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Plenty of Plenity: a New Weight-loss Product?

Plenty of Plenity: a New Weight-loss Product?

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Have you heard of Plenity?

Is it a bird? Is it a plane? No, It is Plenity! The FDA-cleared weight-management aid! 

Ok, comparing Plenity to Superman might be grossly exaggerating it, but you know how I am a fan of the theatrics! Are you as confused as I was when one of my followers started asking me about this new weight-management product?

Surprise, surprise, it is really only available in the US. Quite frankly, I am not even entirely sure how one goes about obtaining Plenity down in the states. I do know you need a prescription, but after my brief google search, I am not sure if you go to a pharmacy for it or if you order directly from the Plenity website? It was a bit confusing.

Now I am based in Canada, so that might be a contributor. Still, if one of the company representatives ends up reading this, you might want to bring some clarity in this regard if you actually want to sell your product. I would recommend you also stop reading at this point as this might not be the hype piece for Plenity you are hoping for #sorrynotsorry #yolo! 

So, what is Plenity?! 

As described in the Gelesis Loss of Weight (GLOW) study by Greenway et al., Plenity or Gelesis100 is a non-systemic, superabsorbent hydrogel! English translation: It is a substance that one ingests, it stays in your digestive tract, it is not absorbed into the body, and it acts like a super sponge – soaking up all the water around it!

As the Plenity website states, it is made from naturally derived building blocks and has been proven by science! Those naturally derived building blocks are cellulose and citric acid that are made into the 3D matrix of super absorbent power. Cellulose comes from plants, in particular, green plants. It is a form of fibre, the kind we humans cannot digest but is necessary for gratifying bowel movements and function. And citric acid? I am sure you have heard of it in the context of citrus fruits. It provides the wonderful tart, sour taste that helps to cut the gut-wrenching taste of bad tequila. But, unfortunately, it does not help with the questionable actions and future regrets that soon follow 1 to 10 shots of tequila. So yes, Plenity has two ingredients that occur naturally in nature, as separate ingredients. Gelesis, the company that created Plenity, did some chemistry stuff and created Plenity, a naturally derived but man-made product.

As described in the GLOW trial Plenity is taken orally in the form of capsules ~20-30 minutes before a meal with water twice a day. The Plenity particles then get to work in the stomach absorbing as much water as possible and mixing with the ingested food. Now Plenity does not form into one large mass. This would be no bueno from a bowel movement perspective. Instead, it forms thousands of small individual gel pieces that have the firmness of solid ingested foods like vegetables but have 0 caloric value. It is noted, at the recommended dosage, Plenity, when hydrated, will occupy 25% of your stomach volume. The gel pieces then maintain their integrity through the digestive tract until they reach the large intestine. Here they are broken down, the water is released, and Plenity is then evacuated with your next bowel movement.

Plenity is considered to be a weight-management device vs. a drug because its effects in the body and its weight management properties are purely mechanical. It takes up space in your stomach, so you eat less. It is not binding to receptors or altering your body’s normal physiology in any way.

Is Plenity too good to be true?

Sounds pretty good, right?! Something that is naturalish just takes up space in your stomach, nothing else, and at the end of the day, you have a good poop and lose weight?! Well, yes and no, let me explain. The GLOW study, which was the landmark trial to demonstrate the safety and efficacy of Plenity, had a few issues, in my opinion.

The study was a randomized, double-blind, placebo-controlled trial over 24 weeks. English translation: there were two groups of people that had obesity, and each group was selected at random to receive either a sugar pill or Plenity. In the process of all this, no one had a clue who got what, including the researchers. The participants were also prescribed moderate-intensity exercise and a diet that was 300 calories below their daily calorie needs for weight maintenance. All pretty standard, right?! 

Right! However, my issue comes from a bit deeper analysis of the GLOW trial and, needless to say, there were a few red flags that made me question the results. And as I have learned from previous relationships, red flags are not to be ignored! No matter how pretty the rest of it seems.

