December 14, 2009 - By Jennifer Welsh
Adults may stave off weight gain by simply spending less time watching television, according to a new study led by a researcher now at the Stanford University School of Medicine. Overweight adults who cut television time in half were more active, burning more calories as a result.
“Taking away time spent in front of the television has the potential to improve a person’s activity levels,” said Jennifer Otten, PhD, postdoctoral scholar at the Stanford Prevention Research Center and lead author of the study, conducted at the University of Vermont.
The study, published in the Dec. 14 Archives of Internal Medicine, determined how reduced television watching affected calories eaten, energy used, body weight, time spent sleeping and the balance between calorie ingestion and activity in obese and overweight adults.
On average, American adults watch five hours of television a day, the third most time-consuming activity in our lives — after sleep and work. Watching television expends fewer calories than other leisure activities that take its place, including reading, writing, telephone conversations and desk work. The more time adults spend in front of the television, the more likely they are to suffer from obesity, diabetes and cardiovascular disease, said Otten.
The study followed 36 adults, weighing in above the healthy range, who watched an average of five hours of television daily. After three observation weeks, half of the participants were limited to 50 percent less television for three additional weeks, using monitors that controlled their screen time. For the last week of each three-week period, participants wore activity-monitoring armbands, kept sleep logs and answered phone surveys about their diet.
The group instructed to halve their television did not change their calorie intake but burned 120 more calories a day on average, creating a trend of negative energy balance. “The energy burned is equivalent to walking more than a mile,” said Otten. “We don’t know if these short-term changes will translate, but the results may be similar in a longer term study and could prevent weight gain.”
The results from television reduction studies in children, similar to this one, have comparable effects on energy balance, though it was achieved through different means. With children, short-term study results were consistent with longer studies in which researchers found that instead of activity increasing, children’s food intake decreased and they lost weight. The difference may be because children’s diets are less set in stone, they may be more prone to advertisement-induced cravings or they are generally less inactive, said Otten.
“We’ve known for a decade that reducing children’s television viewing is one of the most effective ways to prevent weight gain, so it is great to finally see a study like this in adults,” said Tom Robinson, MD, MPH, the Irving Schulman Endowed Professor in Child Health at Stanford’s School of Medicine, who was not involved in the study but has conducted TV studies in children. “Dr. Otten and her collaborators have demonstrated that reducing TV viewing has the potential to be as important for controlling adult obesity as it is for children.”
The study was funded by grants from the U.S. Department of Agriculture’s Hatch Funds Act and the National Institutes of Health.
Jennifer Welsh is a science-writing intern in the Office of Communication & Public Affairs.
Stanford Medicine integrates research, medical education and health care at its three institutions - Stanford School of Medicine, Stanford Health Care, and Stanford Children's Health. For more information, please visit the Office of Communications website at http://mednews.stanford.edu.