Artificial sweeteners are on the outs with consumers, as evidenced by a drop in sales of Splenda, Equal and Sweet'N Low and share declines among diet-soda brands. Now, Truvia, a natural sweetener made from the stevia plant, is looking to press its advantage with a series of spots going directly after its sugar-substitute rivals.

Consumers' backlash against artificial sweeteners has led food and beverage giants such as PepsiCo, Coca-Cola, Smuckers, Kraft and Pernod Ricard to introduce products that use stevia, raising the ingredient's profile (a cameo in the series finale of "Breaking Bad" didn't hurt, either).

"Being natural is key for consumers," said Bill Pecoriello, CEO at Consumer Edge Research. "They are increasingly trying to avoid artificial sweeteners."

According to IRI, between 2009 and 2012, sales of Splenda fell 26%, while Equal declined 17% and Sweet'N Low dropped 15%. Meanwhile, sales of Truvia, introduced in 2008, have nearly tripled. Sugar substitutes are a $750 million market, according to Truvia.

Splenda and Equal did not respond to requests for comment. Monica Oliva, Sweet'N Low brand manager, said that while the artificial-sweetener category has been declining, consumer loyalty remains strong, and she claims that Sweet'N Low has maintained "more of its market share than its competitors." She noted the brand recently launched a campaign, "The Sweeter The Better."

Truvia, meanwhile, sees an opportunity to shake up consumer habits. Since its launch, the brand has been focused on consumer education, spending between $25 million and $40 million annually on measured media, according to Kantar Media. In its "Sweet Switch" campaign, created by Seattle's Creature, yellow, blue and pink sweetener packages are thwarted by Truvia.

"The category is low-involvement. When you go to the condiment bar in a coffee shop or even a break room, you're not thinking about those choices. You're not making a deliberate choice," said Mark Brooks, global business director for Truvia's consumer-products division. "We need to disrupt that thought pattern ... and realize there is this other choice."

As part of the campaign, Truvia is offering consumers a money-back guarantee. "This campaign builds on what we've done, but also builds on trends around health and wellness," Mr. Brooks said. "People are starting to ask questions about what's in the food they're consuming."