In 2002, the Diabetes Prevention Program (DPP) found that a combination of a low-calorie, low-fat diet plus exercise reduces the risk of diabetes more than metformin (a blood-sugar-lowering drug) or a placebo in people at high risk for the disease. Seven years after the three-year trial ended, the weight loss and exercise were still paying off.
Among 1,416 women in the DPP who had no history of diabetes during pregnancy, those who had been in the weight loss + exercise group had a 30 percent lower risk of being diagnosed with diabetes since the study ended than those who got metformin or the placebo.
Among 350 women who did have a history of diabetes during pregnancy, those who had been in either the metformin or weight loss + exercise group had about a 35 percent lower risk of diabetes than the placebo takers.
What to do
Lose (or don’t gain) excess weight and aim for about five hours of exercise each week.
Do I have to exercise to reduce diabetes risks?
“If people don’t stay physically active as they get older, their muscles become insulin resistant,” says Loretta DiPietro. That means their insulin does a poor job of moving blood sugar into their muscle cells.
“And when people reach their 70s, the pancreas doesn’t work as well as it used to, so insulin secretion becomes sluggish,” adds DiPietro, who heads the exercise and nutrition sciences department at George Washington University.
With less or less effective insulin, blood sugar levels stay elevated for a longer time after a meal, and even fasting blood sugar creeps up over the years.
“Exercise is very effective at improving insulin sensitivity in the muscles,” DiPietro explains. (What’s more, when you exercise your muscles contract, which lets them take in blood sugar even without insulin.) This is one reason people are encouraged to exercise to reduce diabetes risks.
“So we thought, Why not exercise when it’s needed the most, about a half hour after people finish eating?” says DiPietro. That’s when digested food gets absorbed into the bloodstream. “It’s the perfect time to use muscle contractions to help clear glucose from the blood.”
Walking is a great exercise to reduce diabetes risks
DiPietro and her colleagues recruited 10 sedentary older adults who had pre-diabetes to go for a short (15-minute) walk after breakfast, lunch, and dinner or a long (45-minute) walk either at 10:30 a.m. or at 4:30 p.m.
“It was all barely moderate-intensity walking, about 3 miles per hour on a treadmill,” says DiPietro.
Both the three short walks after meals and the one long morning walk helped control blood sugar levels throughout the day, lowering the A1c average to 6.5 mmol/L instead of about 7.1 on the days they didn’t walk. In contrast, the late afternoon 45-minute walk had a smaller impact (which wasn’t statistically significant in this small study).
“The only catch is that on the days you don’t do the three 15-minute walks, you don’t get the benefit,” cautions DiPietro, who notes that “you can use a 15-minute bout to walk a dog or run an errand.”
One advantage of the longer walk: as long as you’re walking briskly, you may not have to do it every day.
“If you can consistently walk briskly for 45 minutes to an hour, it would train your muscles to clear glucose more efficiently, so that you might be able to skip a day or two every week.”
But no matter how you choose to walk, “doing it consistently may delay the onset of type 2 diabetes.”
Sources: J. Clin. Endocrinol. Metab. 2015. doi:10.1210/jc.2014-3761. Diabetes Care 36: 3262, 2013.