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Orlistat vs Plenity: What's the Difference?

Orlistat vs Plenity: What's the Difference?
Dr. Constance Odom, MD Picture of Dr. Constance Odom, MD

Medically reviewed by

Written by our editorial team.

Last Edited 5 min read

According to studies, approximately 95% of all diets fail with any weight loss ultimately being regained after a period of 1 to 5 years. With two-thirds of American adults being overweight, a better solution is needed to help these individuals regain control of their health. While there are countless exercise regimes, surgeries, and even supplements that claim to provide fast and long-lasting results, these methods have varying results. Likewise, most weight loss methods are most effective when they combine several aspects, such as a healthy diet and regular exercise. 

Those who have struggled to lose weight or keep it off after trying these tactics may be surprised to learn that there are a number of weight loss medications on the market today. While the majority of medicines prescribed for weight loss are done so off-label, there are two popular weight loss medications that come along with a seal of approval from the Food and Drug Administration (FDA). They are known as Orlistat and Plenity. Although a doctor is likely to recommend one or the other based on individual patient circumstances, there are distinct differences between the two that should be considered by those who are overweight.

What is Orlistat?

Orlistat is commonly recognized and distributed under the brand names Alli or Xenical. The FDA first approved Xenical in 1999 as a prescription medication for weight loss. The dosage for this approval was 120 mg and was reserved for those who consulted their doctors for a weight loss solution. Years later in 2007, the FDA approved a 60 mg dose of Orlistat to be offered as an over-the-counter weight loss medication. Under the brand name Alli, Orlistat quickly gained popularity as a simple and effective solution for those seeking weight loss aid. 

How Does it Work?

Typically, when a person eats, fats that they consume are absorbed when they reach the small and large intestines. This is transformed into energy that the body needs to function properly by an enzyme known as lipase. When someone takes in more fat than their body needs for energy, lipase instead stores the fat within the body. This results in the person being overweight. To combat this problem, Orlistat works by preventing the lipase enzyme from absorbing these fats. Because the fat that the person eats is not absorbed, it decreases their overall caloric intake. When fewer calories are taken into the body, the user of the medication is able to quickly and effectively lose weight. Despite this, Orlistat is not a quick fix for those who are overweight or obese. It must be incorporated into lifestyle changes that include a low-fat and low-calorie diet and regular exercise. This will allow maximum efficacy of the Orlistat medication while limiting some of the side effects associated with not adhering to the recommended diet.

Side Effects of Orlistat

Orlistat, like most medications, does come with the risk of side effects. In most cases, these side effects are mild and eventually subside as the patient’s body adjusts to the medication. Some of the most common side effects reported by users of Orlistat include:

  • Cold-like symptoms (runny nose, nasal congestion, and sore throat)

  • Muscle aches and pains

  • Vomiting

  • Nausea

  • Diarrhea 

  • Headache

  • Fecal incontinence

  • Bladder pain

  • Upper respiratory infection

  • Tiredness

  • Fever

  • Ear congestion

  • Sneezing

  • Pain in the back or side

  • Sweating

  • Insomnia

  • Shivering 

  • Loss of voice

While mild side effects can be bothersome, in most cases, they do not require immediate medical attention. You should, however, mention these side effects to your doctor during your next checkup. In some cases, it may be necessary to adjust the dosage of the medication or discontinue use altogether if the medication is causing significant discomfort. If you are taking an over-the-counter version of Orlistat, be sure to inform your doctor and seek approval. Orlistat, even OTC varieties, is not for everyone and may cause interactions with other medications or health conditions.

In extreme scenarios, it is possible for severe adverse reactions to this medication to occur. If any of these side effects are experienced after taking prescription or over-the-counter Orlistat medications, seek immediate medical attention:

  • Difficulty breathing

  • Chest tightness

  • Severe stomach pains

  • Wheezing

  • Blood in urine or stool

  • Rash

  • Swelling of the face, neck, throat, hands, or feet

Who Can Use Orlistat?

Orlistat is approved for use in adults and children who are at least 12 years old. Those who are prescribed Orlistat have Body Mass Index (BMI) measures that are at least 28 with a weight-related health problem (such as type 2 diabetes or high blood pressure) or 30 or more for those with no related conditions. Orlistat is not recommended for use by women who are pregnant or breastfeeding, along with those who have certain conditions that interfere with the digestive system, such as cholestasis or malabsorption disorders. The way that Orlistat functions means that certain vitamins or nutrients may not be absorbed by the body effectively when taking this medication and it may also interfere with other medications. Those with existing conditions should consult their doctors before taking any dose of Orlistat (including over-the-counter) to ensure that it is safe and will not cause interactions with their current medications.