So here are a couple of my issues: 

  1. The main randomized study period was only six months. Studies examining weight-loss interventions should really be at least 1-year in length. The reason being is that after 1-year this is when we see weight plateau and possible weight regain begin to occur. So if you cut it short, does that mean you don’t want us knowing about what happens beyond 6-months? Now, I will give the researchers some credit as they did a small extension trial for another 24 weeks called the GLOW-EX. The extension took people from both groups that lost >3% of their baseline body weight and provided them Plenity if they were in the placebo group or continued on Plenity if they were already taking it. (I will get to these results in a second!)
  2. A lot of people dropped out of the study. In the Plenity group, 23% of people dropped out. In the placebo group, 29% of the people dropped out. Well, why?! One of my professors back in the day, who was an evidence-based medicine guru, gave us a rule: if a study had a >20% drop-out rate, you should promptly throw it out. (I prefer recycling to, you know, save the planet etc., but you get what I am saying.) Greenway et al. noted that the most common reason for withdrawal was for lifestyle or personal choice. So maybe people dropped out because the study methods did not work for their lifestyle or the researchers were mean, and people dropped out to save their personal well-being?! The exact reasons are not mentioned. However, it makes me question the results of this study. If people in a perfect and controlled trial environment cannot stick to the treatment, how effective will this really be in ‘real-life’ situations, such as life, family, work, stress, etc.?! 

There were some other methodological flaws, such as significant differences between treatment groups and procedures on randomization. In addition, concealment was not explicitly stated, and the authors made no attempt to review the limitations of their study. Really, I am just nitpicking at this point, but when there are some initial red flags, I call everything else into question. 

Anywho, enough of me harping. What were the results?

What does the science say?

Both groups lost weight! The Plenity group lost ~6.41% and the placebo group lost ~4.39% of their body weight from baseline at 24-weeks. Nearly 60% of individuals in the Plenity group lost ≥5% of their baseline weight, and about 27% lost ≥10%. Which is not too shabby although the placebo group had decent success too with about 42% and 15% achieving the above results, respectively. This indicates that the lifestyle interventions prescribed were effective on their own.

Now for the interesting results from the GLOW-EX extension trial, where they took 39 individuals from the Plenity and placebo groups that lost >3% of their baseline body weight and provided or continued with Plenity.

They found that the individuals treated with Plenity in the first six months lost on average 7.1% from their baseline weight. And, when they continued with Plenity for another six months, they maintained their weight-loss and even lost a tad bit more with an average loss of 7.6%. Interestingly, the individuals selected from the placebo group lost an average of 7.1% from baseline in the first six months (sooo, did Plenity do anything?). And, when they were offered Plenity for the next six months, they went on to lose more weight and lost 9.4% of their weight from baseline on average.

Say what?!

So, did Plenity do anything?

This data implies that it is better to have an individual lose as much weight as possible with lifestyle interventions alone THEN provide them Plenity and they can achieve an even greater amount of weight-loss!? I mean, yes, we should look at optimizing lifestyle interventions before adding medications, but that isn’t always practical and reasonable. Again, this extension trial is an issue because the placebo group lost the same amount of weight as the Plenity to start individuals at week 24. That indicates to me the individuals in the placebo may be a little different. Perhaps higher self-efficacy? Less stress? More motivation? It is difficult to determine, but they likely made more lifestyle changes and were more consistent with them to achieve the initial weight-loss results and then achieve further weight-loss when Plenity was provided.

One must again question, did Plenity actually do anything for them? Unfortunately, that is impossible to say because the authors, of course, did not compare this group to a placebo.

Final Thoughts:

Ok, I am done. #sorrynotsorry to the Plenity team. I am sure you will not be hiring me anytime in the near future, and that is alright! In conclusion, Plenity is a tool in the toolbox. From a theoretical perspective, the product sounds good and seems like it should work. However, I don’t believe it is as effective as the results of the GLOW trial may indicate. It might be something to try. An alternative option might be to eat more veggies that can take up that space in your stomach, allowing you to eat smaller portions and provide some nutritional goodness at the same time!

Until next time my friends! Remember: small tweaks lead to massive peaks!

Dr. Dan



Greenway FL, Aronne LJ, Raben A, Astrup A, Apovian CM, Hill JO, Kaplan LM, Fujioka K, Matejkova E, Svacina S, Luzi L, Gnessi L, Navas-Carretero S, Alfredo Martinez J, Still CD, Sannino A, Saponaro C, Demitri C, Urban LE, Leider H, Chiquette E, Ron ES, Zohar Y, Heshmati HM. A Randomized, Double-Blind, Placebo-Controlled Study of Gelesis100: A Novel Nonsystemic Oral Hydrogel for Weight Loss. Obesity (Silver Spring). 2019 Feb;27(2):205-216. doi: 10.1002/oby.22347. Epub 2018 Nov 13. Erratum in: Obesity (Silver Spring). 2019 Apr;27(4):679. Erratum in: Obesity (Silver Spring). 2019 Jul;27(7):1210. PMID: 30421844; PMCID: PMC6587502.

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