If you want to burn more calories, scientists have a not-so-surprising solution: switch off the TV.
A new study, based on a small sample, finds that while adults who reduce their television watching still eat about the same calorie-wise, they expend more energy than those who don't cut back on tube-time.
The average adult watches almost five hours of TV per day, the authors say. 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 could reducing stints in front of the tube allow time for more active endeavors, it may also help alleviate chronic sleep deprivation, potentially linked to obesity.
To investigate the impact of less TV, the researchers monitored daily TV time for 36 adults who reported watching at least three hours of TV per day and had a body mass index (BMI) between 25 and 50. BMI is an approximation of how much body fat a person has based on height and weight. A person with a BMI over 30 is considered obese.
Then during another three-week stint, a randomly chosen group of 20 of the participants received 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. The remaining 16 participants served as a control group. An armband device measured all participants' physical activity.
Those with the lock-out systems burned 119 more calories per day during the three-week period than during the observation period. In comparison, the control group burned 95 fewer calories per day.
The group also burned more calories than they consumed. On the other hand, the control group ate slightly more calories than they burned, although the researchers note that this finding was not statistically significant, meaning it could be due to chance.
While the calorie differences may seem small, they could have an effect on weight over time, the researchers say. "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," the researchers write in their report, published in the Dec. 14 issue of the Archives of Internal Medicine, a journal of the American Medical Association.
Small changes in behavior may be a more sustainable approach to address the obesity epidemic, they add.
Previous research with children has found that less screen time reduces 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.
Watching TV has also been linked to other negative consequences, such as unhappiness and learning lags in infants.
The current study was conducted by Jennifer J. Otten, then of the University of Vermont, Burlington, and now of Stanford University School of Medicine, Palo Alto, Calif., and her colleagues.