Plenity Review: How It Works, Clinical Studies, Side Effects, and More

By HighYa Research Team
Published on: May 14, 2019

Plenity is an FDA-cleared weight-loss pill designed to give your stomach and intestines a full feeling so that you’ll eat less and, when combined with diet and exercise, help you lose weight.

While it was not available for purchase at the time of publishing, what’s most interesting about this pill is the method it uses to help you feel full, which is something we’ll explain in the next section.

The weight-loss treatment is the brainchild of Gelesis, the biotech company who developed the treatment. Gelesis’ CEO and founder is Yishai Zolar, a pharmaceutical entrepreneur who, along with Gelesis lead project scientist Dr. Alessandro Sannino, invented the treatment.

Five of the seven members of the company’s leadership teams have doctorate degrees. Two of those five have pharmacology doctorate degrees.

It is important for us to point out that the pill is not available at the time of publishing but Gelesis is encouraging individuals to express interest to their doctors. Later in this review, we’ll discuss how to handle decisions about treatments that aren’t available yet but are FDA-cleared.

In this review, we’ll explain to you how this weight-loss treatment works, what studies and the experts say about it and then conclude with a pros and cons list.

How Plenity Works

According to an explainer video intended for medical professionals, Plenity says that their pill is the result of 18 years of work and that it’s the only “super-absorbent hydrogel synthesized entirely from natural building blocks engineered to aid in weight management.”

In plain terms, each pill is filled with thousands of small little particles made from cellulose that absorb water in your stomach.

As they absorb the water, they expand up to 100 times their original weight and take on the consistency of food. The particles take up about one-fourth of the space in the average stomach, Gelesis notes in their Instructions for Use PDF.

Since the particles inside each Plenity pill expand, they take up more space in your stomach, leading to you feeling full quicker than you normally would. In theory you’ll stop eating.

At some point, your stomach transfers the food and Plenity particles into your small intestine, where your body assumes the particles are bits of food. Once they move through your small intestines and get into your colon, the particles dissolve and release back into your body the water they absorbed.

As we’ll talk about in the next section, Plenity doesn’t use particular drugs to curb fat production or to attack fat cells. Rather, it’s intended to reduce your appetite by filling your stomach with naturally-created, water-absorbing particles.

How to Take the Pills and Manage Your Weight

The instructions PDF on the Plenity website indicate that patients should take three pills (2.25g) with water 20 to 30 minutes before lunch and dinner. After swallowing them, drink an additional 16 ounces of water, which equtes to two standard-sized glasses.

Those same instructions indicated that Plenity needs to be used in conjunction with a “structured weight loss program” in order for it to be effective.

“Failure to adhere to prescribed dietary and exercise instructions may result in failure to lose weight,” the instructions note.

Who Plenity Is Good For?

According to the Plenity website, this product is intended for individuals who have a body mass index of between 25 and 40.

“Body mass index”, or, “BMI” refers to a figure calculated through dividing your weight in kilograms by your height in meters multiplied once by itself.

The CDC notes that there are two different calculators: one used for adults 20 and older and one used for children and teens between two years old and 19 years old.

Adult BMI ratings fall into four categories, per the CDC:

  • Below 18.5: Underweight
  • 18.5–24.9: Normal/healthy weight
  • 25.0–29.9: Overweight
  • 30.0 or above: Obese

Based on this data, Plenity is targeted for those who are on the low threshold of being overweight (25 BMI) and those who are obese but do not exceed a BMI of 40.

Statistics from the National Institute of Diabetes and Digestive and Kidney Diseases indicate that two out of every three Americans is overweight or obese. Therefore, it seems that there is a wide swath of the population who could be eligible for this pill, with the caveat that some of those who are “obese” may not be eligible for Plenity since their BMI may be more than 40.

Who Shouldn’t Take Plenity and What Are Its Side Effects?

At the time of publishing, Gelesis noted that there are certain types of people for whom Plenity may not be a good fit. Those people are as follows:

  • People with Crohn’s disease
  • People with anomalies in their esophagus
  • Those with allergies to cellulose, citric acid, sodium stearyl fumarate, gelatin or titanium dioxide
  • People with “prior gastrointestinal surgery” that may affect your GI tract

They caution those with GERD, ulcers or heartburn who want to use the pill, as it seems these types of people may experience some adverse effects.

That being said, the studies required to become FDA-cleared revealed that those who took Plenity experienced the same adverse effects as those who took a placebo (sugar pill).

Also, of great importance is that the healthcare professional instructions on the Plenity site indicate that they don’t know how Plenity will react with all other medications. Therefore, the instructions note that “all medications that are taken once daily should be taken in the morning or at bedtime as prescribed by your physician.”

As far as side effects go, conditions that participants from both groups experienced ranged from bloating, constipation and diarrhea to gas, nausea and headaches. According to the instruction guide, symptoms that were more common in the Plenity group experienced were:

  • Bloating
  • Abdominal pain
  • Diarrhea
  • Gas
  • Infrequent bowel movements

What Does “FDA-Cleared” Mean?

The FDA has three classes of medical devices and medications. The first class of items includes things like stethoscopes; very innocuous. The second class of treatments and devices are more complex and this is where Plenity falls, according to an FDA letter sent to Gelesis notifying them of their Class II clearance.

