You're watching your favorite TV show when a commercial ( 广告 ) break starts. First you see an ad for candy. Then there's one for fast food. Your stomach growls ( 咕咕直叫 ). Suddenly, all you can think about is how much you need a snack ( 小吃 ). If that sounds familiar, you're not alone. Researchers from McMaster University in Canada studied the effects of junk ( 垃圾 ) food ads. The researchers examined the effects of advertising junk food on more than 6,000 kids through TV commercials and other types of media ( 媒体 ). They found that kids made unhealthy food and drink choices as quickly as 30 minutes after seeing the ads. “There is too much unhealthy food advertising out there, “Says Behnam Sadeghirad. He's one of the researchers who led the study. “This is dangerous for younger children.” Food and drink ads are everywhere, from TV to the Internet. Companies want to make sure you know about their products. They spend nearly $1.8 billion a year on food ads aimed at kids, according to a report. The Nielsen Company tracked the number of food ads that kids saw in 2015. It found that kids watched nearly 12 food ads on TV each day. Most of these ads weren't for healthy foods. In fact, on average, kids saw only one ad per week for fruits and vegetables. Instead, most of the ads were for fast food, candy, and sugary drinks. Jennifer Harris, a professor at the University of Connecticut, says this is a big part of the problem. “Unhealthy foods are not things we should be encouraging kids to eat more often,” Harris says. “But unfortunately those are the products being advertised to them the most.” Health experts say it's OK to treat yourself to a cookie once in a while. But what can you do to keep from having an unhealthy snack every time you see an ad for junk food? Harris says it's important to learn to spot the techniques companies use in their ads.“What kids can do is notice what's going on,” says Harris.“Think about, ‘Are these the products that really are good for me?' ”