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

To address the epidemic of type 2 diabetes, researchers suggest that physicians must now target a new risk factor — physical activity deficiency — that can significantly increase a person’s likelihood for developing the disease.

In a study published in Diabetologia, researchers found that each hour of sedentary time may be associated with a 22% increased risk for developing type 2 diabetes. Interestingly, the study also showed that sedentary behavior may play a significant role in the development and prevention of type 2 diabetes, independent of high-intensity physical activity.¹

“We know that exercise is important in the prevention and management of type 2 diabetes,” said lead study investigator Julianne van der Berg, a PhD candidate in Social Medicine at Maastricht University in the Netherlands. “In our study, we aimed to investigate the association between sedentary behavior and type 2 diabetes in a large population-based study in the Netherlands: The Maastricht Study.”

Previous observational studies have found associations between patterns of sedentary behavior and metabolic health, she explained, but the findings have been inconsistent. As a result, van der Berg and colleagues wanted to further examine this issue.

Sedentary Behavior Linked to Type 2 Diabetes Risk

The researchers investigated cross-sectional associations of total amount and patterns of sedentary behavior with glucose metabolism status and metabolic syndrome. The study included 2497 participants (mean age, 60 years; 52% men) who were asked to wear an activPAL accelerometer for 24 hours a day for 8 consecutive days. 

The researchers then calculated the daily amount of sedentary time and the daily number of sedentary breaks. They also calculated prolonged sedentary bouts of 30 minutes or longer and the average duration of the sedentary bouts.

All participants underwent an oral glucose tolerance test to determine their glucose metabolism status.

Multinomial logistic regression analyses were used to evaluate the associations of sedentary behavior variables with glucose metabolism status and metabolic syndrome.

Results revealed that 55.9% of the participants (n=1395) had normal glucose metabolism; 15.5% (n=388) had impaired glucose metabolism; and 28.6% (n=714) had type 2 diabetes. The odds ratio for each additional hour of sedentary time was 1.22 for type 2 diabetes and 1.39 for metabolic syndrome.¹

“Our study is the largest in which a physical activity monitor (accelerometer) was used to objectively measure total amount and patterns of sedentary behavior in a sample of adults comprising participants with type 2 diabetes,” van der Berg told Endocrinology Advisor. “We showed that participants with type 2 diabetes spent the most time per day being sedentary, 26 minutes more than participants without diabetes.”

These new findings could have important public health implications, according to van der Berg. Adopting strategies to reduce the amount of sedentary time in diabetes prevention programs could be highly beneficial. 

“Promotion of physical activity (exercise) and reducing daily sitting time may be beneficial for health,” said van der Berg. “Future studies should be conducted to confirm our results and also dose-response relationships, as well as and long-term effects of prolonged sitting should be examined.”

Growing Evidence on Importance of Exercise

Similarly, another study has shown that sedentary behavior may be associated with poor cardiovascular health and type 2 diabetes in adults with severe obesity, independent of how much they exercise.² The findings, which were recently published in Preventive Medicine, suggest that replacing sedentary behavior, such as watching television or sitting at the computer, with low-intensity physical activities could improve cardiometabolic health in this patient population.

For this study, researchers followed 927 patients participating in the Longitudinal Assessment of Bariatric Surgery-2, a prospective study of patients undergoing weight loss surgery at 1 of 10 different hospitals across the United States. For a 1-week period before surgery, the researchers measured the participants’ activity using monitors that tracked the number of steps taken each minute.

They found that for every hour per day participants spent in sedentary bouts of at least 10 minutes, the odds of having diabetes increased by 15% and the odds of having metabolic syndrome increased by 12%.² This study suggested that sedentary behavior may be a distinct health risk behavior among adults with severe obesity.

Marc Hamilton, PhD, director of Texas Obesity Research Center and professor at the University of Houston-Central, said the study conducted by van der Berg and colleagues is important because the researchers found, using accelerometers, that the amount of time a person is inactive each hour of the day is significantly related to both diabetes and metabolic syndrome. However, the odds of 22% and 39% for each hour of daily sedentary time are very high, he noted. 

“We must put [the results] in perspective with the fact that the average person sits about 10 hours per day. The numbers from my laboratory reported previously agree with these numbers, and we described that there is typically a 4.5 hour per day range in sitting time within each week for most all individuals as well as between quartiles in the population,” Dr Hamilton told Endocrinology Advisor. 

“The major conclusion to all of this is that although inactivity physiology is still a relatively new science, there are now many new studies showing that the risks of sitting inactive for developing diabetes are actually markedly greater than whether or not one engages in the longstanding lifestyle recommendations of traditional moderate to vigorous exercise.”