24-hour Clear Liquid Diet vs. Standard Fasting for Upper Gastrointestinal Endoscopy in Patients Taking Agonists of the GLP-1 Receptor
Retained Gastric Content · Delayed Gastric Emptying · Obesity · Type 2 Diabetes Mellitus (DM)
What this study involves
The registry does not currently label this study as recruiting. Ask about its status before planning a screening visit.
- Study type
- Interventional
- Phase
- Not applicable
- Age range
- 18 years - Not specified
- Sex eligible
- All sexes
- Healthy volunteers
- Not accepted
- Participants
- 250 Estimated
These are starting points, not an eligibility decision. The research team must review the full requirements.
About the research
GLP-1 receptor agonists delay gastric emptying and are associated with a higher rate of retained gastric content (RGC) during upper gastrointestinal endoscopy, even under standard fasting. No randomized trial has compared fasting strategies in this population. CLEAR-GLP1 is a multicentre, international, investigator-blinded randomized trial comparing a 24-hour clear liquid diet (followed by a 2-hour fast) with standard fasting (6 hours for solids, 2 hours for clear liquids) in adults on GLP-1 RA therapy undergoing elective upper endoscopy. GLP-1 RA therapy is not interrupted in either arm. The primary outcome is the rate of clinically significant RGC, defined as a GRACE stomach score of 0.
Read the full description
The primary objective of the study it to determine whether a 24-hour clear liquid diet protocol reduces the incidence of retained gastric content compared with a standard fasting protocol, graded endoscopically using a validated visibility scale (stomach GRACE score=0 vs. stomach GRACE scores=1, 2 or 3), in patients on GLP-1 receptor agonist therapy undergoing elective UGI endoscopy.
Who may be able to participate?
The list below is the sponsor’s full registry wording. It can include conditions, prior treatment, test results and other requirements. A match in search does not mean you qualify.
Inclusion Criteria:
- Age ≥ 18 years;
- Current treatment with a GLP-1 receptor agonist for at least 4 weeks, regardless of indication;
- Referral for elective upper gastrointestinal endoscopy (isolated or combined with colonoscopy);
- Informed consent for both the upper gastrointestinal endoscopy procedure and study participation.
Exclusion Criteria:
- Urgent/emergency endoscopy;
- Previously diagnosed gastroparesis;
- Prior major gastric/esophageal surgery (e.g., gastrectomy, gastric bypass);
- Known or suspected upper gastrointestinal obstruction;
- Pregnancy;
- Refusal or inability to comply with the assigned fasting protocol.
Treatment, groups and participation
The registry may describe treatments and study duration without a complete visit calendar. Ask the study team for the exact schedule, procedures, risks, costs and alternatives. Keep your usual care plan unless your treating clinician tells you otherwise.
- Assignment
- Random assignment
- Masking
- Double masked
24-Hour Clear Liquid Diet
24-hour clear liquid diet: exclusively clear liquids for the 24 hours preceding the upper gastrointestinal endoscopy, with a 2-hour complete fast, including for liquids
Other: 24-Hour Clear Liquid Diet
Standard Fasting
Standard pre-procedural fasting according to current recommendations: the patient keeps a standard fasting prior to the upper gastrointestinal endoscopy, with a 6-hour fast for solid food and 2-hour fast for liquids
Other: Standard Fasting
24-Hour Clear Liquid Diet OTHER
24-hour clear liquid diet prior to upper gastrointestinal endoscopy with a 2-hour complete fast, including for liquids
Standard Fasting OTHER
Standard fasting prior to upper gastrointestinal endoscopy, of 6-hours for solid foods and 2 hours for liquids
What researchers are measuring
Outcome measures describe what is being studied. They are not proof that a treatment works.
