Physical InactivityNCT05147909
Impact of Dietary Phosphate Excess on Exercise Capacity and Visceral Adiposity
A study testing Sodium Phosphate and Sodium Chloride in people with Physical Inactivity and Phosphate Overload, run by University of Texas Southwestern Medical Center at 1 site in United States.
Trial summary
Studies in mice demonstrated that dietary phosphate (Pi) loading that mimic the level of US adult consumption leads to reduced spontaneous locomotor activity, exercise capacity, and reduced resting metabolic rate when in normal mice by impairing skeletal muscle mitochondrial function and fat oxidation. Read more about this study
- Who is it for?
- Ages 18 to 80 yearsHealthy volunteers can take part
- Conditions the study is for
- Physical Inactivity, Phosphate Overload, Visceral Obesity
- What is being tested?
- Sodium Phosphate and Sodium Chloride
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 124 participants
- Where
- 1 siteUnited States
- Study dates
- 14 Sep 2022to 30 Mar 2028
- 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 80 years
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- The randomized crossover trial will be performed in on otherwise healthy subjects without diabetes mellitus, chronic kidney disease (CKD), preexisting cardiovascular disease or treatment with any vasoactive agent that might alter cardiovascular responses to exercise.
Who cannot join
- history of cardiopulmonary disease or chronic kidney disease,
- treatment with antihypertensive medications,
- estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73m2, (4) diabetes mellitus or other systemic illness,
- pregnancy, (6) hypersensitivity to sodium phosphate, (7) any history of substance abuse or current cigarette use, (8) any history of psychiatric illness, (9) history of active malignancy, (10) serum phosphorus < 2.4 or > 4.5 mg/dL.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United States1 site, 1 recruiting
- Recruiting
University of Texas Southwestern
Dallas, Texas, 75209
John Giacona, PA-C
About this study
Studies in mice demonstrated that dietary phosphate (Pi) loading that mimic the level of US adult consumption leads to reduced spontaneous locomotor activity, exercise capacity, and reduced resting metabolic rate when in normal mice by impairing skeletal muscle mitochondrial function and fat oxidation. However, relevance of this findings in humans remains unknown.
Read the detailed description
The investigators will perform a randomized, crossover study to determine if lowering dietary Pi intake from 1,200 mg/day to recommended daily allowance (RDA) of 700 mg/day increases skeletal muscle ATP synthesis, raises exercise oxygen uptake (VO2) during cardiopulmonary testing. To ensure stable Pi intake prior to randomization, Pi consumption will be estimated by food recall during a run-in and washout phase for 2 consecutive days, using the Automated Self-Administered 24-Hour (ASA24®) Dietary Assessment Tool (https://epi.grants.cancer.gov/asa24/). After the run-in period, all participants will be maintained on a low Pi diet (700 mg/d) and a normal Na diet of approximately 3,128 mg/d throughout the study for 8 weeks. Subjects will also be randomized to receive Sodium Phosphate 2 capsules daily (containing a total of 500 mg of Pi, 372mg of sodium) for 4 weeks during the high Pi phase (total Pi intake 1,200 mg/d) vs 2 capsules of Sodium Chloride (NaCl, containing a total of 372mg of sodium) to match Na content to Sodium Phosphate without extra Pi daily for 4 weeks during the low Pi phase (total Pi intake = 700 mg/d). The total Na intake during the entire study will be at usual US consumption level of 3,500 mg/d. Investigational drug service at UT Southwestern will dispense Sodium Phosphate vs. NaCl tablets and the study subjects will be blinded to the type of supplement they receive.
During the periods of high and low Pi phases, the investigators will monitor 24-hr urinary Pi excretion (UPiV) to ensure adherence. Since approximately 70% of ingested Pi is absorbed and excreted in the urine, we expect 24-hr UPiV excretion to be approximately 840 mg during the high Pi phase and 490 mg during the low Pi phase. If 24-hr UPiV is < 800 mg during the high Pi diet or > 500 mg during the low Pi diet, the research dietitian will provide additional counseling to improve adherence to the menu plan. If needed, the research diet will be altered to be more compatible with the participant's preference.
24-hr urinary Pi, Na, K, Cr, and Ca excretion will be assessed after weeks 2 and 4 of the low and high Pi phases. Serum electrolytes and Pi will be monitored every 2 weeks. Serum FGF23, and soluble Klotho levels and cardiopulmonary testing and P31 MRS of quadriceps muscle will be obtained after 4 weeks on the study diet. The order of study supplement will be randomized. Subsequently, participants will stop the first study supplement and undergo washout for 2 weeks. After 2 weeks of washout, they will receive the 2nd study supplement. Measurement of skeletal muscle ATP synthesis and VO2 at rest and during exercise will be repeated in the same fashion.
