Aug. 1, 2013  -- They say, "No pain, no gain," but a new weight-loss method turns that old saying on its head.

Marlene Beltran weighed 169 pounds because, she told ABC News' Cecilia Vega, of her out-of-control appetite.

"I'm willing to do anything at this point," Beltran said. "I'm so desperate to lose the weight."

Watch the full story, including Lanuza and Beltran's video diaries, on "Nightline" TONIGHT at 12:35 a.m. ET.

Lysander Lanuza was 200 pounds of all-you-can-eat.

"I love eating everything," she said. "American food, Filipino food, Korean. ... It's heaven."

These two women were about to have a hard plastic mesh sewn onto their tongues that would inflict pain if they tried to eat any solid food. Their goal was to lose 20 pounds in one month. Beltran wanted to begin dating. Lanuza had a bikini and a trip to Hawaii planned.

Cosmetic surgeon Dr. Nikolas Chugay, of Long Beach, Calif., introduced the procedure in the U.S. four years ago after seeing it in Latin America.

Chugay said Lanuza was his 81st patient. One clinic in Caracas, Venezuela, said it had stitched patches on more than 800 tongues.

Asked if sewing a foreign object into somebody's mouth was healthy, Chugay said, "Well, it's not unhealthy."

"It's a pattern interrupt," he said. "When patients want to swallow food, they realize, 'Hey, I cannot do that. That's why I have this patch here.'"

Patients go on a strict, 800-calorie-per-day liquid diet of shakes and low-calorie beverages until the patch is removed after one month. The plan also involves a 45-minute daily workout.

"An average weight loss is anywhere from 18 to 20 pounds," Chugay said.

The ten-minute procedure costs $2,000 and takes 10 minutes.

Lanuza paid full price, but Dr. Chugay did Beltran's procedure free, because ABC News recorded it for its report.

Chugay said he has not received flak from the medical community. That may change.

"I think it's ridiculous," said Dr. Christine Petti, a plastic surgeon in nearby Torrance, Calif. "I could never advise a procedure that would cause a patient pain. ... Pain is not a good thing for anybody."

"I think it's a barbaric procedure," said Dr. Rob Huizenga, a specialist in long-term weight-loss who spent 14 seasons as an expert on "The Biggest Loser."

"This is so primitive an approach," Huizenga said. "You could hire somebody to hold a gun to your head and threaten to shoot you every time you eat. You could have somebody with a hammer hit you over the head every time you threaten to have something to eat."

Asked if he would use a tongue patch on himself, Chugay said he would.

Family members?

"Well, so far I have no volunteers," he said, laughing.

On day five, Beltran had an acute craving: In-N-Out Burger.

"I don't care if it's a bite," she said. "I just want a burger."

She resisted.

Lanuza's first craving came at the movies.

"I tried, like, a piece of popcorn," she said. "And it hurt. So, I'm like, forget it!"

Chugay said the tongue patch can jump-start lasting weight loss.

"It takes about 30 days to change a habit," he said. "That's what we are doing. We are helping people to change habits."

"If I could say one thing, it's that the whole concept that you jump-start is absurd," Huizenga said.

Studies show most extreme dieters who lose weight rapidly eventually gain it all back -- and more, he said.

"There's not one scintilla of hope or evidence that putting a patch on your tongue and not being able to eat for a month is going to have any effect on you at one year, or two years or three years," he said.

Chugay's son and partner, Dr. Paul Chugay, submitted to the American Journal of Cosmetic Surgery a study claiming that 70 percent of their patients lost an average of 16 pounds and kept it off for eight months.

The journal refused to publish it without more data.

On day 8, Beltran said, "My double chin is not as bad as it used to be. My arms are thinner. My stomach is not as flabby."

By day 20, Lanuza had lost 15 pounds.

On day 22, Beltran said, "I'm getting a lot of attention from guys. It's attention I'm not used to, so it's nice."

The final tally: Beltran lost 18 pounds, Lanuza 23.

"Once they take the patch off, we put them on the boot camp diet," Dr. Nikolai Chugay said. "It's a strict diet, kind of plant-based diet that patients are placed on for another month. And then, I prepare them for the regular maintenance diet that they'll stay on for the rest of their lives."

Or not. Within hours of having the tongue patch removed, Lanuza enjoyed her favorite feast: Korean barbecue.

Beltran cracked after three days, having a slice of cake and two tacos.

She said she has no regrets about getting the tongue patch.

"It was great," said Beltran -- who, remember, had the procedure done for free. "It wasn't hard for me to do it. And I found the shakes really good."

Lanuza felt differently.

"I don't want to go through that again," she said. "It was really hard for me."

"It is really an extreme way to lose weight," Lanuza added.

Is it crazy?

"Yes, I think it is," she said. "I mean, comparable to the other diets that I know, yes."

Watch the full story, including Lanuza and Beltran's video diaries, on "Nightline" TONIGHT at 12:35 a.m. ET.