What is Plenity?

Gelesis100, distributed under the brand name Plenity, is a prescription weight-loss aid that was approved by the FDA in April 2019. Unlike other weight-loss supplements, Plenity is not a medication and is instead classified as a weight-loss device. Like a medication, however, it comes in capsule form and is taken orally. The capsules are filled with hydrogel particles and must be taken with water to be effective for weight loss purposes. 

How Does it Work?

Plenity or Gelesis100 is a unique weight loss solution because it does not contain traditional medications. Instead, each capsule contains hydrogel particles. When they are ingested and the patient drinks the recommended amount of water with the capsule, the gel particles then expand within the stomach. This causes the patient to feel fuller faster, which decreases their appetite and their overall caloric intake. The capsules are taken twice per day, before lunch and again before dinner, to help users stick to consuming fewer calories each day. As the gel particles make their way through the digestive system, they ultimately dissolve and are passed along with regular bowel movements. 

Side Effects of Plenity

Plenity is not a traditional medication and in clinical studies was shown to have the same side effects as those who received placebos. Despite this, it is possible for mild side effects to occur after ingesting the hydrogel particles. These symptoms are mild and include diarrhea, constipation, flatulence, and a distended abdomen. If serious symptoms occur, such as allergic reactions, difficulties breathing, or severe pain, patients should seek immediate medical attention.

Who Can Use Plenity?

Plenity is not recommended for women who are pregnant or breastfeeding and should not be used by those with allergies to cellulose, citric acid, sodium stearyl fumarate, gelatin, or titanium dioxide. Those who have certain medical conditions or who take daily medications should consult with their doctor before taking Plenity to ensure that it will not affect the absorption of their medications. Plenity is intended for use by adults 18 and older who have a BMI between 25-40. Patients who take Plenity must also agree to follow a reduced calorie diet, exercise for 30 minutes or more each day and drink water after consumption of the hydrogel particles as directed by their doctor.

Key Differences Between Orlistat and Plenity

Ultimately, Orlistat is a more widely used medication for weight loss simply because it has been available on the market much longer than Plenity. The results for each vary widely depending on the patient’s specific circumstances and other health concerns. Additionally, regardless of which weight loss aid is used, it is crucial that patients who are taking either of these supplements also follow the diets and exercise regimes recommended by their doctors. This will help to maximize the amount of weight that is lost while taking these weight loss aids.

When it comes to the overall efficacy of taking Orlistat at the maximum recommended dose of 120 mg three times a day, the body will block the absorption of around 30% of the fats consumed each day. Patients who take Orlistat typically notice results within two weeks of taking the medication and most report losing anywhere from 5-10 pounds within the first six months. With continued treatment and an effective diet and exercise regime, those who take Orlistat generally lose around 10-20% of their body weight

By comparison, 6 out of 10 people who took Plenity during clinical studies lost between 5-10% of their body weight over the course of 6 months. Although the time it took users to see results varied, nearly all of the participants reported noticeable results within 4 weeks when paired with diet and exercise. Likewise, while Orlistat has been around for decades, Plenity is a cutting-edge medical device that is lesser known. A lot of research is still being done when it comes to the long-term effects and overall efficacy of Plenity, but experts report that the data that they have uncovered so far is promising. 

Which One is Right for You?

While the results are fairly similar, the biggest difference between the two comes down to their composition, their mechanism of action, and the side effects that they cause in patients. For example, those who are looking for a medication-free weight loss aid with few side effects may opt for Plenity. On the other hand, those who want a well-established weight loss medication to aid in reducing excess weight for medical purposes may prefer Orlistat. Aside from user preference, it is important to consider factors such as existing health conditions, diet, and BMI when choosing which solution is best. Your doctor is the best resource for helping to identify which weight loss solutions will align best with your medical history and overall weight loss goals. Be sure to mention any concerns that you may have and share any medications, vitamins, or supplements that you are currently taking before taking Orlistat or Plenity. 


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This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your physician about the risks and benefits of any treatment. Nu Image Medical may not offer the medications or services mentioned in this article.