As previously recommended by the AAP, babies or toddlers younger than 2 years should avoid all screen media. Parents need to limit their children to 1 to 2 hours of screen time per day, and remove TVs, Internet connections, and video games from the child’s bedroom. Children with a TV set in their bedroom increase their risk of obesity by 31 percent, watch more PG-13 and R-rated movies, and double their risk of smoking.

这主要时整天看电视不运动容易胖，还有就是看了电视或网上不该看的东西影响行为。所以控制screen media内容、限制screen media时间、多活动就行了。