Reduced Exercise and its Effect on Glycemic Control in Healthy People

Involvement in physical activity is known to improve the control of glucose levels in blood. However, very few studies have been conducted so far to examine the effect of reduced physical activity on glycemic control. In the present study, healthy volunteers were made to reduce their physical activity, and then a continuous evaluation of their blood glucose levels was performed. During the period of reduced physical activity, the levels of postprandial (after meals) blood glucose levels were significantly high, compared to those during regular physical activity.

The incidence of diabetes is increasing rapidly in the U.S. Currently, over 79 million people in the U.S. alone have blood glucose levels above normal limits. It is estimated that by the year 2050, one in every three individuals would be diabetic in the U.S. Elevated postprandial blood glucose level is an important indication of the onset of diabetes. Elevated postprandial blood glucose level can cause harm to coronary blood vessels in the heart. Hence, there are many studies being conducted worldwide to develop strategies of early detection and prevention of diabetes in the community. This study was done on healthy volunteers to assess the effects of physical inactivity on postprandial glycemic control.

* This study involved 12 healthy volunteers aged between 20 and 35 years. Their physical activity was measured by a pedometer. Only those who walked more than 10,000 steps per day were included.
* First, the participants were supplied with a pedometer and a device that measured the number of steps and the duration spent on walking, running, and climbing stairs. Then, participants were asked to maintain their usual physical activity for 3 days during which their glucose levels were monitored. Blood glucose levels before meals and then 30, 60, 90, and 120 minutes after meals were taken. On the fourth day, a glucose tolerance test was done during which the participants consumed large amounts of glucose. The levels of glucose, insulin, cortisol, and growth hormone were then assessed.
* In the second part of the experiment, the same procedure was repeated. However, this time, the participants were asked to refrain from physical activity as far as possible.
* Levels of postprandial blood glucose levels and the results of glucose tolerance tests, in both the situations, were then compared.

* During the first part of the experiment, participants walked 12,956 steps on an average, while in the second part, the number of steps decreased to 4,319.
* A significant increase was observed in the postprandial glucose levels after three days of reduced physical activity. The duration of elevated glucose levels in blood was also high in the decreased physical activity condition.
* The results of the glucose tolerance test revealed that in the reduced physical activity state, the levels of insulin were significantly elevated. There were no significant differences in the levels of cortisol and growth hormone.

Shortcomings/Next steps
A small sample size is the major limitation of the present study. Moreover, this study was carried out in a specific age group of individuals. Hence, further studies involving larger number of participants, with varied ages, are necessary to confirm the findings. In the present study, only the effect of three days of reduced activity was assessed. It is necessary to find out the effects of long-term inactivity.

The authors of this study summarize their findings thus: physical activity plays a fundamental role in the day-to-day maintenance of postprandial glucose and glycemic control, and change in postprandial glucose levels in response to reductions in physical activity occurs rapidly. When measuring the glycemic control, physical activity must be kept in mind before arriving at any conclusions. Elevated levels of insulin in the glucose tolerance test indicate that the body is insensitive to insulin when in a state of decreased physical activity. Hence, it needs more insulin to handle the same amount of glucose. Involvement in vigorous physical activity at least once a day immensely helps in controlling postprandial glucose levels, thereby preventing the development of diabetes in future.

For More Information:
Lowering Physical Activity Impairs Glycemic Control in Healthy Volunteers
Publication Journal: Medicine & Science in Sports & Exercise, 20 June 2011
By Catherine R. Mikus; Douglas J. Oberlin; University of Missouri, Columbia

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