Although women with a history of gestational diabetes are at exceptionally high risk for type 2 diabetes mellitus, if they keep active and minimize the amount of TV they watch, they may lower this risk, researchers report.
In new research — a large prospective cohort study of women with a history of gestational diabetes — those who met US federal guidelines for physical activity had a 45% lower risk of developing type 2 diabetes, independent of body mass index (BMI) and other major risk factors.
The results indicate that such women "should exercise regularly and try to comply with the US federal guidance of at least 150 minutes/week of moderate-intensity exercise [such as brisk walking] or 75 minutes/week of vigorous exercise, such as jogging," senior author Cuilin Zhang, MD, from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, in Rockville, MD, told Medscape Medical News in an email.
While upping exercise appeared to ward off diabetes in these high-risk women, the opposite habit — sitting transfixed in front of a television — was associated with an increased risk of developing diabetes, largely due to increased BMI.
"TV watching typically acts as a sedentary replacement for physical activity, leading to a reduction in energy expenditure," Dr. Zhang noted. It "is associated with 'mindless' eating, [and viewers] may be influenced by commercial food advertisements for nutrient-poor, high-calorie foods."
The study was published online May 19 in JAMA Internal Medicine, by Wei Bao, MD, PhD, also of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, and colleagues.
High-Risk Women
Gestational diabetes occurs in 4% to 7% of pregnancies and is more common among the obese, minorities, and older women, Dr. Zhang explained. Gestational diabetes increases the risk of developing type 2 diabetes within the next 20 years, although estimates vary widely as to the number of women who will go on to develop full-blown diabetes, ranging from 16% to 60%.
Previously, the same research group reported that women with a history of gestational diabetes who followed a healthy diet had a lower risk of developing type 2 diabetes. But little is known about other risk factors that might affect progression to type 2 diabetes, they explain.
They set out to examine the association between physical activity and TV watching and other sedentary behavior with risk of developing type 2 diabetes.
In the Nurses' Health Study II, 4554 women who had a history of gestational diabetes were identified and followed from 1991 to 2007. At baseline, the women, who were mostly white, had an average age of about 38 and an average BMI of around 27, and about a quarter had a family history of diabetes.
The participants filled in questionnaires in 1991, 1997, 2001, and 2005 in which they reported the average time they spent each week walking, jogging, running, bicycling, doing calisthenics, using a rowing machine, swimming, or playing squash, racquetball, or tennis. From this, the researchers determined the metabolic equivalent (MET) hours per week that were expended in total physical activity, vigorous physical activity, or walking.
The women also reported the average time they spent each week at home watching television, sitting at home doing other things, or sitting at work or driving.
A total of 635 women developed type 2 diabetes.
Each incremental increase of 5 MET/week — or about 100 minutes per week of moderate-intensity physical activity or 50 minutes per week of vigorous-intensity activity — was associated with a 9% lower risk of developing type 2 diabetes.
Both walking and vigorous activity were associated with a similar lower risk of type 2 diabetes mellitus, which is "reassuring," the authors write.
And compared with watching less than 6 hours of television a week, watching 6 to more than 20 hours a week was associated with a 28% to 77% increased risk of developing type 2 diabetes. The risk was lower after adjustment for BMI. Other sedentary behaviors were not linked with risk of type 2 diabetes.
"Hopeful Message," "Call to Action"
"The article by Dr. Bao et al provides evidence of a hopeful message for women with gestational diabetes mellitus, that if they can increase their physical activity, they may potentially reduce or delay their risk of developing [type 2] diabetes," Monique Hedderson, PhD, and Assiamira Ferrara, MD, PhD, of Kaiser Permanente Northern California, in Oakland, California, write in an accompanying editorial.
And the advice to up exercise applies to all young women, they stress. "Clinicians should recommend a comprehensive lifestyle approach, including healthful diet and increasing physical activity for all women, especially those who are planning to become pregnant, in an effort to prevent obesity, gestational diabetes, and diabetes," they note.
"Considering the urgency of addressing the current diabetes and obesity epidemics, [the] article is also a call to action for researchers and health systems to develop successful interventions to increase physical activity among women of reproductive age," they conclude.
The authors and editorialists have reported no relevant financial relationships.
JAMA Intern Med. Published online May 19, 2014. Abstract Editorial
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Cite this: Less TV, More Exercise Wards off Diabetes After Pregnancy - Medscape - May 21, 2014.
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