This week, Fox outlined its big promise to advertisers ahead of the upcoming TV season: less will really be more.

Fox Networks Group -— the division of 21st Century Fox (FOXA) that controls the company's broadcast, cable and sports channels — says it will shorten commercial breaks during some of its programs to one minute, or two 30-second spots back to back.

Viewers will notice the difference during some live sports events (Fox isn't saying which ones) and on cable channels, including FX. Some Sunday nights on the Fox broadcast network will also feature the new format, so you might catch the change if you're a fan of "The Simpsons," for example.

The announcement, which came Monday during Fox's Upfront presentation to advertisers, was one example of how traditional TV networks are trying to compete in an era of cord cutting and declining viewership.

NBCUniversal announced a similar move toward fewer ads in March. TNT and TruTV have also already made such cutbacks. (Their parent company, Time Warner (TWX), also owns CNN.)

Related: Why you'll see fewer ads on NBC this fall

"Clutter on an industry level is a big problem, and there's not a good way out of it," said Brian Wieser, a senior advertising analyst at Pivotal Research Group. "Everyone's had to get creative."

Not every show on Fox or NBC is getting the new treatment -— and for good reason. Wieser said that both networks can charge more for the new commercial spots, since there won't be as many available. He expected that only a handful of advertisers would be willing to pay the premium.

But Wieser added that selling marketers on fewer ads is a good story to start telling now, especially if the networks are going to keep moving in that direction.

"They certainly need a story about de-cluttering," he said. "You hope to get a good case study or two that you'll then talk about, and you'll persuade more people to do it."

The trend isn't for everyone. During CBS' (CBS) ad presentation Wednesday, president and chief advertising revenue officer Jo Ann Ross took a dig at Fox and NBC.

"Unlike those who are focused on commercial loads, we do not believe that advertising is ruining the television business," she said.

Wieser said CBS's strategy has merit. The broadcast network is the company's most important asset. Advertisers have plenty of reason to flock to broadcast channels, since they have far wider reach than anything locked behind a cable bundle.

Fox and NBC also have broadcast networks, but they have far more cable channels than CBS. Wieser noted that CBS's strategy could change should it merge with Viacom (VIA), since the latter has more cable channels than CBS.

Related: CBS crisis comes to a head as Moonves and Redstone fight for network's future

In any case, traditional TV networks need to find ways to keep advertisers coming back. Magna, a company that monitors audience trends, predicts that national TV ad sales will decline about 2 or 3% over the next few years.

David Cohen, the North American president of Magna, said he expects networks to keep tinkering with ads as they search for what advertisers are willing to pay for, and what audiences are willing to stomach.

For example, networks have recently debuted the six-second commercial and the "double box," which is when a program and an ad are broadcast side-by-side. Several networks also talked this week about how they're using data to help advertisers target viewers.

"We are all besieged by thousands of advertising and marketing messages a day," Cohen said, adding that advertisers need to figure out how to break through.