Dr. Yogish Kudva, who led the study at Mayo Clinic in Rochester, Minnesota, stated that, "Minimal activity sustained for 30 minutes (walking 0.7 miles in 33 minutes) lowers post-meal glucose concentrations. Such activity has little or no risk for almost everybody."
The results are from a larger study on patterns of postprandial glucose tolerance.
Dr. Kudva and his team examined 24 study participants: 12 with type 1 diabetes and 12 healthy controls.
For three days and four nights, the researchers monitored the participants' diet and calorie intake, physical activity and glucose levels in a controlled environment. Implanted continuous glucose sensors measured glucose levels and wearable triaxial accelerometers reported body positions and movement to measure activity.
The participants walked after two of their daily meals and sat after a randomly designated third meal. When walking, they walked and rested in intervals, moving for 33.5 minutes and sitting for 26.5 minutes. In total, the participants walked for five to six hours every day at 1.9 kmph (1.2 mph), for a total of roughly 5.6-6.7 km (3.5-4.2 miles) in each 24 hour period.
The researchers reported data for the glucose measurements taken 4.5 hours after eating. At that interval, healthy people had a 113% increase in glucose levels after inactivity compared to when they walked (p=0.024). Their incremental glucose area above basal was 4.5 mmol/L at 270 minutes with exercise and 9.6 mmol/L at 270 minutes after inactivity.
The diabetes patients had 145% higher glucose after inactivity compared to when they walked (p<0.001). After walking, their incremental glucose area above basal was 7.5 mmol/L/270 minutes. And after inactivity, it was 18.4 mmol/L/270 minutes.
Substituting other activities such as washing the dishes after a meal could have similar effects to walking, the researchers suggest in their paper.
Dr. Kudva mentioned that, "In general, walking improved glucose after about 10 minutes with the improvement lasting until five minutes after such activity ceased."
He added, "The improvement in glucose was about 30 mg/dl or 1.75 mmol/L. Since we have multiple glucose measurements over an extended period of time, we can only provide approximate numbers."
What are the possible long-term benefits for healthy people of walking or doing light exercise after meals? "This is a more complicated question," Dr. Kudva said. "A Lancet paper from 2011 indicates significant benefits from walking over the long term. They did not look specifically at meal-related walking but we have no reason to think that the health benefits would not occur when walking is undertaken after meals. Benefits would include weight and body mass index being more healthy and likely less cardiovascular events and all-cause mortality."
The authors write in their paper that the findings may help them develop closed-loop algorithms for an artificial pancreas system.
Diabetes Care published online Aug 8, 2012