The Principal Investigator left the University of Colorado

The disease obesity continues to be a major health issue in the US with over one third of the population having a mass index >30 kg/m2. Obesity is associated with serious cardiometabolic complications including diabetes, hypertension, dyslipidemia and myocardial infarction. Rates of successful obesity treatment with weight loss and weight maintenance remain low. Several endoscopic bariatric therapies and procedures have been approved for use in the United States, including three intragastric balloon systems (2 fluid-filled and one gas-filled) and endoscopic sleeve gastroplasty (ESG), both of which have lower risks than bariatric surgery and do not alter gastrointestinal anatomy. Weight loss with all intragastric balloons and ESG is higher than lifestyle therapy or weight loss medications, but less than bariatric surgery. Unlike weight loss medications where weight loss from the medication is regained within 6-8 months after therapy ends, weight loss maintenance with intragastric balloons remains high with 66-88.5% of the weight loss maintained 6 months after device removal. Data suggests that space occupying devices with a volume of 400 ml or more in the stomach increase feelings of fullness and result in weight loss, but this does not explain the prolonged effect of weight loss maintenance after balloon removal. Although few studies have investigated the mechanism of action of fluid-filled balloons and one study with 4 patients undergoing ESG on weight loss, these data suggest that gastric emptying as well as space occupation contribute to weight loss. However, no studies have investigated the mechanisms of action of gas filled intragastric balloons on weight loss.

Understanding the mechanisms responsible for weight loss with the gas filled intragastric balloon system and ESG as well as any weight loss independent effects on blood glucose control would lay the groundwork for studies evaluating predictors of response to improve patient selection as well as studies understanding the mechanisms behind weight loss maintenance and developing strategies to prolong weight loss maintenance.

Therefore, the purpose of this pilot study is to determine the effects 10% total body weight loss (%TBWL) in patients with obesity treated with the intragastric balloon (GF- IGB) system or ESG compared to patients with obesity treated with a meal replacement program (MRP) on 1) gastric emptying, 2) hormonal adaptation to weight loss and 3) hunger.

Obesity is a chronic disease, which is associated with and contributes to multiple medical co- morbidities including but not limited to cardiovascular disease, diabetes, nonalcoholic fatty liver disease, and many different cancers. Obesity is also associated with an increased risk of all-cause mortality. Despite these known risks, treatment remains limited. This has contributed to the increase in the prevalence of obesity with 42.4%% of adults in the US adults having a body mass index (BMI) >30 kg/m2.

Endoscopic bariatric therapies are a new class of treatment for obesity, which have demonstrated more weight loss than lifestyle therapy alone and fewer complications than bariatric surgery with less weight loss than bariatric surgery. Four endoscopic devices are currently approved by the FDA for the treatment of obesity, including two intragastric balloons (IGB). One of the balloons systems are fluid filled (FF-IGB) and one is gas filled (GF-IGB). Although the GF-IGB system is swallowed, all the balloon systems require an endoscopist for endoscopic removal. In clinical registry series, these balloons demonstrate similar weight loss at 6 months. Unlike weight loss medications, weight loss maintenance is prolonged after IGB removal, which was demonstrated meta-analysis of studies and case series outside of the US of the single FF-IGB demonstrated weight loss maintenance after balloon removal 9 and in the US pivotal trials. While the occupancy of space in the stomach by IGB is known to induce satiation and satiety, this mechanism is only present with the IGB in place. Therefore, the prolonged effects of weight loss maintenance after IGB removal suggest other mechanisms contributing to weight loss with IGB treatment beyond space occupation. ESG is completed endoscopically with a device that has FDA 510k clearance for tissue apposition in the GI tract. Weight loss with ESG in a recent meta-analysis in 1772 patients demonstrated 16.5% TBWL at 12 months and 17.2% TBWL at 18-245 months. Understanding the mechanisms contributing to weight loss with the GF-IGB system and ESG will lay the groundwork for future studies to enhance the effect of IGBs and ESG on initial weight loss, patient selection, and weight loss maintenance; increasing benefits to patients treated with IGBs or ESG.

