By JEANNETTE NEUMANN

On Saturday, pork aficionados will meet up in Des Moines, Iowa, for the fifth annual Blue Ribbon Bacon Festival, billed as America's "premier" bacon celebration.

The event, which sold out all 4,000 tickets in 25 minutes, offers something to make every swine lover swoon: unlimited bacon samples, a bacon-eating contest, educational lectures, a bacon-themed songwriting contest and crowning of a new bacon queen. Organizers plan to serve up about three tons of the fatty strips.

They're also prepared for a bit of oinking from outsiders.

A group of vegetarian doctors has been skewering Iowans over the event for months. Neal Barnard, president of the Physicians Committee for Responsible Medicine, says he wants to publicize the flip side of bacon.

He says the PCRM plans to hand out fliers with warnings about how bacon "rotting in your mouth" potentially has various health risks, including cancer and diabetes.

"With so much attention focused on this most unhealthful food, we want to make sure our message is there," says Dr. Barnard.

The group had already sizzled up trouble in advance of the event, starting with a billboard that made graphic reference—with skull and crossbones—to the potential health risks of eating bacon.

PCRM doesn't limit itself to bacon-bashing: It also has taunted cheeseheads with a billboard near the Green Bay Packers' football stadium and hot-dog lovers at a Nascar race in Indianapolis.

Still, the anti-bacon campaign is proving to be an uphill battle. After canvassing the state, the doctors' group has so far enlisted only six volunteers, and has been locked out of the event's official schedule.

As the festival loomed, organizers tried to serve up a sort of detente. They invited the doctors' group to participate in a lecture series where festival attendees would have the chance to heighten "their bacon knowledge and beliefs."

Susan Levin, the PCRM's nutrition-education director, says the offer came with impossible strings attached: She had to agree to discuss how bacon fits into a healthy diet.

"Of course, I said no," she says.

Pro-bacon lecturers at the festival will speak about "Zombies, Bacon and Survival" and "How Bacon Is Changing My Life."

Late last week, Ms. Levin sent one last email appeal, asking to speak on her own terms. But organizers say attendees don't want to be bummed out. Her request was denied.

The doctors group's ultimate goal is to raise awareness of the benefits of a plant-based diet. Those who crave bacon's taste but want to avoid "the embarrassment" associated with the meat and its potential health effects, says Dr. Barnard, can enjoy bacon-like strips made from soy.

Brooks Reynolds, who helped start the Blue Ribbon Bacon Festival in 2008 and signs his emails with "OHHHH, BACON!" says organizers don't see the need to serve turkey bacon, let alone the fake stuff.

"Who doesn't love bacon?" he says. "Even vegetarians will come back."

Elizabeth Cummings, a 41-year-old Iowa City vegan who plans to hand out leaflets Saturday, says she was shocked when her health-food cooperative in Iowa City hosted cooking classes last year called "We Love Bacon."

The doctors' group set its sights on Iowa because it is smack in the heart of bacon country, with about six times as many pigs as people. Last year, the Iowa House of Representatives declared Feb. 26 Iowa Bacon Day.

"Whereas, the people of Maine have lobster, the people of Idaho grow great potatoes, and the folks of Texas make great chili, we Iowans have bacon—nature's perfect food," the resolution declared.

On Wednesday evening, Iowa Gov. Terry E. Branstad served Chinese Vice President Xi Jinping a "Taste of Iowa" meal. The canapés and main course included bacon and the first course featured prosciutto, a dry-cured ham. Mr. Xi, on a U.S. tour, is expected to become China's top leader later this year.

Growing up in Fargo, N.D., even Dr. Barnard chowed down on bacon.

Both his father and grandfather were cattle ranchers. His palate changed, though, when he went off to Washington, D.C., for medical school.

A pathologist told Dr. Barnard, then 22 years old, to unlock a morgue freezer, pull out a body and help him examine the patient, dead from a heart attack.

The patient's arteries were "hard as a rock," Dr. Barnard recalls. The pathologist replied: "There's your bacon and eggs, Neal."

Soon, the medical student began to leave his carnivorous ways behind.

While bacon now disgusts Dr. Barnard, Mr. Reynolds's passion for the meat has swelled to a point where "people basically talk to me about bacon all the time," Mr. Reynolds says.

Corinne Joshu, an expert on colorectal cancer at Johns Hopkins University, says that while a high intake of processed meats like bacon and hot dogs have been "consistently associated with an increased risk of colorectal cancer," moderation is the key. Dr. Joshu says even she "likes a little bacon now and then."

The annual bacon festival has its origins in an annual weekend gathering of Mr. Reynolds and more than a dozen friends at a lakeside cabin in Iowa. They often sat around a campfire and professed their love for bacon.

"I love bacon," he says. "Bacon loves me."

The event has morphed into one of the hottest tickets in Des Moines. This year's installment, the fifth annual festival, is dubbed "Baconpocolypse Now: I Love the Smell of Bacon in the Morning."

Dr. Barnard believes that the group's billboard grabbed the attention of some drivers, prompting awareness of the meat's potential health risks.

Some passersby had a different reaction. Coleman Young, a 36-year-old computer programmer, says the sign made him want to turn his car around, go home and fry bacon.

Tom Halterman, a health-care executive, agreed the billboard was tantalizing—but ultimately ineffective. "I don't see it taking a bunch of Midwesterners who have eaten bacon all their life and turning them to a vegan diet," says Mr. Halterman.

Write to Jeannette Neumann at jeannette.neumann@wsj.com