Direct Measurement of Ingestive Behaviour in Relation to Sex Differences and Gastrointestinal Hormone Levels in Patients After Metabolic and Bariatric Surgery (DIBASH)

May 14, 2026 updated by: Marco Bueter, University of Zurich

Bariatric surgery (BS), especially procedures like Sleeve Gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB), is the most effective treatment for obesity. Yet, the exact mechanisms governing its effect are somewhat elusive, with current research mainly focusing on post-operative food intake outcomes based on self-reported data, which might not fully capture the nuanced changes in eating behaviours.

To address these gaps, our study plans to employ the newly developed "drinkometer", a device capable of analysing the intricate changes in drinking behaviour following BS. This tool promises to bring a more detailed perspective to the changes in ingestive behaviours, bypassing the inaccuracies of self-reporting methods. By expanding our research to encompass diverse patient demographics and examining potential links to physiological shifts like gut hormone level alterations, the study aims to provide a more rounded understanding of the long-term impacts of BS on eating behaviours.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

HYPOTHESIS AND PRIMARY OBJECTIVE

So far, studies of ingestive behaviour in humans have produced ambiguous results. Moreover, direct measurements of ingestive behaviour in humans after BS are still rare and the roles of sex and gut hormones, as well as their relevance for clinical outcome parameters, such as body weight loss, remain elusive. A comprehensive understanding of how a given intervention such as BS affects food intake requires a detailed analysis of the ingestive behaviour itself, not simply the measurement of the outcome of the behaviour. In other words, the information on how the food is consumed is equally or even more important than the information on how much food has been ingested.

This study employs the drinkometer methodology to perform direct measurements of ingestive behaviour in male and female human patients after SG and RYGB along with parallel measurements of postprandial gut hormone levels. Furthermore, this study investigates the clinical relevance of changes in ingestive behaviour by correlating microstructural parameters with body weight loss in a consecutive set of patients who received RYGB at the University Hospital Zurich five years before the time of recruitment.

Of note, the proposed experiments aim to test specific hypotheses regarding the behavioural mechanisms underlying potential changes in food intake after BS in humans. Thus, this research do not aim to identify how BS affects one or the other single microstructural parameters of eating or drinking. Instead, this study investigates how a given intervention that is known to substantially affect food intake behaviour - such as BS - alters the profile of a group of microstructural parameters of ingestive behaviour in humans. Given that ingestive behaviour represents the readout of the central nervous system mechanisms controlling energy intake (e.g., palatability, aversion, avoidance, satiation), the results of the proposed studies will inform the search for the underlying neural circuits in the brain that are specifically altered by BS. If there is no altered behaviour, there would be no point in investigating the underlying physiology. More specifically, this study aims to:

  1. Investigate longitudinal changes and differences in the ingestive behaviour of female patients before and within one year after either primary RYGB or primary SG (Study 1).
  2. Investigate a possible association between the ingestive behaviour and the prandial gut hormone levels of female patients before and within one year after either primary RYGB or SG (Study 1).
  3. Investigate a possible difference between the ingestive behaviour of female and male patients before and within one year after primary RYGB (Study 2).
  4. Investigate a possible association between the postoperatively achieved body weight loss of female and male patients 5 years after primary RYGB and ingestive behaviour (Study 3).
  5. Investigate, in a subset of responders and non-responders to primary RYGB, a possible association between postprandial gut hormone levels of female and male patients 5 years after primary RYGB and ingestive behaviour (Study 3).

PRIMARY AND SECONDARY ENDPOINTS

In the research protocol, the primary and secondary outcomes specific to each of the three studies planned within the research project have been described. Recognising that each study has its unique objectives and hypotheses, the outcomes have been specified distinctly for each study to ensure clarity and focus in the research approach.

For each of the three studies, the primary outcomes are those key results that the study is primarily designed to assess. These are the main effects or findings that are anticipated to provide the most significant insights into the research questions. Secondary outcomes, while still important, are additional results that can be explored after answering the main research questions. These might provide supplementary information, support the primary outcomes, or offer insights into other areas related to the main research question.

By presenting these outcomes separately for each study, this study aims to provide a structured and transparent overview of the research intentions, allowing for a clear understanding of the objectives and measures in each specific part of the project. This approach not only aids in maintaining the focus and integrity of each study but also assists in the clear communication of the research goals and methods.

