A new study to be published next month in the American Journal of Preventive Medicine shows that while we watch about the same amount of TV all the time, on days that we exercise we tend to back off from light activities like household chores and shopping trips, probably without even realizing it. Moving around less in those ways, combined with the time we typically binge-watch Netflix, adds up to negating about half the benefit of a moderate-intensity, 60-minute workout — which could explain why you're not seeing the results you expected when you committed to fitting in exercise three days a week.
Researchers at the National Cancer Institute arrived at this result — call it your energy set point, exercise compensation factor, or workout sabotage — using very detailed time-use surveys collected in conjunction with AARP. Those surveys required middle-aged participants to painstakingly record, via periodic questionnaires throughout the year, how they spent particular workdays and weekend days, down to the minute.
The study authors then calculated energy expenditure based on the reported activities adjusted for things like participants’ age and gender, season of the year, and day of the week.
Along with noting how TV viewing time rarely budged and that most men and women were overall sedentary for about nine or 10 waking hours a day, researchers found that workdays correlated with the most TV watching at night, as well as less sleep.
Overall, the study authors noted that their findings “provide new insights into possible compensation associated with exercise, and suggest a strong link between TV viewing and physical inactivity.” To anyone hoping to see results with their workouts, the study suggests that counting your total daily steps with something like a Fitbit could be valuable, as could simply going screen free a few nights a week.