designed, prospective dietary intervention studies has confirmed that dietary interventions tailored towards specific metabolic profiles have more beneficial effects than interventions not specifically designed towards a patient's metabolic profile [76][77][78][79] . Ongoing studies such as the Westlake Precision Birth Cohort (WeBirth) in China (NCT04060056) and the USA Hoosier Moms Cohort (NCT03696368) are collecting additional biomarkers which will enhance knowledge in this field.…”

The association of Carbohydrate Quality Index with cardiovascular disease risk factors among women with overweight and obesity: A cross-sectional study

“…It also affects inflammatory markers such as hs-CRP ( 54 , 56 ). GI, another CQI component, was shown to increase postprandial glucose, insulin responses, TG, and non-HDL cholesterol, and decrease HDL cholesterol ( 60 , 61 ). Whole grains are one of the CQI components that in previous studies was shown to have significant effects on HDL, LDL, TC, HbA1c, and CRP ( 62 ).…”