Effect of Weight Loss on Urinary Oxalate Excretion in Obese Calcium Oxalate Kidney Stone Formers

August 28, 2026 updated by: Dean Assimos, MD, University of Alabama at Birmingham

Effect of Weight Loss on Urinary Oxalate Excretion in Obese Calcium Oxalate Kidney Stone

This protocol seeks to determine if weight reduction with the Optifast VLCD program leads to reduced contribution of endogenous oxalate synthesis and dietary oxalate absorption to the urinary oxalate pool in obese calcium oxalate stone formers.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Active, not recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

Obese adults (≥19 and ≤ 65 years) with a history of calcium oxalate kidney stone disease will be recruited at both University of Alabama at Birmingham (UAB) and University of Texas South Western (UTSW). Following consent, subjects will complete a screening phase, which includes (1) a meeting with a dietitian to ensure willingness to consume controlled ultra-low oxalate diets and determine anthropometric measurements and blood pressure, (2) collection of fasted blood and 2 x 24-hour urine specimens on self-choice diets to determine general health status and urinary chemistries, respectively, (3) completion of a 7-day run-in diet that includes the use of one serving of an Optifast meal daily to assess tolerance to Optifast VLCD® products. Participants will then consume an eucaloric, ultra-low oxalate controlled diet for 6 days. The controlled dietary phase involves 2 days of dietary equilibration, followed by 2 x 24-hour urine collections, and on the 5th day a dietary oxalate/sucralose oral load. Following the dietary oxalate/sucralose oral load, subjects will have blood collected every 30 minutes and collect 1-hour urines. Participants will then go on an intensive 14-week Optifast VLCD® Program to induce weight loss. At the end of this Optifast VLCD® Program participants will again perform the low oxalate controlled diet and dietary/sucralose oral load study. A total of 40 adult obese calcium oxalate kidney stone formers (20 male and 20 female) will be enrolled (20 at UAB and 20 at UTSW).

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
14

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

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

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

  • United States
    • Alabama
      • Birmingham, Alabama, United States, 35243
        • University of Alabama at Birmingham

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

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

19 years to 65 years (Adult, Older Adult)

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • First time or recurrent calcium oxalate stone formers defined as composition of most recent stone >50% calcium oxalate without uric acid component
  • Last stone passage or removal greater than 3 months prior to screening
  • Body Mass Index (BMI) >35 kg/m2
  • Able to provide consent
  • Hemoglobin A1C <6.5%
  • Normal fasting blood CMP: Normal serum Na, K, Cl, CO2, Calcium, Albumin, AST, ALT <2 times upper limit of normal, Glucose <126 mg/dl, eGFR >60 ml/min/1.73 m2.
  • 24-hour urine collection with creatinine within 20% of gender appropriate (mg creat/kg body weight) and consistent between collections (within 20% of each other)
  • Willing to ingest menus prepared at the University of Alabama and University of Texas Southwestern Clinical Research Units
  • Willing to consume the Optifast VLCD diet
  • Willing to ingest menus prepared in Metabolic kitchen. No food allergies or intolerance to any of the foods in study menus. Substitutions for lactose intolerance will be made.
  • Willing to avoid vigorous exercise during eucaloric, low-oxalate dietary phase
  • Willing to stop use of weight-loss medications
  • Willing to stop for 14 days before and during study: medications for stone prevention including diuretics, potassium citrate, allopurinol, febuxostat, and calcium, nutritional, or herbal supplements
  • Those with controlled hypertension (systolic blood pressure <160 mmHg, diastolic <90 mmHg) will be included.
  • Those without severe dyslipidemia (LDL <200 mg/dL, HDL >30 mg/dL, and triglycerides <250 mg/dL) will be included. Treated and controlled dyslipidemia is accepted
  • Smoking/chewing tobacco/vaping will be allowed

Exclusion Criteria:

