A study on the effects of a whole grain diet combined with short duration exercise on postprandial glucose levels in overweight and obese adults.

OBJECTIVE: Postprandial glycemic excursions represent a critical determinant of metabolic health in individuals with overweight or obesity. Previous studies have demonstrated that moderate-to-vigorous exercise lasting at least 5 min, initiated 30 min after breakfast, significantly attenuates postprandial glycemic responses and reduces peak glucose levels. However, whether this effect remains consistent across various grain powder based meals is still unclear. This study therefore examined the exercise diet interaction to determine whether 5 min of moderate-to-vigorous exercise performed 30 min after breakfast could elicit a distinct glucose lowering effect depending on the dietary composition.

METHODS: This study adopted a within subject, fixed sequence, repeated measures intervention design. A total of 43 adults with overweight or obesity were enrolled and completed a 15 day dietary and exercise intervention trial. Throughout the experimental period, participants consumed a test breakfast daily consisting of a designated grain powder served with one boiled egg; meanwhile, their remaining dietary intake was not controlled, and they were instructed to maintain their habitual lifestyles. The five grain powders-tartary buckwheat flour, millet flour, oat flour, yam flour and soy milk powder were commercially available products (Joyoung brand) procured by the research team. On the third day of each 3 day breakfast intervention phase, participants performed 5 min of moderate-to-vigorous exercise 30 min after breakfast consumption. The exercise routine comprised jumping jacks, lateral squats, shadow punches, under leg claps, and lateral shuffles. Each movement was executed for four 8 count phrases synchronized with Tabata style music. Demonstration videos of the exercise routine were recorded by the research staff, who also provided instruction and supervised the exercise sessions. Statistical analyses, including non-parametric tests and generalized estimating equations generalized estimating equations (GEE), were performed using SPSS software, and data visualization was conducted using GraphPad Prism.

RESULTS: This study analyzed the main effects of grain powder type and exercise, as well as their interaction, on 2-h postprandial glycemic (2-h PBG) responses using a GEE model. Model effect tests indicated that the type of grain powder significantly influenced postprandial glycemic parameters, including the incremental area under the curve (iAUC; Wald χ2 = 64.997, p < 0.001), peak glucose increment (Wald χ2 = 45.989, p < 0.001), and glycemic variability (GV) (Wald χ2 = 86.352, p < 0.001). Neither the main effect of exercise nor the powder-exercise interaction was statistically significant (all p > 0.05). Soy milk powder elicited the lowest iAUC (51.494 ± 6.335, 95% CI: 39.078-63.911), which was significantly lower than those following the consumption of oat powder (107.421 ± 10.591, 95% CI: 86.662-128.179), millet powder (95.319 ± 10.078, 95% CI: 75.567-115.071), and tartary buckwheat powder (93.542 ± 8.031, 95% CI: 77.801-109.283; all p < 0.01). Additionally, soy milk powder resulted in the lowest peak glucose increment (1.194 ± 0.101, 95% CI: 0.997-1.391) and GV (0.068 ± 0.004, 95% CI: 0.060-0.076). By contrast, yam powder yielded a significantly lower overall glucose area under the curve (AUC; 746.773 ± 13.669, 95% CI: 719.982-773.563) compared with tartary buckwheat powder, millet powder, and oat powders (all p < 0.05).

CONCLUSION: Within the present study context, the type of grain powder was identified as the primary factor influencing postprandial glycemia in adults with overweight or obesity, whereas neither the short bout of moderate-to-vigorous exercise nor the exercise-powder interaction achieved statistical significance. Soy milk powder elicited the lowest iAUC, peak glucose increment, and GV, a favorable glycemic profile largely attributable to its low carbohydrate and high protein composition. These findings suggest that incorporating high protein, low glycemic index options such as soy milk powder into breakfast may favorably modulate acute postprandial glycemic responses.