FF-IGB are known to delay gastric emptying. This is consistent with practice patterns as patients reliably have food left in their stomachs after an overnight fast requiring multiple days of liquid diet prior to endoscopic removal to avoid aspiration. In one study, the FF-IGB delayed gastric emptying compared to both baseline and a control group and the change in gastric emptying was associated with weight loss. Gastric emptying has been studied in only 4 patients before and after ESG. In these 4 patients, there was a 90-minute increase to the time for 50% of emptying of solid foods, however the limited number of patients in that study reduce overall certainty of the effect of ESG on gastric emptying. No studies have investigated the effects of the GF-IGB on gastric emptying. This protocol will clarify the effects of the GF-IGB and ESG on gastric emptying compared with a control group matched on weight loss. This will elucidate the weight loss independent effects of the devices since patients will be studied at baseline and 10% total body weight loss.

Another possible mechanism by which IGBs and ESG may induce weight loss and weight loss maintenance is through alterations in gut hormones. Ghrelin is a hormone secreted by X/A like cells, which are predominantly in the fundus of the stomach. Ghrelin concentrations fluctuate with eating, increasing pre-meals and decreasing in response to food in the stomach. Moreover, infusion of ghrelin stimulates eating in humans and is the only known hormone secreted from the GI tract to stimulate hunger. Weight loss with lifestyle therapy alone has been shown to increase fasting and meal test "active" or acyl-ghrelin concentrations, which correlated with increased hunger on visual analogue scale (VAS) testing. Acyl-Ghrelin concentrations were still elevated at one year after weight loss despite weight regain of almost 50%, which suggests that acyl-ghrelin plays and important role in weight regain. Studies investigating ghrelin concentrations in the setting of FF-IGBs have been mixed, demonstrating decreased fasting plasma total ghrelin concentrations, no change in fasting or meal test ghrelin concentrations in FF-IGB or control groups, increased fasting plasma ghrelin compared to a control group at months 1 and 6 with decreased ghrelin in the active arm compared to the control arm after removal and increased ghrelin concentrations in a single arm. However, these studies measured total ghrelin not acyl ghrelin. This limits the reliability of the data especially since no change in ghrelin concentrations were seen in control patients with weight loss in which an increase in acyl- ghrelin is expected. Moreover, all the studies were with FF-IGB and none were in the GF-IGB system.

Balloon type may have an effect on acyl-ghrelin concentrations, as GF-IGB tend to float in the fundus and body of the stomach, which may affect the IGB's ability to suppress acyl-ghrelin secretion. In one of the aforementioned studies a post-hoc analysis demonstrated that the small number of patients whose FF-IGBs localized to the fundus had greater suppression of ghrelin.

Fasting ghrelin has been evaluated in one study with 12 patients pre and post ESG. Fasting ghrelin concentrations did not increase with weight loss, but meal testing was not performed.

Therefore, this protocol will determine the effects of 10% TBWL from either GF-IGB system treatment or ESG treatment compared to lifestyle and meal replacement therapy on acyl-ghrelin concentrations, the active form of ghrelin, which stimulates hunger, and the sensation of hunger with the VAS. This will allow for the detection of effects that are specific to either procedure and independent of weight loss.

Inclusion Criteria:

• Male and female participants aged 22-65
• Weight Stable (<5% weight change in the last 3 months)
• Initiating treatment with GF-IGB, ESG, or medically supervised MRP
• BMI of 30-40

Exclusion Criteria:

• History of liver disease
• History of uncontrolled thyroid disease
• History of anemia
• History of diabetes
• History of eating disorder
• History of uncontrolled depression defined as a score of ≥ 10 on PHQ-9 (Patient Health Questionnaire-9)
• Use of weight loss medications in the past 3 months
• History of gastroparesis
• History of bariatric surgery
• History to allergy or intolerance to any component of the meal used in the gastric emptying study or mixed meal test
• Women who are pregnant or lactating
• Currently incarcerated
• Non English speaking
• Decisionally challenged adults