Fitness Test May Miss Benefits of Exercise for Diabetics

Marcia Frellick

June 25, 2015

Exercise can help diabetic patients reduce waist circumference and body fat and improve HbA1c levels, even if cardiorespiratory fitness doesn't improve, new data show.

Typically, fitness is judged by how well the body trades oxygen for carbon dioxide when a patient runs on a treadmill. But that definition may be too narrow, at least for diabetic patients, say Ambarish Pandey, MD, a fellow in the division of cardiology at University of Texas Southwestern Medical Center in Dallas, and colleagues. Their findings were published online June 17 in Diabetes Care.

"For patients with diabetes, we need to have more than one target for improvement," Dr Pandey told Medscape Medical News.

Previous research has shown that 30% of people won't expand their oxygen capacity, no matter how much they exercise.

In this study in type 2 diabetes patients, that number was even higher: 43% of study participants showed no improvement in fitness after exercise training. But those nonresponders (those whose ability to take in oxygen did not improve) were still able to significantly improve glycemic control with exercise, which was linked with reductions in body fat.

How to Talk to Patients About Exercise

Current public-health recommendations say people should do a minimum of 30 minutes of moderate-intensity activity most days of the week to improve cardiorespiratory fitness. But a significant portion of diabetics who are older, obese, or have cardiovascular disease may not be able to achieve these goals, the authors note.

Hence, there are some important messages for clinicians when discussing exercise with their type 2 diabetic patients, say the researchers.

One is not to give up on exercise — even if treadmill tests aren't showing results — because metabolic measures may tell a different story, and the benefits of exercise likely extend beyond running faster or longer.

And it follows that a less intense regimen may still get results, so modifying the intensity of exercise may be a good trade-off if patients are able to make improvements in metabolic parameters, Dr Pandey said.

"Any exercise would be beneficial…as long as they are [seeing improvements] in other parameters like glucose control, losing weight, and decreasing their waist size," he commented.

Waist Circumference, HbA1c and Body Fat Improve Regardless of Cardiorespiratory Fitness

Dr Pandey and colleagues studied 202 sedentary type 2 diabetes patients (mean age 57.1 years, 63% women) who participated in the Health Benefits of Aerobic and Resistance Training in Individuals With Type 2 Diabetes (HART-D) trial.

They were randomized for 9 months to one of four groups: an aerobic-exercise group; a resistance-training group; a combined aerobic-exercise and resistance-training group; and a control group that did not exercise.

People in all the exercise groups improved their waist circumference, body fat percentage, and HbA1c levels, compared with the control group that did not exercise, regardless of whether they improved cardiorespiratory fitness or not, the researchers found.

The results therefore suggest that exercise-training programs should target metabolic parameters — and assess these for improvement — in individuals with type 2 diabetes, they note.

Physicians may also find such metabolic measures more accurate and somewhat easier to assess — requiring only lab tests, together with a tape measure and a scale — than the complexity of comparing performances on a treadmill, Dr Pandey concluded.

The study was supported by the National Institutes of Health. Dr Pandey reports no relevant financial relationships. Disclosures for the coauthors are listed in the article.

Diabetes Care. Published online June 17, 2015. Abstract

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