- Conditions
- Physical Inactivity, Phosphate Overload, Visceral Obesity
- Being tested
- Sodium Phosphate, Sodium Chloride
- Medical subject headings
- Sedentary Behavior, Obesity, Abdominal
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Sodium PhosphateDietary supplement
Also called NaPO4
Sodium Phosphate 2 capsules daily (containing a total of 500 mg of Pi, 372mg of sodium)
Sodium ChlorideDietary supplement
Also called NaCl
Sodium Chloride 2 capsules daily (NaCl, containing a total of 372mg of sodium)
| Study group | Role | What they receive |
|---|---|---|
| Sodium Phosphate (NaPO4) then sodium chloride (NaCl) | Experimental | Participants will be asked to take 2 capsules daily of Sodium Phosphate (containing a total of 500 mg of Pi, 372mg of sodium) ) for 4 weeks during the high Pi phase (total Pi intake 1,200 mg/d). Then, participants will be asked to take 2 capsules of Sodium Chloride (NaCl, containing a total of 372mg of sodium) to match Na content to Sodium Phosphate without extra Pi daily for 4 weeks during the low Pi phase (total Pi intake = 700 mg/d). Receives: Dietary Supplement: Sodium Phosphate; Dietary Supplement: Sodium Chloride |
| NaCl then NaPO4 | Experimental | Participants will be asked to take 2 capsules daily of Sodium Chloride (NaCl, containing a total of 372mg of sodium) for 4 weeks during the low Pi phase (total Pi intake = 700 mg/d). Then, participants will be asked to take 2 capsules of Sodium Phosphate daily for 4 weeks Sodium Phosphate (containing a total of 500 mg of Pi, 372mg of sodium) for 4 weeks during the high Pi phase (total Pi intake 1,200 mg/d). Receives: Dietary Supplement: Sodium Phosphate; Dietary Supplement: Sodium Chloride |
What is being measured
The primary outcome is the main question the study is designed to answer.
oxygen uptake (VO2) during peak exercise
VO2 (ml of oxygen consumed /min) will be measured using a metabolic cart (Medgraphics) during exercise in a stationary bicycle. Standard breath-by-breath respiratory gases (VO2) will be measured at rest and after 3 minutes of steady state exercise at both 20 and 40 Watts using a cycle ergometer (Lode). Then, the partcipants will be asked to perform exercise to maximal level to obtain peak VO2.
Measured: 4 weeks
Secondary outcomes (4)
Resting ATP synthesis
Resting ATP synthesis (mM/min) will be measured using a magnetic resonance spectroscopy (MRS). The rate of exchange of high energy phosphates between phosphocreatine and ATP will be used to calculate resting ATP synthesis.
Measured: 4 weeks
Phosphocreatine (PCr) depletion
PCr depletion (%) will be measured in the calf muscle after measurements of resting ATP synthesis by MRS. Participants will be asked to perform plantar flexion exercise for 1 min of foot-pushing against a magnet-compatible pulley system mounted on the scanner table constant workload (20% of estimated lean body weight at 2 s/cycle, 1 second of contraction/1 second of relaxation). Two bouts of exercise are performed by each subject with 10 min recovery between each bout and the results are averaged.
Measured: 4 weeks
submaximal VO2
VO2 (ml of oxygen consumed /min) will be measured using a metabolic cart (Medgraphics) during exercise in a stationary bicycle. Standard breath-by-breath respiratory gases (VO2) will be measured at rest and after 3 minutes of steady state exercise at both 20 and 40 Watts using a cycle ergometer (Lode) to obtain levels of sub maximal oxygen uptake
Measured: 4 weeks
Cardiac output (CO)
CO (ml/min) will be measured at rest and during the same stationary bicycle exercise while VO2 is monitored, using an inert gas rebreathing method. The Innocor rebreathing system (Innovision A/S, Odense, Denmark) uses a combination of both an inert soluble gas (0.5% nitrous oxide) and an inert insoluble gas (0.1% sulfur hexafluoride) and has been shown to provide a reliable assessment of lung volumes and cardiac output non-invasively.
Measured: 4 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted7 Dec 2021
- Study start14 Sep 2022
- Primary completion31 Mar 2027 (estimated)
- Study completion30 Mar 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Physical InactivityStudies of the same condition, open and under way.
- More trials run by University of Texas Southwestern Medical CenterThe sponsor's other registered studies.
