Exercise at lunchtime: effect on glycemic control and oxidative stress in middle-aged men with type 2 diabetes

Purpose Postprandial hyperglycemia and glycemic oscillations have been associated with increased oxidative stress. We sought to investigate the effect of two walking exercise protocols performed during lunchtime on glycemic control and oxidative stress in type 2 diabetic (T2D) patients. Methods Nine T2D patients participated in three randomized crossover trials; a control trial (Con), with participants having a standard lunch followed by their normal daily activities and two exercise trials (ContEx and Splitex). In ContEx, subjects performed 40 min of brisk walking 40 min after lunch, whereas in SplitEx the walking exercise was divided in two 20-min isoenergetic bouts, before and 40 min after meal. 24-h glycemic control was monitored by continuous glucose monitoring. 24-h urinary levels of 8-iso PGF2ɑ were measured as a marker of oxidative stress. Results SplitEx resulted in less time spent in moderate hyperglycemia after lunch vs ContEx (42.4 ± 38.7 % vs 68.2 ± 32.7 %, P = 0.04). ContEx reduced hyperglycemic time after breakfast consumed the morning after the exercise session (58.3 ± 29.6 Con vs 40.2 ± 33.4 % ContEx, P = 0.02). Compared with Con, 24-h urinary isoprostanes were decreased both in ContEx (−68 %, P = 0.02) and SplitEx (−63 %, P = 0.04). Conclusions Splitting an exercise session into two bouts, pre- and post-lunch, affects mainly the glycemic response to lunch, while a single-continuous isoenergetic session exerts its effect later in the 24-h period. Both exercise modalities effectively attenuate systemic oxidative stress with similar overall benefits.