While the researchers caution their results should now be confirmed by trials in larger groups, they suggest three short bouts of exercise a day are more likely to help older people control blood sugar than one long one, especially if timed correctly.
Taking a rest after meals is the worst thing to do, say researchers from George Washington University School of Public Health and Health Services (SPHHS) who led the study and report it in an early issue of Diabetes Care published online this week.
Instead, those who walk the dog, or take the opportunity to run an errand, or just walk at an easy to moderate pace for 15 minutes, are more likely to be the ones who prevent elevated blood sugar, a pre-diabetic condition that over time can develop into full-blown type 2 diabetes.
Estimates suggest about 79 million Americans have pre-diabetes, but most are not aware of it or the risk it poses.
Other studies have found weight loss and exercise can prevent type 2 diabetes, and the exercise does not have to be extreme. For example, earlier this year researchers reported that brisk walking can reduce a person's risk of diabetes, high blood pressure, and high cholesterol just as much as running can.
But this is the first study to look at the effect of taking short bouts of exercise around the risky period following meals, when blood sugar can rise rapidly and cause damage.
In a statement, lead author Loretta DiPietro, chair of the Department of Exercise Science at SPHHS, says:
"These findings are good news for people in their 70s and 80s who may feel more capable of engaging in intermittent physical activity on a daily basis."
Walking Helps Reduce Older People's Insulin ResistanceOlder people may be less able to control blood sugar after meals because of insulin resistance in the muscles and slow or low insulin secretion from the pancreas. The body needs insulin to regulate blood sugar.
High blood sugar after meals is a key risk factor in moving from impaired glucose tolerance to type 2 diabetes and heart disease, says DiPietro.
She and her colleagues found three short walks after meals were as effective at reducing blood sugar over 24 hours as a 45- minute walk of the same easy-to-moderate pace.
Also, post-meal walking was significantly more effective at lowering blood sugar for up to three hours following the evening meal.
"The muscle contractions connected with short walks were immediately effective in blunting the potentially damaging elevations in post-meal blood sugar commonly observed in older people."
Taking a Rest After Meals Is Not AdvisableBut walking after meals is not what most older people do, says DiPietro. Most of them take a nap or watch TV after a big afternoon or evening meal.
"That's the worst thing you can do," she says, advising instead to "let the food digest a bit and then get out and move".
A short walk after the big evening meal is particularly important because their findings suggest high post-dinner blood sugar is a strong determinant of excessive 24-hour glucose levels, she adds.
Small Study Compared Effect of Three Walking Programs On Blood SugarFor their study, DiPietro and colleagues recruited ten people aged 60 and older who were at risk for type 2 diabetes due to insufficient physical activity and higher-than-normal fasting blood sugar. Otherwise they were healthy non-smokers.
The participants underwent three exercise programs, four weeks apart. The order in which they did the programs was random.
Each program required a 48-hour stay in a "whole-room calorimeter", a closed room that allows researchers to measure the person's energy expenditure and ability to burn different fuels by sampling the air and measuring oxygen consumed and carbon dioxide produced.
The first 24 hours of each stay was a "control day". On the second day, participants carried out one of the three exercise programs: they either walked for 15 minutes after each meal; or walked for 45 minutes at 10.30 am; or walked for 45 minutes at 4.30 pm.
The participants had standardized meals and had their blood sugar measured continuously throughout the 48 hours. And they did their walking on a treadmill at an easy-to-moderate pace.
Walk After Evening Meal Was the Most EffectiveFrom the results, the researchers suggest the most effective post-meal walk is probably the one after the evening meal.
DiPietro says they observed how the rise in blood sugar after the evening meal, which is often the largest in the day, often lasted well into the early hours of the next morning. Yet it "was curbed significantly", as soon as the participants started walking on the treadmill.
Although they monitored blood sugar continuously and controlled the participants' environment carefully, this was a small study and the results now need to be confirmed in larger trials with more people, warns DiPietro.
Last year, another study published in Diabetes Care, found that whether or not your neighborhood is good for walking around could influence your risk for diabetes.
Written by Catharine Paddock PhD