Bariatric SurgeryNCT04433338
The PREBA Study: Effect of Preoperative Weight Loss With a 14-day Low-calorie Diet on Surgical Procedure and Outcomes in Patients Undergoing RYGB Surgery
A study testing 14-day Low Calorie Diet in people with Bariatric Surgery and Morbid Obesity, run by Rijnstate Hospital at 1 site in Netherlands.
Trial summary
Bariatric guidelines recommend preoperative weight loss of 5% to reduce the risk of surgical complications. However, results in the literature on the improvement of surgical procedure and outcomes are still conflicting. Read more about this study
- Who is it for?
- Ages 18 to 65 years
- Conditions the study is for
- Bariatric Surgery, Morbid Obesity
- What is being tested?
- 14-day Low Calorie Diet
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 80 participants
- Where
- 1 siteNetherlands
- Study dates
- 29 Sep 2020to Jul 2027
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 65 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Undergoing primary RYGB surgery (meeting all criteria + approval of surgeon)
- Able to prepare the meal replacements at home
Who cannot join
- Undergoing another bariatric procedure than primary RYGB.
- Diabetes Mellitus
- Contraindication for the usage of Modifast meal replacements:
- Allergy or intolerance to any substance in the used meal replacements (Soy, milk, gluten, egg, peanuts, nuts and seeds)
- Veganism
- Kidney failure (GFR < 90 ml/min/1.73m2), liver failure or cardiac insufficiency
Show all 10Show fewer
- A heart attack (myocardial infarct) in the past twelve months
- Cancer
- Hypokalaemia: serum potassium level <3.4 mmol/l
- Phenylketonuria \& Porphyria
Trial locations and contacts
1 site in 1 country.
About this study
Bariatric guidelines recommend preoperative weight loss of 5% to reduce the risk of surgical complications. However, results in the literature on the improvement of surgical procedure and outcomes are still conflicting.
This study aims to evaluate the effect of preoperative weight loss by means of a 14-day low-calorie diet in bariatric patients on operative time, the ease of the Roux-en-Y gastric bypass (RYGB) procedure and long-term weight loss in a real-life experimental setting.
- Conditions
- Bariatric Surgery, Morbid Obesity
- Being tested
- 14-day Low Calorie Diet
- Keywords
- Bariatric surgery, Morbid Obesity, Weight Loss, Diet, RYGB
- Medical subject headings
- Obesity, Morbid, Weight Loss
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
14-day Low Calorie DietOther
Participants will be asked to:
- Use 4 (women) or 5 (men) Modifast meal replacements per day.
- Daily consume a minimum of 250 grams of (raw) vegetables without dressing.
- Daily consume 100 grams of lean meat/fish/meat analogues.
- Daily consume two spoons of liquid oil
- Daily drink at least 2.0 litres of water, coffee or tea without added sugar or milk, bouillon or sugar-free drinks.
| Study group | Role | What they receive |
|---|---|---|
| Intervention group | Experimental | Participants in the intervention group will follow a low-calorie diet during 14 days before undergoing surgery. The diet will consist of both meal replacements and regular foods.
For women, the diet provides ± 900 kcal, 50 grams of carbohydrates, 85 grams of protein, 30 grams of fat and 25 grams of fibres.
For men, the diet provides ± 1000 kcal, 55 grams of carbohydrates, 100 grams of protein, 30 grams of fat and 30 grams of fibres. Receives: Other: 14-day Low Calorie Diet |
| Control group | No intervention | Participants in the control group can eat according to the standard nutritional advices provided by their dietitian. These advices are intended to educate participants on the recommended eating pattern after surgery. |
What is being measured
The primary outcome is the main question the study is designed to answer.
Operative time of the RYGB procedure
Duration of the surgical procedure, retrieved from the electronic medical record
Measured: surgery
Secondary outcomes (3)
Ease of the RYGB procedure
Ten aspects of the RYGB procedure will be scored on a 5-point Likert scale. The total score can range from 10 to 50, with 10 being the easiest.
The ten aspects include:
- Exerting force on instruments (1=very low, 5= very high)
- Difficulty of moving the liver (1=very easy, 5=very difficult)
- Size of the liver (1=very small, 5= very large)
- Size of omentum (1=very small, 5= very large)
- Difficulty of approaching pouch (1=very easy, 5=very difficult)
- Accessibility of Treitz ligament (1=very easy, 5=very difficult)
- Difficulty of creating pouch (1=very easy, 5=very difficult)
- Difficulty of measuring small intestine (1=very easy, 5=very difficult)
- Difficulty of entero-entero connection (1=very easy, 5=very difficult)
- Difficulty of abdominal wall hernia repair (1=very easy, 5=very difficult)
Measured: surgery
Appearance of the patient's liver
Includes four images of the liver in different stages (1= healthy, 2= fatty liver, 3= fatty liver with inflammation, 4= liver cirrhosis). Surgeons will be asked to choose the image that best matches the appearance of the patient's liver.
