By Brian Lau, M.D.
A 15-minute walk after every meal - that's what a new study says can lower blood sugar and the risk of type 2 diabetes.
What's more, it's better than 45 minutes of sustained walking in the morning or afternoon.
Elevated blood sugars, particularly after meals, can lead to diabetes, which doctors are expecting to see more and more of as the overweight age.
According to the U.S. Centers for Disease Control and Prevention, type 2 diabetes affects 25.8 million Americans. It's the leading cause of kidney failure, lower limb amputations that aren't because of accident trauma, and new cases of blindness among adults in the United States. Diabetes is a major cause of heart disease and stroke - and, all by itself, is the seventh leading cause of death in the United States.
In a study published Wednesday in the journal Diabetes Care, researchers monitored blood sugar levels in healthy adults with an average age of 70 who were at risk of impaired glucose intolerance, a precursor of diabetes. Each study participant tried out three different exercise regimens on different days: Some did a 15-minute, post-meal walk (three meals per day, three walks per day), one 45-minute morning walk and a 45-minute afternoon walk.
The winner in terms of lower blood glucose levels? The after-meal walk.
"A post meal walk is timed to when blood glucose just starts to climb," said Dr. Loretta DiPietro, lead author of the study and chair of the Department of Exercise Science at The George Washington University School of Public Health and Health Services. "The muscle activity and the muscle contractions help to clear glucose.
"It's like another set of hands to help the pancreas halt the surge of glucose."
Blood sugar levels are the highest after meals, and as we age our pancreas is less effective in releasing insulin, a hormone that helps lower blood sugar. That leads to even higher blood sugars that can increase the risk of diabetes.
This type of short, low-stress exercise is not going to make you aerobically fit.
"This [post-meal walking] most benefits middle-aged, obese people who are showing signs of pre-diabetes, or older people [for whom] one giant bout of exercise may be too stressful," DiPietro said. "It also has applications to pregnant women at risk of gestational diabetes, especially later in term when it may be difficult for 45 sustained minutes of activity."
She stressed that because of the low level of exercise, it must be maintained at least three times every day.
"People will not get the benefit if they miss times," DiPietro said.
Other specialists were more cautious in their interpretations of the study's findings.
"Exercise three or four times a day may be better, but it is not practical for all patients," warned Dr. Joel Zonszein, a professor at Albert Einstein College of Medicine and director of the Clinical Diabetes Center at Montefiore Medical Center.
In addition to the difficulty of maintaining that level of frequency of exercise, Zonszein pointed out that for some patients the large metabolic activity used by the gastrointestinal system following a meal may make it more difficult to exercise. He suggested patients, "stay within their means."
He highlighted that exercise and diet are more effective in the elderly to prevent diabetes and stressed the most important suggestion is "to keep on moving" regardless of the timing of the exercise.
Short walks of 15 minutes may be better at reducing the risk of developing diabetes, but it is most important to exercise daily, regardless of its timing.