What this means is that there were enough products available to the public that were similar enough to Plenity that they approved it because of the similarities. Class II clearances don’t undergo the same type of scrutiny as Class III drugs and devices, who, when cleared, get the “FDA-approved” designation.

The Studies Behind Plenity

Plenity’s site features data from two different studies Gelesis commissioned to test the treatment’s effectiveness.

The first test, called the “GLOW” lasted six months. In those six months, they gave 223 participants Plenity while 213 received a placebo. The average weight of those taking Plenity was around 215 pounds and the average age was around 48 years old, whereas the placebo participants averaged about 222 pounds and 48 years old. The participants, according to the study, had to exercise and reduce caloric intake as part of the trial.

At the end of the study, they compared the weight-loss results from those on the treatment and those not on it. They found that six of out 10 of those taking Plenti lost an average of 22 pounds and that all of them experienced at least 11 pounds. They go on to say that one in four participants lost at least 30 pounds.

What’s important to note is that, because participants in both groups were required to exercise and follow diet guidelines, the placebo group lost weight, too. The study went on to point out that the Plenity group lost about six pounds more than the placebo group and they lost an average of 2.64 inches in the waist as opposed to 1.98 inches in the placebo group.

In total, the study said that the Plenity group lost an average of 6.41 percent of their body weight while the placebo group lost 4.39 percent.

This tells us that simply by reducing caloric intake and exercising, the group not taking Plenity was able to lose weight and that taking Plenity helped them lose an additional 2 percent, more or less, of their body weight.

We spoke to two separate experts to verify our interpretation of the results of the Gelesis study. Both board-certified Dr. David Belk and neuroscientist Dr. Andrew Neff confirmed that fact that the Gelesis study concluded that participants on Plenity lost about two percent more than those on Plenity.

When you take into account the average weight of those on the pill and those on the placebo, the study’s data concludes that those on the pill lost an average of 13.78 pounds based on participants’ average starting weight. The placebo group, on the other hand, lost an average of 9.74 pounds.

The key here is that those taking the pill lost about four more pounds than the placebo group over the course of six months. In other words, Gelesis’ study shows that those taking Plenity lost less than a pound a month more than the control group.

With these numbers in mind, you have to consider whether or not you want to pay for a new treatment whose own studies show you can lose an extra 1.5 pounds a month over someone who reduces their caloric intake and exercises without Plenity.

At the time of publishing pricing for this treatment was not available, so we can’t give you an accurate estimation of the cost-benefit of taking Plenity.

Will Plenity Work? The Experts Offer Their Opinions

As a consumer who may be interested in this treatment, where does all this leave you? To get the answer, we reached out to Belk.

“Does it work? According to the study done by the manufacturer (Gelesis), yes, but their study was conducted over only six months. That certainly appears promising, but it’s hard to know if anyone who loses weight this way will likely keep it off,” Belk said. “If not, I don't foresee any long-term benefit of this particular therapy. Even so, I’m sure lots of people will want it, at least initially.”

Neff, whose doctoral work focused on how serotonin affects appetite and weight loss, said that Plenity seems to work in the same way that fiber would. He goes on to say that one of the advantages of Plenity is that it doesn’t use ingredients that can affect your brain and present serious side effects like weight-loss drugs and pills that affect serotonin.

“Maybe this drug isn’t entirely different from just eating more fiber, however, it definitely strikes me as potentially more benign than serotonin-altering drugs which are typically/always associated with side-effects,” Neff told us. “If this drug is just mechanically operating on the stomach, it seems like a welcome advance from the existing drugs.”

The Final Word: Pros and Cons of Plenity

All of the research we gathered via Gelesis’ own documentation, as well as the input of two doctors, tells us that there are a distinct set of advantages and disadvantages.

First, the advantages. As Dr. Neff pointed out, Plenity doesn't seem to have the same side effects you’d get from taking a drug that would alter something in your mind to control hunger.

Second, we like the fact that Gelesis says that you have to exercise and maintain a calorie-restricted diet in order for Plenity to work well. This is important, in our opinion, because the calorie-reduction should make you more aware of what you eat and why. And, coupled with the exercise requirement, using the pill as part of a weight-loss regimen can build good habits that may benefit you beyond when you stop taking Plenity.

As for the disadvantages, we believe, based on Gelesis documents, that the average person may only see a four-pound advantage in taking Plenity over someone who takes up the same diet and exercise routine but doesn’t take Plenity.

Depending on how much the drug will cost you via your insurance plan, the money you’re paying per month may not be worth the slight advantage you have in losing weight per month.

Now, this comes with a caveat. Some who participated in the study reported weight loss of more than 20 pounds over the course of the six months they took Plenity.

Because each body is different and each patient will take a different approach for the diet and exercise the treatment calls for, the results will vary and you may, in fact, experience significant weight loss.

At the very least, as we mentioned a few seconds ago, Plenity’s requirement that you change your diet and exercise will teach you some of the basic habits that can lead to life-long health.

If you want to learn more about simple exercises you can do to keep you healthy, read through our article about the benefits of walking 30 minutes a day. In it, we talk with doctors and do in-depth research to show you just how much the simple act of walking can increase your quality of life.

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