Measured: surgery
Post-operative weight loss
Body weight measurements to assess weight loss after surgery
Measured: 4 weeks, 3, 6 months and 1, 2, 3, 4, 5 years after surgery
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted16 Jun 2020
- Study start29 Sep 2020
- Primary completion22 Jun 2022
- Study completionJul 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Bariatric SurgeryStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Enrolment
- 80 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Rijnstate Hospital
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Eric J Hazebroek, MD, PhD, Principal investigator, Vitalys, part of Rijnstate hospital/Wageningen University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04433338
- Sponsor's protocol ID
- NL70092.081.19
- Status last verified
- Sep 2026
- First submitted
- 12 Jun 2020
- Last updated
- 24 Sep 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 24 Sep 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- The PREBA Study: Effect of Preoperative Weight Loss With a 14-day Low-calorie Diet on Surgical Procedure and Outcomes in Patients Undergoing RYGB Surgery
- ClinicalTrials.gov ID
- NCT04433338
- Acronym / sponsor ID
- NL70092.081.19
- Conditions
- Bariatric Surgery, Morbid Obesity
- Keywords
- Bariatric surgery, Morbid Obesity, Weight Loss, Diet, RYGB
- Study type
- Interventional
- Recruitment status
- Active, not recruiting
- Enrolment
- 80 participants (estimated)
- Lead sponsor
- Rijnstate HospitalUniversity, hospital or other
- Study start
- 29 Sep 2020 (actual)
- Primary completion
- 22 Jun 2022 (actual)
- Study completion
- Jul 2027 (estimated)
- First posted
- 16 Jun 2020 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Bariatric guidelines recommend preoperative weight loss of 5% to reduce the risk of surgical complications. However, results in the literature on the improvement of surgical procedure and outcomes are still conflicting.
This study aims to evaluate the effect of preoperative weight loss by means of a 14-day low-calorie diet in bariatric patients on operative time, the ease of the Roux-en-Y gastric bypass (RYGB) procedure and long-term weight loss in a real-life experimental setting.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Intervention group | Experimental | Other: 14-day Low Calorie DietParticipants in the intervention group will follow a low-calorie diet during 14 days before undergoing surgery. The diet will consist of both meal replacements and regular foods. For women, the diet provides ± 900 kcal, 50 grams of carbohydrates, 85 grams of protein, 30 grams of fat and 25 grams of fibres. For men, the diet provides ± 1000 kcal, 55 grams of carbohydrates, 100 grams of protein, 30 grams of fat and 30 grams of fibres. |
| Control group | No intervention | –Participants in the control group can eat according to the standard nutritional advices provided by their dietitian. These advices are intended to educate participants on the recommended eating pattern after surgery. |
Who may qualify
- Ages
- 18 to 65 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (2 listed)
- Undergoing primary RYGB surgery (meeting all criteria + approval of surgeon)
- Able to prepare the meal replacements at home
Key exclusion criteria (10 listed)
- Undergoing another bariatric procedure than primary RYGB.
- Diabetes Mellitus
- Contraindication for the usage of Modifast meal replacements:
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| 14-day Low Calorie DietParticipants will be asked to: * Use 4 (women) or 5 (men) Modifast meal replacements per day. * Daily consume a minimum of 250 grams of (raw) vegetables without dressing. * Daily consume 100 grams of lean meat/fish/meat analogues. * Daily consume two spoons of liquid oil * Daily drink at least 2.0 litres of water, coffee or tea without added sugar or milk, bouillon or sugar-free drinks. | Other | Intervention group |
Primary outcome
Operative time of the RYGB procedure
Time frame: surgery
Duration of the surgical procedure, retrieved from the electronic medical record
3 secondary outcomes
Ease of the RYGB procedure
Time frame: surgery
Appearance of the patient's liver
Time frame: surgery
Post-operative weight loss
Time frame: 4 weeks, 3, 6 months and 1, 2, 3, 4, 5 years after surgery
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 24 Sep 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Eric J Hazebroek, MD, PhD principal investigator
Vitalys, part of Rijnstate hospital/Wageningen University
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing 14-day Low Calorie Diet in people with Bariatric Surgery and Morbid Obesity, run by Rijnstate Hospital at 1 site in Netherlands.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 2 inclusion and 10 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: under way, not looking for participants, as of the sponsor's last update on 24 Sep 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Netherlands. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Operative time of the RYGB procedure (time frame: surgery). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 24 Sep 2026.