  • Renal colic or past stone surgery in the past 3 months
  • Estimated Glomerular Filtration Rate (eGFR) less than 60 ml/min/1.73m2
  • History of type 2 diabetes or screening hgb A1c greater than or equal to 6.5%
  • Alcohol or drug abuse. Alcohol consumption >12 units per week and/or unwillingness to abstain from alcohol consumption 2 days before and during the study.
  • Mental/medical condition likely to impede study completion
  • Current/planned pregnancy or breastfeeding in coming 6 months, unwillingness to use effective method of birth control during the study for individuals of childbearing potential.
  • Planned vacation in coming 4 months
  • Febrile illness including flu/common cold/COVID-19 within 21 days of study start
  • Primary or enteric hyperoxaluria
  • Gastrointestinal disorder or surgery that impacts oxalate transport
  • Cirrhosis, pancreatic or biliary disorder, porphyria, gout
  • Malignancy treated within the past 12 months
  • Nephrotic syndrome, neurogenic bladder, urinary diversion
  • History of primary hyperparathyroidism, cystinuria, renal tubular acidosis, sarcoidosis, cystic fibrosis
  • Uncontrolled hypertension, myocardial infarction in past 6 months, unstable angina, congestive heart failure
  • Medications: Topiramate, acetazolamide, zonisamide, diuretics, SGLT2-inhibitors, immunosuppressants

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

  • Primary Purpose: Basic Science
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Controlled Diet and Weight Loss Program
Subjects will consume a low oxalate diet with blood and urine collections to establish baseline levels before undergoing a weight loss program with Optifast VLCD products. After completing the weight loss program, subjects will once again consume a low oxalate diet with blood and urine collections to observe any changes that may have occurred due to the weight loss.
Dietary supplement: Low Oxalate Diet before Weight Loss
Subjects will be instructed to ingest a controlled diet low in oxalate for a total of 6 days. 2 x 24 hour urines will be collected on days 3 and 4.
Dietary supplement: Optifast VLCD Program
Subjects will go on a 10-week Intestive level Optifast VLCD weight loss program
Dietary supplement: Optifast VLCD Transition Phase
After completion of the 10-week Optifast VLCD Program, subjects will be weaned off the Optifast products for 4 weeks.
Dietary supplement: Low Oxalate Diet after Weight Loss
Subjects will be instructed to ingest a controlled diet low in oxalate for a total of 11 days and collect 2 x 24 hour urines on days 8 and 9
Dietary supplement: Oral load of oxalate and sucralose before Weight Loss
Subjects will ingest 100mg carbon-13 oxalate, and 1 gram of sucralose on day 5 of the 6-day low oxalate diet phase. Following the oral load, blood and urine will be collected every 30 minutes and hourly, respectively
Dietary supplement: Oral load of oxalate and sucralose after Weight Loss
Subjects will ingest 100mg carbon-13 oxalate, and 1 gram of sucralose on day 10 of the 11-day low oxalate diet phase. Following the oral load, blood and urine will be collected every 30 minutes and hourly, respectively

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Measurement of 24 hour urinary oxalate excretion
Time Frame: 4 days
Subjects will ingest a controlled diet low in oxalate and collect 2 x 24-hour urines before and after the Optifast VLCD Program. The utilization of a low oxalate diet allows assessment of the change in contribution of endogenous oxalate synthesis to the urinary oxalate pool.
4 days

Collaborators and Investigators

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

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
University of Alabama at Birmingham

Collaborators

Collaborators

An organization other than the sponsor that provides support for a clinical study. This support may include activities related to funding, design, implementation, data analysis, or reporting.
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
University of Texas Southwestern Medical Center

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Principal Investigator: Dean Assimos, MD, University of Alabama at Birmingham

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)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
December 3, 2021

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
December 31, 2025

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
December 31, 2026

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
November 11, 2020

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
November 11, 2020

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
November 18, 2020

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
September 1, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
August 28, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
March 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • IRB-300006133
  • R01DK128160 (U.S. NIH Grant/Contract)

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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