Local foods with low glycaemic index improve glucose response, promote fat oxidation
A low glycaemic index (GI) meal plan consisting of commonly consumed foods in Asia yields reductions in glycaemic response and variability over 24 hours, as well as promotes fat oxidation, in sedentary, normal-weight men, according to a team of Singapore-based researchers.
In a randomized, cross-over trial including 11 Asian men (mean age 24.5 years; mean body mass index, 21.9 kg/m2; mean HbA1c, 5.1 percent) who followed both a 1-day low GI and 1-day high GI diet, outcomes including 24-hour glycaemic response and variability and substrate oxidation were more favourable during the low GI diet. [Nutr J 2017;16:43]
Based on data generated from continuous blood glucose monitoring, the low GI diet particularly resulted in lower 24-hour glucose incremental area under the curve (iAUC; 860vs 1,329 mmol/L.min; p=0.014) with lower postprandial glucose iAUC after breakfast (p<0.001), lunch (p=0.009), snack (p=0.012) and dinner (p=0.003). The mean amplitude of glycaemic excursion over 24 hours was also lower during the low vs high GI diet (1.44 vs 2.33 mmol/L; p < 0.001).
At the same time, the low GI diet yielded a smaller decrease in 10-hour fat oxidation (as evaluated using whole body calorimeter; −0.033 vs −0.050 g/min; p<0.001), especially after breakfast (p<0.001) and lunch (p<0.001).
Taken together, the reduced glucose response and higher fat oxidation rate in response to low GI meals imply that the reduced fat deposition during a low GI diet is driven by increased fat oxidation, researchers explained.
“Notably, over 10 hours, low GI meals resulted in an increased oxidation of 4.7 g of fat, which translate to around 42 kcals burned from fat, which could accumulate to around 300 kcals per week. It must be noted that the increased energy expenditure is lower when decreased carbohydrate oxidation is taken into account,” they added.
“Even in a sedentary state, a low GI diet based on locally available foods, not only lowers blood glucose but also enhances fat oxidation and may play a key role in weight regulation and maintenance,” given that it may take only an excess of 7.5 kcal per day to explain the current epidemic of obesity, as has been demonstrated in a previous study, researchers pointed out. [Lancet 2011;378:826–837]
Among the locally consumed foods selected to construct the low GI test meals were low-fat milk and lemon puff biscuits for breakfast; thin rice vermicelli, teriyaki chicken and fresh spinach for lunch; kaya butter toast and Milo for snack; and parboiled basmati rice, chicken stock, fresh spinach and teriyaki chicken for dinner. These meals matched the daily energy requirements (based on the measured basal metabolic rate) of the study participants.
“Our observations provide public health support for the encouragement of healthier nutrition choices by consuming low GI foods,” researchers said. This is especially important since the Asian phenotype has been shown to be more susceptible to diabetes compared with Caucasians. [Diabet Med 2010;27:1205–1208; Adv Food Nutr Res 2015;75:97–154]
“Additionally in Asia, people predominantly live on a high glycaemic, high carbohydrate diet and are thus susceptible to weight gain and obesity similar to observations from animal studies,” they noted.
Further research is needed to elucidate the link between blood glucose levels and fat oxidation in order to determine how insulin and other hormones may play a role in tissue accretion and substrate oxidation, researchers added.