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The FDA has approved a new weight loss aid that expands in your stomach to help you feel full with less food. Getty Images

The Food and Drug Administration (FDA) issued a rare approval for a new weight loss device this week.

Plenity, created by Boston biotech company Gelesis, is a hydrogel capsule made with a proprietary blend of cellulose (a type of fiber) and citric acid.

In a first from the FDA, Plenity has been approved for use in people with a body mass index (BMI) of 25 to 40. This includes people in the overweight and obese BMI categories.

Most previously approved devices were for people only with a BMI above 30, or those in the obese category.

People below that threshold weren’t approved to use previous weight loss drugs unless they had a preexisting medical condition, such as heart disease or sleep apnea.

The FDA, in their sweeping approval of Plenity, cautions that it must be used alongside diet and exercise. It may also be used with other weight loss medications.

Plenity is taken as a three-capsule dose 20 to 30 minutes before you sit down for lunch or dinner.

Inside each capsule the two ingredients form a three-dimensional hydrogel matrix. Once in the stomach, the capsules break apart, exposing the matrix to water. Each of the hydrogel cells can absorb up to 100 times its weight, growing in size to occupy space in the stomach and intestines.

The result is that you feel full and have less room for food, thus you’re likely to eat less.

After you eat, the hydrogel matrix moves out of the stomach, where it breaks down in the intestines. The cells release the water they absorbed back into your gastrointestinal (GI) tract, then exit the body during a bowel movement.

Because the body doesn’t absorb the hydrogel — it passes through the gut and out the end of the GI tract — the FDA considers it to be a “device,” not a drug.

“Much like taking psyllium mixed with water to create a fiber-rich drink to keep you fuller longer, this new product appears to work the same way,” said Julie Upton, MS, RD, co-founder of Appetite for Health.

“The key to fiber supplements is to drink extra water, which by the way can help with weight loss,” she said.

The FDA greatly relied on the results of a 2018 study in the journal Obesity to give the thumbs up for Plenity.

The Gelesis Loss of Weight (GLOW) study, which was paid for by Gelesis, recruited 436 adults with a BMI between 27 and 40.

For 24 weeks (six months), participants were given either a placebo product or Plenity.

The study was a double-blind, placebo-controlled study. This means neither the researchers nor the participants knew whether they were receiving Plenity or a placebo product until after the study was completed.

At the end of the study term, participants who had been using the Gelesis weight loss aid lost 6.4 percent of their baseline weight versus 4.4 percent in the placebo group. While not a large difference, it’s statistically significant.

What’s more, nearly 60 percent of people who took the Plenity capsules lost 5 percent of their weight, and 27 percent achieved weight loss greater than 10 percent of baseline.

In the placebo group, 42 percent of participants lost 5 percent of baseline body weight, and 15 percent lost 10 percent or more.

Participants using Plenity were twice as likely as placebo users to lose at least 10 percent.

And among participants with prediabetes or lifestyle-treated type 2 diabetes, people taking Plenity were six times more likely to lose 10 percent of their baseline weight by the end of the study.

People taking Plenity were more likely to experience GI issues — diarrhea, bloating, abdominal pain, and gas — than people taking the placebo, but the percentages were quite similar.

For example, 12.6 percent of people taking Plenity reported diarrhea compared to 8.5 percent of placebo users; 11.7 percent of Plenity users reported bloating compared to 6.6 percent of placebo users.

“In the past [there have been] multiple devices to put in your stomach to make you feel like there’s food in your stomach so you don’t want to eat more,” said Dr. Peter LePort, bariatric surgeon and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, California.

“They’ve always had some problem. Either they eroded the stomach or they passed into the intestines and they couldn’t get it out,” he said.

LePort notes that once the devices were removed, participants could start eating normally again, which often leads to weight gain. The devices could be installed again, but at a hefty cost.

LePort points out that Plenity, despite not having an established price point yet, is likely to be many times less expensive than surgery.

The preliminary studies on Plenity do show promising results, but long-term results are always the key for any and all weight loss products or plans.

Since the GLOW study was only six months long, time will tell how effective the device will be for people.

“In general, I consider these all some type of gimmick that the patient uses to take in less calories, because in the end, it comes down to calories. If you take in too many, you’ll gain weight. If you take in too little, you’re going to lose weight,” LePort said.

“If this device decreases the amount of calories you can take in a 24-hour period, then you’ll lose weight up to the point where you’re taking in the right amount of calories,” he added.

Gelesis says they’re eyeing a late-2019 limited launch with a nationwide release of their product in 2020.