When Workouts Can't Burn the Sugar

Type 2 diabetes patients with hyperglycemia unable to improve blood sugar with exercise

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) Exercise has been known to help prevent type 2 diabetes. But certain patients with the condition might not get the same results as others.

A new study found that exercise improved blood sugar levels in patients with type 2 diabetes, but changes were limited if patients had abnormally high blood sugar levels, or hyperglycemia.

According to the researchers, these findings highlight the need to better understand who can benefit most from exercise in controlling blood sugar levels.

"Talk to your doctor before starting any serious exercise program."

Thomas Solomon, PhD, from the Centre of Inflammation and Metabolism in Copenhagen, Denmark, led this study to investigate how aerobic exercise could improve blood sugar levels, or glycemic control, in patients with type 2 diabetes.

In type 2 diabetes, the body has difficulty processing blood glucose, or blood sugar, because it does not use insulin properly. As a result, glucose levels rise higher than normal.

So, a crucial part of managing diabetes is managing blood glucose levels.

This study included 105 participants who took part in a 12- to 16-week aerobic exercise program. Participants were 61 years old on average, were overweight or obese and had impaired glucose tolerance or type 2 diabetes. 

The researchers measured participants' fitness level and body composition, which is comprised of bone, muscle and fat. Measurements were taken before they started the exercise routine and after completing the program.

Each person's glycemic control, glucose level after fasting and oral glucose tolerance were also measured.

After completing the exercise program, average body weight, body fat, fasting blood sugar and oral glucose tolerance significantly improved, the researchers found.

Blood sugar is measured by looking at levels of hemoglobin A1C (HbA1c). HbA1c measurements show a person's blood sugar levels over the previous three months.

Participants who had an HbA1c level of less than 6.2 percent prior to exercise saw results after completing the program.

At the same time, changes in glycemic control caused by exercise were reduced if participants had hyperglycemia, or high blood glucose, prior to starting the exercise program.

Hyperglycemia is defined as having a blood sugar level of about 200 milligrams per deciliter, or 11 millimoles per liter.

Hyperglycemic individuals who had an HbA1c level greater than 6.2 percent before starting the exercise program had smaller exercise-induced improvements in HbA1c level.

These participants were called non-responders, or those who did not see improvements from exercise. 

"These findings emphasize that exercise-induced improvements in glycemic control are dependent on the pretraining glycemic level," the researchers wrote in their report.

"We demonstrate that although moderate-intensity aerobic exercise can improve glycemic control, individuals with ambient hyperglycemia are the most likely to be nonresponders," they wrote.

This study was published July 1 in JAMA Internal Medicine.

No conflicts of interest were reported. Grants from the European Foundation for the Study of Diabetes, the National Institute of Health and a Clinical and Translational Science Award supported the study.

Reviewed by: 
Review Date: 
July 3, 2013
Last Updated:
July 30, 2013