New research suggests that the amount of time adults spend watching television each day could predict whether or not they will become obese.

Researchers at the University of Pittsburgh found that the more hours young adults spend watching television each day, the greater the likelihood that they'll have a higher body mass index and bigger waist circumference.

"We were quite surprised to find that television viewing was associated with subsequent obesity for young adults, but not for the middle-aged," Anthony Fabio, lead author of the study, said in a statement. "This suggests that middle-aged adults may differ from young adults in how they respond to the influence of TV viewing."

For the 15-year study, researchers collected and analyzed data from more than 3,000 adults  from Birmingham, Ala., Chicago, Minneapolis, and Oakland, Calif. Starting in 1990, study participants reported their television viewing habits and had their waist circumference measured and their body mass index calculated every five years.

Researchers found that people who spent more time watching television when they were approximately  30 years old  were more likely to be obese five years later, compared to their peers who spent less time in front of the television.

They also found that a lower family income and higher rates of smoking and drinking were also associated with more time spent watching television.

"Television viewing and obesity are both highly prevalent in many populations around the world," Dr. Fabio said. "This means that even small reductions in television viewing could lead to vast public health improvements. Reducing sedentary time should be a healthy lifestyle guideline heavily promoted to the public. Our study indicates that the biggest bang for the buck would be in targeting young adults for interventions to reduce television viewing. Healthy lifestyle behaviors should start at early ages."

The findings are detailed in the SAGE Open.