Primary measures
Incidence of Retained Gastric Content
Time frame: During the index upper gastrointestinal endoscopy (Day 0)
Proportion of patients with clinically significant retained gastric content, defined as a GRACE (Gastroscopy RAte of Cleanliness Evaluation) stomach score of 0 (solid food precluding visualization of the underlying mucosa), compared with GRACE stomach scores of 1, 2 or 3. The GRACE stomach score ranges from 0 to 3; higher scores indicate better mucosal cleanliness.
Secondary measures
Procedure interruption rate due to retained gastric content and risk of aspiration
Time frame: Day 0
Not reported in this registry record.
Peri-procedural adverse events (aspiration, SpO₂ <90%, emergent advanced airway)
Time frame: Day 0
Not reported in this registry record.
Inadequate visualization rate (GRACE stomach 0-1 vs 2-3)
Time frame: Day 0
Percentage of participants with a Gastroscopy RAte of Cleanliness Evaluation (GRACE) stomach score of 0 or 1, compared with scores of 2 or 3. The GRACE stomach score ranges from 0 to 3; higher scores indicate better mucosal cleanliness.
Optimal visualization rate (GRACE stomach 3 vs 0-2)
Time frame: Day 0
Percentage of participants with a Gastroscopy RAte of Cleanliness Evaluation (GRACE) stomach score of 3, compared with scores of 0, 1 or 2. The GRACE stomach score ranges from 0 to 3; higher scores indicate better mucosal cleanliness.
Gastric lesion detection rate
Time frame: Up to 4 weeks
Gastric lesion detection rate defined as the detection of any subepithelial lesion, extensive intestinal metaplasia, dysplasia, carcinoma, neuroendocrine tumour, or lymphoma.
Peri-procedural hypoglycemia (capillary glucose <70 mg/dL), before and after the procedure
Time frame: Day 0
Not reported in this registry record.
Other measures
Total GRACE score
Time frame: Day 0
Gastroscopy RAte of Cleanliness Evaluation (GRACE) Total Score Sum of the esophagus, stomach and duodenum GRACE scores; Range 0 to 9; higher scores indicate better mucosal cleanliness.
GRACE esophagus score
Time frame: Day 0
Gastroscopy RAte of Cleanliness Evaluation (GRACE) Esophagus Score; Range 0 to 3; higher scores indicate better mucosal cleanliness.
GRACE stomach score
Time frame: Day 0
Gastroscopy RAte of Cleanliness Evaluation (GRACE) Stomach Score; Range 0 to 3; higher scores indicate better mucosal cleanliness.
GRACE duodenum score
Time frame: Day 0
Gastroscopy RAte of Cleanliness Evaluation (GRACE) Duodenum Score; Range 0 to 3; higher scores indicate better mucosal cleanliness
Review the complete result tables and limitations in the official record.
Open official results ↗Research locations (1)
The overall study status and a local site’s status can differ. Confirm that location’s availability before traveling.
1 locations
Portuguese Oncology Institute of CoimbraCoimbra, PortugalStatus unknown
Study team and timeline
- Lead sponsor
- Portuguese Oncology Institute, Coimbra
- Study start
- 2027-01 Estimated
- Primary completion
- 2027-12 Estimated
- Study completion
- 2027-12 Estimated
- First posted
- Nov 10, 2026 Actual
- Last updated
- Nov 10, 2026 Actual
Official study contacts
Official study title
24-hour Clear Liquid Diet vs. Standard Fasting for Upper Gastrointestinal Endoscopy in Patients Taking Agonists of the GLP-1 Receptor (CLEAR-GLP1 Trial): a Randomized, Parallel-group, Multicentre, International Clinical Trial
Ask Wellness Clinical Research
Your message goes to WCR, including when this study is run by another organization. WCR may offer general guidance but may not operate this trial, have access to its team or be able to enroll you.
Source: ClinicalTrials.gov API v2. Information is submitted by sponsors and investigators. NLM does not approve the safety or science of all listed studies. Registry disclaimer.
Retrieved: Nov 12, 2026 · Last registry update: Nov 10, 2026