Going for a brisk walk after a meal may be an effective means of keeping diabetes at bay in older people, a study suggests.
Earlier research has indicated that maintaining a healthy weight and getting regular exercise can help to prevent diabetes in people who are prone to the condition.
"But this is one of the first studies to consider the timing of the exercise … and the benefits are just enormous," said the lead researcher, Loretta DiPietro, a professor and chair of exercise science at the George Washington School of Public Health and Health Services in Washington, D.C.
The findings suggest that a walk after a meal can stabilize levels of glucose in the the bloodstream. Huge swings in blood-glucose levels, a hallmark of diabetes, can damage blood vessels and eventually contribute to the development of cardiovascular disease, DiPietro explained. So it is critically important to keep glucose levels on a relatively even keel, she said.
Glucose (or sugar) is normally moved into body tissues from the bloodstream by insulin, a hormone produced in the pancreas. In healthy individuals, the amount of insulin that is secreted by the pancreas varies in order to keep blood sugar at a steady level.
But people with type 2 diabetes do not make enough insulin or their bodies do not respond properly to the hormone – a condition known as insulin resistance.
DiPietro noted that the risk of developing diabetes increases significantly in older individuals, particularly those in their 70s and 80s.
"As part of the aging process, muscles become resistant to insulin. But also what happens is that the pancreas becomes really sluggish at putting out insulin. So you got this double whammy going on," she said. "And, in older people, the amount of insulin their body is able to produce tends to dip in the later part of the afternoon."
That essentially means that the body's insulin production cannot meet the challenge of processing dinner, which, for many people, is the biggest meal of the day. As a result, they go to bed with high levels of glucose still in their bloodstream.
People who are at risk of type 2 diabetes – such as those who are overweight or already showing signs of insulin resistance – are usually told to exercise regularly as a way of stabilizing their blood-glucose levels. The typical recommendation calls for 45 minutes of moderately strenuous activity each day.
However, many people find it hard to complete 45 minutes of sustained exercise daily. So DiPietro and her colleagues decided to see what would happen if those 45 minutes were broken up into three 15-minute segments spread over the course of the day – shortly after breakfast, lunch and dinner.
For the study, the researchers recruited 10 volunteers – aged 60 and older – who were in good health but deemed to be at an elevated risk of type 2 diabetes. All the participants completed three exercise protocols. Each of those protocols involved a 48-hour stay in a research lab.
The first day of each protocol served as a control period in which the volunteers rested and their blood-glucose levels were monitored.
On the second day, the participants performed one of three exercise routines: 45 minutes of sustained walking at 10:30 in the morning; or 45 minutes of sustained walking at 4:30 in the afternoon; or three separate walks 15 minutes in duration after each meal. The walking was performed on a treadmill at an easy-to-moderate pace.
The findings, published in the journal Diabetes Care, revealed that three short post-meal walks were just as effective as one 45-minute walk for reducing the average blood-sugar levels over a 24-hour period.
But more important, the post-meal walks did a much better job than sustained walking at eliminating high blood-sugar levels at the end of the day. "We demonstrated that post-meal exercise really prevented these people from going to bed with very high blood-sugar levels."
Basically, a post-meal walk provides a blood-glucose-stabilizing influence when it is needed the most – just as the glucose is flooding into the bloodstream from the meal.
DiPietro said the walk should be started about 30 minutes after the meal. By that time, the digestive process is well under way and the nutrients are starting to be absorbed into the bloodstream. "This is when you see a massive rise in blood-sugar levels," she said. "And the muscle contractions, all by themselves, will help clear the glucose."
She explained that the contractions lead to the release of tiny proteins – called glut4 transporter proteins – that help escort the glucose into muscle cells.
More studies will have to be done before researchers can say with certainty that post-meal exercise can help to prevent diabetes. Still the results of the new study seem promising. "The findings have tremendous public-health importance in that they offer powerful evidence that smaller doses of exercise repeated several times per day have greater overall benefit to blood-sugar control among older people than one large sustained dose – especially if those short bouts are timed just right," the research team said in a statement released with the study.
DiPietro believes that it should be relatively easy for older people to incorporate this exercise strategy into their daily lives. "People take short walks all the time," she said. "If they have a pet, they could take it for a walk. Or do an errand. And if they time the exercise for when it's most need – after a meal – it will help clear the insulin from the blood."