PROJECT DESIGN

The proposed studies will test key elements of ingestive behaviour and their relation to pre- and postprandial levels of gut hormones as well as sex differences after the two most frequently performed bariatric operations. They will thus provide useful information for planning and conducting future trials in the field, such as optimal recruitment and retention strategies, intervention delivery, data collection methods and adherence to study protocols. The proposed studies will further provide empirical estimates of effect sizes of bariatric surgery and long-term associations of ingestive behaviour with gut hormones for post-bariatric body weight loss. The potential outcomes of Studies 1, 2 and 3 are conceptually different. Nevertheless, the results of these studies will complement each other as well as our findings from previous studies, and can be used to calculate sample sizes for future trials.

Study Type

Observational

Enrollment (Estimated)

420

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

  • Switzerland
    • Canton of Zurich
      • Männedorf, Canton of Zurich, Switzerland, 8708
      • Zurich, Canton of Zurich, Switzerland, 8091
        • Recruiting
        • University Hospital Zurich, Department of Surgery and Transplantation
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

Yes

Sampling Method

Probability Sample

Study Population

Participants with obesity and scheduled for bariatric surgery are recruited consecutively at the outpatient clinic of bariatric surgery at the University Hospital Zurich.

Participants with obesity not scheduled for surgery are recruited at the private clinic "Adimed" in Winterthur.

Participants without obesity are recruited from students, employees and faculty of the Faculty of Medicine of the University of Zurich.

Description

Inclusion Criteria:

  • Age ≥ 18 year
  • BMI ≥ 35 kg/m2 for patients with planned RYGB or SG operation
  • BMI ≥ 30 kg/m2 for external controls affected by obesity but no planned RYGB or SG within the next 12 months, and
  • BMI ≥ 18.5 kg/m2 and ≤ 24.9 kg/m2 for controls without obesity.

Exclusion Criteria:

  • history of previous bariatric operations and/ or revisional surgery (e.g., alteration of limb lengths after primary RYGB),
  • smoking,
  • established diagnosis of type 1 or 2 diabetes mellitus, and
  • polycystic ovary syndrome (PCOS).

