Physical Activity Deficiency: A New Risk Factor for Type 2 Diabetes?

Maastricht Study: How Informative Are the Results?

Among people who already have type 2 diabetes, exercise can trim waist size and body fat, and control blood glucose, results of a study published in Diabetes Care suggest.3

In this study, investigators found that waist circumference, percentage of body fat, and HbA1c levels all were improved in patients with diabetes who exercised compared with those who did not exercise. In addition, the beneficial effects of exercise were seen whether they participated in aerobics, resistance training, or a combination of both types of exercise compared with a control group that did not exercise.

Robert Eckel, MD, professor of medicine in the division of endocrinology, metabolism, and diabetes at the University of Colorado Anschutz Medical Campus Director Lipid Clinic in Denver, noted there is now enough evidence to change the conversations clinicians have with patients.

The message needs to be that sedentary behaviors are a significant risk factor for type 2 diabetes as well as other metabolic disorders, said Dr Eckel, who is also a spokesperson for the American Heart Association.

“The Dutch study adds to the more recent evidence that it’s not just exercise but the absence of sedentary behavior in diabetes and metabolic conditions that relate to diabetes risk, such as prediabetes and metabolic syndrome,” Dr Eckel told Endocrinology Advisor. “I’m not surprised by the percentage of 22% and feel that this is a major message organizations like the ADA (American Diabetes Association) need to promote. Let’s get off our duffs and reduce the incidence and prevalence of type 2 diabetes and related disorders such as cardiovascular disease.”

On the other hand, the study conducted by van der Berg and colleagues is cross-sectional and compares the activity or exercise patterns of patients who have normal glucose status, impaired glucose status, or diabetes, noted Ildiko Lingvay, MD, an associate professor of internal medicine at the University of Texas Southwestern Medical Center in Dallas.

Therefore, while it may be an important and very interesting study, the results cannot directly inform clinicians about prevention of diabetes through exercise or physical activity, according to Dr Lingvay.

“Other studies, though, have clearly shown that exercise/physical activity can prevent diabetes, but this was not the purpose of this study. A cross-sectional study can only show an association, but not causality,” Dr Lingvay told Endocrinology Advisor.

Samuel Klein, MD, professor of medicine and nutritional science and director of the Center for Human Nutrition at Washington University School of Medicine in St. Louis, Missouri, agrees with Dr Lingvay.  However, he said clinicians have relied on cross-sectional studies when evaluating other risk factors.

“This type of study cannot show cause and effect, but it is just like smoking. Lung cancer was linked to smoking in a study just like this one,” Dr Klein said in an interview with Endocrinology Advisor. “So, you can make decisions based on this type of study and in the context we know there is very strong evidence about cause and relationship even though it is this type of study. You can’t exclude the possibility that the patients with diabetes are sicker and can’t exercise as much, but these data make sense.”

In addition, these data are important because the study used an accelerometer to measure how often participants were sedentary, and it included such a large number of patients, according to Dr Klein. He also said the study was very well designed and highlights the effects of physical activity deficiency. 

“This is a real problem and clinicians have to address this. Type 2 diabetes is related to a physical inactivity deficiency and it does lead to insulin resistance and metabolic syndrome,” said Dr Klein. He believes that physical activity deficiency is a term that now should be adopted and guidelines should be established that address it.

References

  1. van der Berg JD, Stehouwer CDA, Bosma H, et al. Associations of total amount and patterns of sedentary behaviour with type2 diabetes and the metabolic syndrome: The Maastricht Study. Diabetologia. 2016;59(4):709-718. doi:10.1007/s00125-015-3861.
  2. King WC, Chen J-Y, Courcoulas AP, et al. Objectively-measured sedentary time and cardiometabolic health in adults with severe obesity. Prev Med. 2016;84:12-18. doi:10.1016/j.ypmed.2015.12.007.
  3. Pandey A, Swift DL, McGuire DK, et al. Metabolic Effects of Exercise Training Among Fitness Nonresponsive Patients With Type 2 Diabetes Mellitus: The HART-D Study. Diabetes Care. 2015;38:1494-1501. doi:10.2337/dc14-2378.