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Plenity Is the New Weight Loss Drug in Town—Does It Work?

The FDA has approved a new weight loss drug. But will Plenity turn the tide against obesity? 

By
Monica Reinagel, MS, LD/N, CNS
Episode #557
weight loss
The Quick And Dirty
  • Plenity works by forming a harmless gel that takes up room in your stomach. 
  • Certain foods can work the same way.
  • But we don't always stop eating just because our stomachs are full. 
  • Foods or drugs that fill our stomachs may help with weight management but are unlikely to be the complete solution. 

Nutrition Diva listener John recently asked me to weigh in on a new FDA approved weight loss drug called Gelesis100.  The drug is not yet available to the public, but it will probably be coming onto the market very soon as a prescription-only drug under the brand name Plenity. I bet it’ll be hard to miss it when it does become available; there will probably be a huge advertising and marketing push.

But is this new drug going to be the one that turns the tide against obesity?

Previous pharmaceutical approaches to weight loss have all had major drawbacks. Stimulants like phentermine are effective in suppressing appetite, for example. But they can be habit-forming, not to mention that the pesky side effect of occasionally stopping your heart.  Other drugs such as orlistat (marketed as Alli and Xenical) are somewhat effective in blocking the absorption of fat and calories from foods. Unfortunately, they also block the absorption of fat-soluble nutrients, not to mention having a rather embarrassing side effect requiring frequent underwear changes.

Plenity is designed to reduce food intake by making you feel like you’ve had more to eat than you actually have.

This new drug takes a different approach that avoids the worst of these side effects. It is designed to reduce food intake by making you feel like you’ve had more to eat than you actually have.

The drug is made from two compounds that occur naturally in foods—cellulose and citric acid. You swallow three capsules with a big glass of water before meals. The capsules release particles in your stomach, which rapidly absorb water and expand to form a harmless gel. This gel has no calories, but it takes up room in your stomach and intestines. With less room in your stomach, the idea is that you’ll eat less and lose weight.

How well does Plenity work?

In a clinical trial, people who used Plenity and also followed a reduced-calorie diet and exercised moderately lost more weight on average than those who reduced calories, exercised, and took a placebo. About 20% of those in both groups dropped out before the end of the trial, which was scheduled to last about six months. Of those who completed the six months, the group taking Plenity lost about 6% of their weight, while the group taking a placebo lost about 4%. 

The group taking Plenity lost an average of 14 pounds while the placebo group lost an average of 10 pounds. So, we’re only talking about four extra pounds over 6 months.

So, you could say that people taking the drug lost 50% more weight, which sounds really impressive. However, the actual weight loss was pretty modest in both groups. The group taking Plenity lost an average of 14 pounds while the placebo group lost an average of 10 pounds. So, we’re only talking about four extra pounds over six months.

Even though the people taking Plenity didn’t lose a whole lot more weight than the people who didn’t, it’s certainly possible that they found it a bit easier to stick to their diets because they weren’t as hungry. Unfortunately, the researchers didn’t report on things like perceived hunger or how difficult the subjects found it to stick to their diets.

They did assess safety and side effects. There were no big concerns about safety, but the group taking the drug definitely reported more side effects than the group taking placebo. Most of these were digestive symptoms like diarrhea, bloating, gas, constipation, or abdominal pain. And most of these were considered mild in severity.

Ways to feel full without drugs

There are non-pharmaceutical ways to make your stomach feel a bit fuller. Researcher Barbara Rolls has popularized an approach known as Volumetrics. The idea here is to choose foods that have a lot of volume but not too many calories. Primarily, these are foods that contain a lot of fluid or a lot of fiber: soups, broths, whole vegetables and fruits, whole grains, and that sort of thing. Even just drinking a full glass of water before meals has been shown to decrease food intake.

Even just drinking a full glass of water before meals has been shown to decrease food intake.

These volumetric foods trigger special cells in your stomach that register pressure or fullness. These then send a signal to your brain that you’ve had enough to eat. (Presumably, this feature is designed to prevent us from eating until our stomachs literally explode.) But because these foods and liquids don’t contain a lot of calories, you end up reducing your calorie intake and losing weight. It’s the same concept as Plenity. Only it involves healthy foods instead of drugs. 

The problem with Plenity

One of the potential drawbacks of Plenity is that you’d presumably have to keep taking it indefinitely to maintain your weight loss. I’d rather get used to eating a certain way that helps me maintain my weight than commit to a lifetime of pharmaceutical support.

But neither Plenity or Volumetrics addresses the elephant in the room—we don’t always stop eating just because our stomachs feel full.

Think back to the last big holiday meal you enjoyed. How full did your stomach feel as you finished Thanksgiving dinner, for example? Was there really room for a piece of pie? Did that stop you? Maybe it did! But I think you get my point.

I’d rather get used to eating a certain way that helps me maintain my weight than commit to a lifetime of pharmaceutical support.

We eat when we’re not hungry all the time! In fact, I’ll go one step further and suggest that we consume the majority of excess calories responsible for our unwanted weight when we’re not really hungry.

We eat because we’re bored or sad or procrastinating. Or simply out of habit. We eat because it’s time to eat or because those around us are eating. Or because something appetizing appears. Often, we’ll keep eating until our plate is empty. We’ll eat way past the point at which our physical hunger is satisfied, or our stomachs are full. And no drug or bowl of soup is going to remove that impulse or desire.

Choosing foods that fill us up for fewer calories is a great strategy for weighing less. But it’s rarely the complete solution. Usually, we also have to work on our habits, adjust our environment, and address emotions and other non-hunger related issues that lead to overeating.

Similarly, a drug that fills our stomachs will gel is unlikely to be a silver bullet against obesity. We’ll still have to figure out all the other stuff if we want to achieve permanent weight loss. And, frankly, while the benefits of this drug may have cleared the bar for statistical significance and drug approval, the actual impact on weight loss was pretty  modest, especially when we can exploit that same effect through non-pharmaceutical means. 

A drug that fills our stomachs will gel is unlikely to be a silver bullet against obesity

What do you think? If you occasionally (or regularly) overeat, how much of a role does your physical hunger play in this behavior? Would a physical sensation of fullness keep you from eating more of something you really enjoy? Or from finishing whatever's on your plate? Or from turning to food for emotional comfort?

If so, maybe Plenity would be useful. But. seeing as the drug is not yet available, why not use this time to try the same approach with foods? You can check out Barbara Rolls’ book The Volumetrics Eating Plan or simply go back in the Nutrition Diva archives and look up episode #126, How to Eat Less Without Feeling Hungry and episode #223 on Satiation and the foods that make you feel full.

Then, report back. I’d love to hear what you discover. You can email me at nutrition@quickanddirtytips.com or join the discussion on my Facebook page. I look forward to hearing from you!

If you’re looking for more resources and support for sustainable weight loss, Brock Amstrong (the Get-Fit Guy podcast) and I run a private Facebook group devoted to this topic. You can find it on Facebook by searching for Weighless Life.

About the Author

Monica Reinagel, MS, LD/N, CNS

Monica Reinagel is a board-certified licensed nutritionist, author, and the creator of one of iTunes' most highly ranked health and fitness podcasts. Her advice is regularly featured on the TODAY show, Dr. Oz, NPR, and in the nation's leading newspapers, magazines, and websites. Do you have a nutrition question? Call the Nutrition Diva listener line at 443-961-6206. Your question could be featured on the show. 

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