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Adult Females planned for RYGB surgery
Adult females leaving with obesity with BMI between 35 and 50 kg/m2 and scheduled for Roux-en-Y Gastric Bypass Surgery
Procedure: Bariatric Surgery
The intervention is not assigned to the participant after recruitment in the study, rather the intervention is an inclusion criteria for participation in the study.
Adult Females planned for SG surgery
Adult females leaving with obesity with BMI between 35 and 50 kg/m2 and scheduled for Sleeve Gastrectomy Surgery
Procedure: Bariatric Surgery
The intervention is not assigned to the participant after recruitment in the study, rather the intervention is an inclusion criteria for participation in the study.
Adult Females with Obesity
Adult females leaving with obesity with BMI between 30 and 50 kg/m2 but not scheduled for any procedures of bariatric surgery
Adult Females with Normal-Weight
Adult females with normal weight with BMI between 18.5 and 24.9 kg/m2
Adult Males planned for RYGB surgery
Adult males leaving with obesity with BMI between 35 and 50 kg/m2 and scheduled for Roux-en-Y Gastric Bypass Surgery
Procedure: Bariatric Surgery
The intervention is not assigned to the participant after recruitment in the study, rather the intervention is an inclusion criteria for participation in the study.
Adult Males with Obesity
Adult males leaving with obesity with BMI between 30 and 50 kg/m2 but not scheduled for any procedures of bariatric surgery
Adult Males with Normal-Weight
Adult males with normal weight with BMI between 18.5 and 24.9 kg/m2
Adult Females and Males 5 years after RYGB surgery
Adult Females and Males who underwent RYGB surgery 5 years before study recruitment and study measurements
Procedure: Bariatric Surgery
The intervention is not assigned to the participant after recruitment in the study, rather the intervention is an inclusion criteria for participation in the study.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Drinkometer Measurement of Microstructural Parameters of Ingestive Behaviour, such as Suck Energy Intake and Burst Energy Intake.
Time Frame: One year after bariatric surgery
Difference of the eleven microstructural parameters of ingestive behaviour within the cohorts with intervention at the end of follow-up compared to baseline measurements and differences between the cohorts with intervention and the cohorts without intervention will be measured with a drinkometer device. The microstructural parameters of ingestive behaviour are: mean suck energy intake (kcal), mean suck duration (s), mean suck rate (kcal/s), mean suck maximal rate (kcal/s), burst number (n), burst energy intake (kcal), burst duration (s), burst rate (kcal/s), number of sucks per burst (n), inter-burst intervals (s), and inter-suck intervals (s). On this platform, a separate entry for the eleven microstructural parameters is not done to avoid redundancy in the description.
One year after bariatric surgery
Effect of the Gut Hormones in Plasma on the Microstructural Parameters of Ingestive Behaviour Measured with the Drinkometer Device
Time Frame: One year after bariatric surgery
This study investigates the effect of pre- and post-prandial levels of gut hormones on the eleven microstructural parameters of ingestive behavior. These are: mean suck energy intake (kcal), mean suck duration (s), mean suck rate (kcal/s), mean suck maximal rate (kcal/s), burst number (n), burst energy intake (kcal), burst duration (s), burst rate (kcal/s), number of sucks per burst (n), inter-burst intervals (s), and inter-suck intervals (s). On this platform, a separate entry for the eleven microstructural parameters is not done to avoid redundancy in the description. The study focuses on the influence of the following gut hormones: leptin, ghrelin, cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1), gastric inhibitory polypeptide (GIP), amylin, peptide YY (PYY), and insulin. These hormone concentrations are measured both pre- and post-prandially in the blood and are expressed in their respective units of measure (e.g., leptin in ng/mL, ghrelin in pg/mL).
One year after bariatric surgery
Effect of Biological Sex (Male or Female) on the Microstructural Parameters of Ingestive Behaviour Measured with the Drinkometer Device
Time Frame: One year after bariatric surgery
This study investigates the effect of biological sex (male or female) on the eleven microstructural parameters of ingestive behavior. These parameters are: mean suck energy intake (kcal), mean suck duration (s), mean suck rate (kcal/s), mean suck maximal rate (kcal/s), burst number (n), burst energy intake (kcal), burst duration (s), burst rate (kcal/s), number of sucks per burst (n), inter-burst intervals (s), and inter-suck intervals (s). On this platform, a separate entry for the eleven microstructural parameters is not done to avoid redundancy in the description. The study focuses on comparing these parameters between males and females to understand the influence of biological sex on ingestive behavior.
One year after bariatric surgery
Cluster identification
Time Frame: Five years after bariatric surgery
Identification of clusters of good and poor response to RYGB five years after surgery based on the variance of the single microstructural parameters of ingestive behaviour
Five years after bariatric surgery
Correlation of Percentage Excess Body Mass Index Loss with the Microstructural Parameters of Ingestive Behaviour Measured with the Drinkometer Device Five Years After Roux-en-Y Gastric Bypass Surgery
Time Frame: Five years after bariatric surgery

This study aims to investigate the correlation between percentage excess body mass index (BMI) loss (%EBMIL) and microstructural parameters of ingestive behavior, measured using the Drinkometer device, five years after Roux-en-Y gastric bypass (RYGB) surgery. The eleven microstructural parameters considered are: mean suck energy intake (kcal), mean suck duration (s), mean suck rate (kcal/s), mean suck maximal rate (kcal/s), burst number (n), burst energy intake (kcal), burst duration (s), burst rate (kcal/s), number of sucks per burst (n), inter-burst intervals (s), and inter-suck intervals (s).

This study explores how these microstructural parameters of ingestive behavior correlate with the long-term success of RYGB surgery as indicated by %EBMIL. By understanding these correlations, we aim to gain insights into the behavioral mechanisms that contribute to the maintenance of weight loss post-surgery.
Five years after bariatric surgery

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of Zurich

Collaborators

University College Dublin
Florida State University

Investigators

  • Principal Investigator: Marco Bueter, MD, DPhil, University of Zurich

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

February 13, 2024

Primary Completion (Estimated)

August 31, 2027

Study Completion (Estimated)

December 31, 2027

Study Registration Dates

First Submitted

July 25, 2024

First Submitted That Met QC Criteria

July 31, 2024

First Posted (Actual)

August 6, 2024

Study Record Updates

Last Update Posted (Actual)

May 18, 2026

Last Update Submitted That Met QC Criteria

May 14, 2026

Last Verified

May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 2023-02109

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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