Panera Bread is ready to shout a 100% clean food message after more than two years of work to eliminate artificial items found in everything from salads to sweets.

In 2014, Panera said it would remove artificial flavors, sweeteners, preservatives and colors from artificial sources from all of its foods in its restaurants and in grocery stores by the end of 2016. Now that it has met its self-imposed deadline, on Jan. 9 it will begin declaring "100% of our food is 100% clean" through marketing including a TV commercial, billboards and T-shirts worn by staff at its roughly 2,000 outlets. The push follows the overarching "Food as it Should Be" campaign that began in 2015 and still uses that tagline.

"We think simpler, cleaner, real ingredients, the type of ingredients you find in your own pantry taste better and are better for you," Chris Hollander, senior VP and head of marketing. "Why complicate food if it doesn't need to be?"

The new campaign includes a TV spot (above) that shows "mystery meat" and coloring derived from test tubes before explaining the clean overhaul Panera has made. It comes as more restaurants are trying to attract diners looking for food they feel better about eating, whether that be free from artificial ingredients, less processed, fresh, or whatever they might consider healthy. McDonald's cleaned up items including its Chicken McNuggets last year as it tries to have people feel better about visiting its thousands of restaurants. And this week, Chipotle Mexican Grill promoted a new online page to help people looking for foods that meet certain dietary restrictions.

After Panera cleaned up its soups, salads and sandwiches, in late 2016 it was busy eliminating artificial ingredients from its baked goods. Now, even the new Kitchen Sink cookie loaded with chocolate, caramel and pretzels is considered "clean." Still, that one is not necessarily the most diet-friendly treat and is meant to be shared, with 800 calories and 43 grams of fat. Other new treats are a bit less indulgent, such as a new coconut macaroon with 140 calories and 7 grams of fat.

Panera's "100% clean" marketing is set to run through the end of the first quarter, with clean still serving as a key message beyond that time, Mr. Hollander said.

Along with TV commercials and other traditional advertising, Panera has been interacting more directly with fans, who while not paid influencers do get to sample new items, Mr. Hollander said, and often share posts on social media.

"We'll be shifting more and more toward digital and mobile, but TV will still play a significant role for us," Mr. Hollander said.

Panera works with Anomaly as its main creative agency and social media lead; Willoughby on in-store materials; Maxus on media; and Sloane and Weber Shandwick on public relations.

Panera's measured media spending was $51.4 million through the first nine months of 2016, according to Kantar, while the chain's total annual media spending is about $100 million, according to the company. Panera's third-quarter revenue rose 3%, with systemwide sales at longstanding locations up 1.7%.