People with diabetes who exercised regularly but didn’t increase their fitness levels still managed to improve their blood sugar and other important health factors, according to new research published Wednesday in Diabetes Care.

Researchers enrolled 202 people with Type 2 diabetes into three exercise groups and a control group. Exercisers did aerobic conditioning, resistance training or a combination of the two for nine months.

People in all the exercise groups improved their waist circumference, body fat percentage, and hemoglobin A1c levels, regardless of changes to fitness capacity, according to researchers. Hemoglobin A1c is a long-term measure of blood sugar.

“What this study does is go against a hypothesis that cardiorespiratory fitness is everything,” said Robert Eckel, M.D., former American Heart Association president and professor of medicine at the University of Colorado Anschutz Medical Campus, who was not involved in the study.

Health improvements may be more important to measure than fitness levels, which could simplify things for physicians, Eckel said.

For many people, exercising regularly improves fitness levels, measured by how well the body exchanges carbon dioxide and oxygen. However, 30 percent of people don’t improve despite exercise, Ambarish Pandey, M.D., the study’s first author and a cardiology fellow at UT Southwestern in Dallas said in a written statement. They’re known as “non-responders.”

“This finding suggests that our definition of ‘non-responder’ is too narrow. We need to broaden our understanding of what it means to respond to exercise training,” wrote Jarett Berry, M.D., co-senior author of the study and associate professor of Internal Medicine and Clinical Sciences at UT Southwestern.

Diabetes is a major risk factor for heart disease and stroke, and more than 21 million adults in the U.S. have been diagnosed with diabetes, according to the 2009–2012 National Health and Nutrition Examination Survey.

Eckel said the study reinforces the need for medical professionals to encourage diabetes patients to be more active, to help them lose body fat and improve their diabetes control.