Responses to oral glucose challenge differ by physical activity volume and intensity : a pilot study.

Background: One hour postprandial hyperglycaemia is associated with increased risk of type 2 diabetes and cardiovascular disease. Physical activity has short-term beneficial effects on post-meal glucose response. This study compared the oral glucose tolerance test results of 3 groups of people with habitually different levels of physical activity. Methods: Thirty-one adults without diabetes (age 25.9 ± 6.6 years; body mass index 23.8 ± 3.8 kg.m-2) were recruited into 3 groups based on self-reported physical activity volume and intensity: Low Activity = < 30 min.day-1 of 'moderate' intensity activity (n = 11), Moderately Active = ≥ 30 min.day-1 of 'moderate' intensity physical activity (n = 10), and Very Active = ≥ 60 min.day-1 of 'intense' physical activity (n = 10). Participants completed an oral glucose tolerance test (50 g glucose) with capillary blood samples obtained at baseline, 15, 30, 45, 60, 90 and 120 minutes post-ingestion. Results: There were no significant differences between groups for age or percentage body fat or glycated haemoglobin (p> 0.05). The groups were significantly different in terms of baseline glucose, gender and BMI and this was accounted for in the analysis. There was a statistically significant effect of physical activity on the one hour postprandial glucose results (p=0.029), with differences between Very Active and Low Activity (p=0.008) groups but not between the Moderately Active and Low Activity groups (p=0.360), even when baseline glucose and gender differences were accounted for. For iAUC there was no significant effect of activity group once gender and bodyfat % had been accounted for. Those in the Low Activity group took an average 13.2 (95% CI: 2.8 – 23.5) minutes longer to reach peak glucose level than those in the Very Active group and this was significant (p=0.015). Conclusion: The results suggest that high levels of physical activity have a beneficial effect on postprandial blood glucose profiles when compared to low and moderate levels of activity.