Lowering glycemic index (GI) led to improved contol of blood sugar, better insulin sensitivity, and weight loss in people with type 2 diabetes given group education sessions, according to researchers at Pennsylvania State University.
As background, the scientists note that:
GI may play a role in preventing or treating type 2 diabetes by decreasing the risk for obesity or by altering metabolic endpoints. Improvements in glycaemic control were observed in people with diabetes in a recent meta-analysis. A lower-GI diet was shown to decrease postprandial glucose [blood sugar after meals] and insulin responses and improve serum lipid concentrations. Lower-GL [glycemic load] diets were associated with decreased risk for type 2 diabetes, decreased levels of C-reactive protein and inflammation, and weight loss.
Ninety-nine test subjects completed the study that enrolled adults 40 to 70 years old who had diabetes at least one year but were not taking insulin shots. Average body mass index was 33, so they were obese. Average weights were 84.5 kg (186 lb) for women and 108.7 kg (239 lb) for men. Average baseline hemoglobin A1c was estimated at 7%, so these folks were under good glucose control. Baseline carbohydrate intake was 45% of total energy, a bit lower than the general population.
The 9-week intervention involved nine weekly group education sessions—lasting 1.5 to 2 hours—focusing on selection of lower-GI (vs higher-GI) foods instead of restricting carbohydrates. Also covered were monitoring of portion sizes to control carb consumption, carb counting to control carb distribution and intake, and self-monitoring of food intake.
Although weight loss was not a goal, weights fell by 1-2 kg (2-4 pounds). Men lost more than women. Overall diet glycemic index fell by 2-3 points (a modest amount). Comparing values before and after intervention, fasting glucose and postprandial glucose fell significantly, and insulin sensitivity improved. Although not measured, the authors estimate hemoglobin A1c levels would have fallen an absolute 0.3%, based on measured glucose levels. Percentage of calories from carbohydrate did not change.
This is one of the few studies to try low-glycemic index behavioral intervention in adults with type 2 diabetes. Results are encouraging.
The researchers and I wonder if results would have been even more dramatic if the test subjects hadn’t been so well controlled before intervention or if they had dropped their glycemic index even lower. Probably so. Many people with type 2 diabetes have hemoglobin A1c’s well over 7%.
The researchers attribute the weight loss to portion control and simple self-monitoring of consumption.
For people with diabetes, this study supports selection of lower-glycemic index instead of higher-GI. In fact, we’d see less diabetes, heart disease, breast cancer, and gallbladder disease if all women—diabetic or not—ate lower-GI.
Reference: Gutschall, Melissa, et al. A randomized behavioural trial targeting glycaemic index improves dietary, weight and metabolic outcomes in patients with type 2 diabetes. Public Health and Nutrition, 12(2009): 1,846-1,854.