A recent clinical trial demonstrated the efficacy of Gelesis100 use for weight loss (Obes 2019;27:205-216). The present trial is designed to explore the mechanisms by which it may work, i.e. by suppressing hunger, altering food intake and/or altering the efficiency of energy extraction from food.

Overweight/obesity is prevalent and associated with multiple adverse health outcomes. Moderating energy intake is one approach to lose or maintain body weight. To improve the probability of long-term adherence to an energy restricted diet, it is important to address the issue of appetite control. Numerous food components and properties have been explored for their satiation/satiety value. Two physical properties known to impact appetite are viscosity and elasticity (properties common to many dietary fibers). These properties may work by multiple mechanisms including prolonged gastric distention after a meal and slowed gastric emptying resulting in moderated swings in blood glucose and insulin concentrations. These properties may also alter the efficiency of energy absorption.

The present trial will test the effects of Gelesis100, a FDA cleared superabsorbent hydrogel, on the mechanisms just noted. Gelesis100 is nonsystemic and works directly in the gastrointestinal tract. Gelesis100 is made from two natural ingredients, cellulose and citric acid, that form a three-dimensional matrix designed to occupy volume in the stomach and small intestine, to create a sensation of fullness. The capsules disintegrate in the stomach and release the Gelesis100 particles, which can hydrate up to 100 times their original weight. When fully hydrated, the Gelesis100 particles occupy about a quarter of average stomach volume (although this may vary based on body size and various other factors). Without increasing the caloric value of a meal, Gelesis100 particles mix with ingested foods and create thousands of small, nonclustering individual gel pieces. The gel particles mix with ingested foods, creating a larger volume with higher elasticity and viscosity in the stomach and small intestine, promoting satiety and fullness. Gelesis100 has been cleared by FDA through the 510k de novo process and is marketed as a prescription medical device for weight management under the trade name Plenity™. A recent clinical trial demonstrated the efficacy of its use for weight loss (Obes 2019;27:205-216). The present trial is designed to explore the mechanisms by which it may work, i.e. by suppressing hunger, altering food intake and/or altering the efficiency of energy extraction from food.

Inclusion Criteria:

• Age 18-60 years (this is to reduce the number of people who apply that are taking medications or have chronic diseases).
• BMI =25-40 kg/m2

Exclusion Criteria:

• Body weight fluctuation of >5kg in the past 3 months
• Participant is allergic to or objects to consuming CMC, Citric acid, Sodium stearyl fumarate, titanium oxide, or gelatin.
• Participants with esophageal anatomic anomalies including webs, diverticuli, and rings
• Participants with suspected strictures (such as patients with Crohn's disease)
• Participants with complications from prior gastrointestinal surgery that could affect GI transit and motility
• Participants with active gastrointestinal conditions such as gastro-esophageal reflux disease (GERD), ulcers, or heartburn
• Participants taking prescribed medications

Treatment with Gelesis100 or placebo will be double-blinded and randomly assigned.