VANCOUVER – Taking frequent 5-minute breaks from prolonged sitting to stand or walk at a leisurely pace improved the metabolic response to a meal in heavy postmenopausal women with dysglycemia in a randomized trial reported at the World Diabetes Congress.
The incremental area under the curve for glucose levels after a meal was 34% lower with standing breaks and 28% lower with light walking breaks, compared with uninterrupted, prolonged sitting. Moreover, these benefits persisted into the next day.
Findings were similar for levels of insulin (20% and 37% reductions in response) and for the suppression of nonesterified fatty acids (33% and 47% reductions in response).
Dr. Joseph Henson
“The results of this trial provide new experimental evidence that simply breaking up sedentary behavior appears to have quite an acute positive effect in overweight or obese women with a high risk of type 2 diabetes, and it may last for at least 24 hours after the initial activity stimulus,” commented first author Joseph Henson, Ph.D., a research associate at the Diabetes Research Centre at the University of Leicester in England.
“This simple behavioral approach could inform future public health interventions aimed at improving the metabolic profile of dysglycemic individuals if we are able to prove this in large numbers and also in men,” he added.
“I think as a proof of principle, this study was fascinating,” commented session comoderator Dr. Robert E. Ratner, professor of medicine at Georgetown University and senior research scientist at the MedStar Health Research Institute, Washington, as well as chief scientific and medical officer of the American Diabetes Association.
However, the uninterrupted sitting condition was not realistic, he noted in an interview. “The bottom line is that none of us are escorted to the lavatory by wheelchairs, so the control situation is somewhat limited. But I think that it points out that all of us need to sit less and move more.”
A session attendee noted that the findings for simple standing and with regard to the persistence of the effects over time were somewhat surprising.
The “difference I would have thought previously would have been driven by energy expenditure. So I would have said individuals would have to get up and move in order to see a difference,” Dr. Henson acknowledged. “But we were noticing that [benefit] even with standing. So maybe there is something happening at the level of the muscle, which is inducing the responses.”
As for the persistence of the metabolic benefit, more research will be needed, he said. In particular, studies should assess exactly how long it lasts.
“I think the main conclusion is, simply put, that you can break sitting time with anything, whether it’s standing or walking, and you are likely to get some sort of effect,” Dr. Henson said. Also, individuals should “try and use a stepped approach, so going from sitting to standing, and from standing to walking. The more you move, the better the health outcomes will be.”
Women were eligible for the trial if they were overweight or obese, postmenopausal, aged 50-75 years, and had impaired glucose tolerance or a glycated hemoglobin level of 5.7%-6.4%. “These characteristics are really important because these are the sorts of individuals who are likely to be identified and referred into relevant diabetes prevention programs,” Dr. Henson commented. In addition, the women had to be sedentary, engaging in less than 150 minutes of regular purposeful activity each week.
They each participated in two of three activities on separate days: unbroken prolonged sitting for 7.5 hours (interrupted only by trips to the restroom by wheelchair); prolonged sitting, broken up with 5-minute bouts of standing every 30 minutes; and prolonged sitting, broken up with 5-minute bouts of light-intensity walking (up to 2.5 mph) on a treadmill every 30 minutes.
Midway through each day, the women were given a high-fat meal. Serial blood samples were collected throughout the day for measurement of cardiometabolic markers.
Study results, reported at the congress and recently published (Diabetes Care. 2015 Dec 1. doi: 10.2337/dc15-1240), showed that the incremental area under the curve was 5.3 mmol/L per hour with unbroken prolonged sitting, but it was lower at 3.5 mmol/L per hour with standing breaks and 3.8 mmol/L per hour with sitting breaks (P less than .05 for each difference vs. sitting).
Respective values were 548.2, 437.2, and 347.9 mU/L per hour for insulin levels (P less than .05 for each difference vs. sitting), and –1.5, –1.0, and –0.8 mmol/L per hour for suppression of nonesterified fatty acid levels (P less than .05 for each difference vs. sitting).