Adults who used an electronic lock-out system to reduce their television time by half did not change their calorie intake but did expend more energy over a three-week period, according to a report in the December 14/28 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.
The average adult watches almost five hours of television per day, according to background information in the article. Some efforts to prevent and reduce obesity have focused on modifying diet and physical activity, but newer strategies have involved reducing sedentary behaviors such as TV watching. Not only may reducing TV time allow time for more active endeavors, it may also help alleviate chronic sleep deprivation, potentially linked to obesity.
Jennifer J. Otten, Ph.D., R.D., then of the University of Vermont, Burlington, and now of Stanford University School of Medicine, Palo Alto, Calif., and colleagues conducted a randomized controlled trial of 36 adults who had a body mass index between 25 and 50 and reported watching at least three hours of TV per day. Between January and July 2008, all participants underwent a three-week observation period during which their daily TV time was assessed. A group of 20 individuals was then randomly assigned to receive an electronic device that shut off the TV after they had reached a weekly limit of 50 percent of their previously measured TV viewing time. An additional 16 participants served as a control group.
As assessed by an armband measuring physical activity, those with the lock-out systems burned 119 more calories per day during the three-week period. In comparison, the control group burned 95 fewer calories per day during the intervention than during the observation period. Energy balance--the comparison of calories consumed to calories burned--was negative in the intervention group (who consumed 244 calories less than they burned each day) but positive in the control group (who consumed 57 more calories than they burned each day); however, this difference did not reach statistical significance.
"A recent task force report supports small behavior changes as a more sustainable, long-term approach to help address the obesity epidemic," the authors write. "It has been estimated that combined increases in energy expenditure and decreases in energy intake equaling only 100 calories per day could prevent the gradual weight gain observed in most of the population."
Previous research with children has found that screen time reductions reduce calories consumed but do not increase calories burned, producing a similar change in energy balance but through a different mechanism, the authors note. "This suggests that adults may differ from children in how they respond to reductions in sedentary behaviors," they conclude. "To our knowledge, this is the first study to measure the effects of a TV reduction intervention in adults. Reducing TV viewing should be further explored as a method to reduce and prevent obesity in adults."
(Arch Intern Med. 2009;169:2109-2115. Available pre-embargo to the media at www.jamamedia.org.)
Editor's Note: This project was supported in part by USDA Hatch Act Funds and by grants from the National Institutes of Health. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.