Overweight patients with diabetes or impaired glucose tolerance who had moderate glycemic levels prior to starting a short-term workout program achieved better glycemic control than those with higher glycemic levels at baseline, researchers found.
Patients with oral glucose measures less than 13.1 mmol/L and who had a hemoglobin A1c (HbA1c) level less than 6.2% prior to a 12- to 16-week exercise program showed significant improvement in post-exercise 2-hour glucose level (P<0.001) and significant decrease in post-exercise HbA1c (P=0.005), according to Thomas Solomon, PhD, of the Center of Inflammation and Metabolism at Rigshospitalet in Copenhagen, Denmark, and colleagues.
Study participants with elevated oral glucose -- above 13.1 mmol/L -- and elevated HbA1c -- greater than 6.2% -- prior to the exercise intervention saw smaller improvements after training, they wrote online in JAMA Internal Medicine.
Prior research has shown associations between aerobic exercise training and improve glycemic control in patients with diabetes, but variance between patients was large, the authors noted.
They studied whether improvements in glycemic control after a 12- to 16-week aerobic exercise intervention were tied to glycemic control prior to the aerobic training in a population of 105 older, overweight or obese adults with impaired glucose tolerance or diabetes.
Participants received measures of body composition, aerobic fitness via maximal oxygen uptake, HbA1c, fasting glucose, and oral glucose tolerance test scores prior to and following the exercise intervention, while the relationships between the "before" and "after" measures were assessed through linear and nonlinear regression.
Prior to the intervention, participants had a body mass index of 33, were a mean 61 years old, and were mostly comprised of those with impaired glucose tolerance (56 patients) versus diabetes (49 patients).
Following the 3 to 4 months of aerobic training, patients lost a mean 4.6 kg, reduced whole-body adiposity by a mean 1.9%, lowered fasting glucose by a mean 0.35 mmol/L, lowered 2-hour glucose by a mean 0.8 mmol/L, and improved oxygen uptake by a mean 0.23 L/min. Fasting glucose pre-training did not significantly affect changes in glycemic control after the intervention period.
There was a nonlinear trend for pre-training 2-hour oral glucose and exercise-induced change in 2-hour oral glucose (P=0.06), which was significant in those with pre-training oral glucose lower than 13.1 mmol/L, and remained a trend among those with pre-training 2-hour oral glucose greater than 13.1 mmol/L (P=0.07).
In addition, HbA1c had a similar, but significant, nonlinear quadratic relationship with pre- and post-training HbA1c (P=0.02). Those with HbA1c of 6.2% prior to the intervention showed a significant exercise-induced decrease in HbA1c post intervention (P=0.005), while those with HbA1c greater than 6.2% also had a significant improvement in HbA1c after the 12 to 16 weeks of training, though the effect was not as large (P=0.04).
The authors also noted that pre-training HbA1c was "linearly and inversely related to the exercise-induced change in oxygen uptake, such that high pre-training HbA1c level predicted smaller exercise-induced increases" in oxygen uptake (P=0.006).
"Although moderate-intensity aerobic exercise can improve glycemic control, individuals with ambient hyperglycemia are the most likely to be nonresponders," they concluded.
Stephen Hammes, MD, PhD, of the University of Rochester Medical Center, commented that he found the results of the study beneficial, but that additional research should look for the source of the interaction.
"What I think is important is to determine why some people benefit so much from diet and exercise and why others don't," Hammes told MedPage Today in an interview. He added that, "This study suggests that there is a difference, but doesn't explain why that difference is."
The study was funded through the European Foundation for the Study of Diabetes, the National Institutes of Health, and the Clinical and Translational Science Award.
The authors declared no conflicts of interest.
- Reviewed by Zalman S. Agus, MD Emeritus Professor, Perelman School of Medicine at the University of Pennsylvania and Dorothy Caputo, MA, BSN, RN, Nurse Planner