- 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
- Prevention
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Double blind
- Who is masked
- Participant, Investigator
- Enrolment
- 124 participants (estimated)
Sponsor and investigators
- Lead sponsor
- University of Texas Southwestern Medical Center
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Wanpen Vongpatanasin, University of Texas Southwestern Medical Center
- Investigators
- Wanpen Vongpatanasin, MD, Principal investigator, Wanpen.Vongpatanasin@UTSouthwestern.edu
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05147909
- Sponsor's protocol ID
- STU-2021-1068
- Status last verified
- Feb 2026
- First submitted
- 23 Nov 2021
- Last updated
- 17 Feb 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Yes: We will share de-identified data upon reasonable request.
Study at a glance
From the registry record, last updated by the sponsor on 17 Feb 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Impact of Dietary Phosphate Excess on Exercise Capacity and Visceral Adiposity
- ClinicalTrials.gov ID
- NCT05147909
- Acronym / sponsor ID
- STU-2021-1068
- Conditions
- Physical Inactivity, Phosphate Overload, Visceral Obesity
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 124 participants (estimated)
- Lead sponsor
- University of Texas Southwestern Medical CenterUniversity, hospital or other
- Study start
- 14 Sep 2022 (actual)
- Primary completion
- 31 Mar 2027 (estimated)
- Study completion
- 30 Mar 2028 (estimated)
- First posted
- 7 Dec 2021 (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.
Studies in mice demonstrated that dietary phosphate (Pi) loading that mimic the level of US adult consumption leads to reduced spontaneous locomotor activity, exercise capacity, and reduced resting metabolic rate when in normal mice by impairing skeletal muscle mitochondrial function and fat oxidation. However, relevance of this findings in humans remains unknown.
Detailed description
The investigators will perform a randomized, crossover study to determine if lowering dietary Pi intake from 1,200 mg/day to recommended daily allowance (RDA) of 700 mg/day increases skeletal muscle ATP synthesis, raises exercise oxygen uptake (VO2) during cardiopulmonary testing. To ensure stable Pi intake prior to randomization, Pi consumption will be estimated by food recall during a run-in and washout phase for 2 consecutive days, using the Automated Self-Administered 24-Hour (ASA24®) Dietary Assessment Tool (https://epi.grants.cancer.gov/asa24/). After the run-in period, all participants will be maintained on a low Pi diet (700 mg/d) and a normal Na diet of approximately 3,128 mg/d throughout the study for 8 weeks. Subjects will also be randomized to receive Sodium Phosphate 2 capsules daily (containing a total of 500 mg of Pi, 372mg of sodium) for 4 weeks during the high Pi phase (total Pi intake 1,200 mg/d) vs 2 capsules of Sodium Chloride (NaCl, containing a total of 372mg of sodium) to match Na content to Sodium Phosphate without extra Pi daily for 4 weeks during the low Pi phase (total Pi intake = 700 mg/d). The total Na intake during the entire study will be at usual US consumption level of 3,500 mg/d. Investigational drug service at UT Southwestern will dispense Sodium Phosphate vs. NaCl tablets and the study subjects will be blinded to the type of supplement they receive.
During the periods of high and low Pi phases, the investigators will monitor 24-hr urinary Pi excretion (UPiV) to ensure adherence. Since approximately 70% of ingested Pi is absorbed and excreted in the urine, we expect 24-hr UPiV excretion to be approximately 840 mg during the high Pi phase and 490 mg during the low Pi phase. If 24-hr UPiV is < 800 mg during the high Pi diet or > 500 mg during the low Pi diet, the research dietitian will provide additional counseling to improve adherence to the menu plan. If needed, the research diet will be altered to be more compatible with the participant's preference.
24-hr urinary Pi, Na, K, Cr, and Ca excretion will be assessed after weeks 2 and 4 of the low and high Pi phases. Serum electrolytes and Pi will be monitored every 2 weeks. Serum FGF23, and soluble Klotho levels and cardiopulmonary testing and P31 MRS of quadriceps muscle will be obtained after 4 weeks on the study diet. The order of study supplement will be randomized. Subsequently, participants will stop the first study supplement and undergo washout for 2 weeks. After 2 weeks of washout, they will receive the 2nd study supplement. Measurement of skeletal muscle ATP synthesis and VO2 at rest and during exercise will be repeated in the same fashion.
Study design
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Double blind (participant, investigator)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Sodium Phosphate (NaPO4) then sodium chloride (NaCl) | Experimental | Dietary Supplement: Sodium Phosphate, Dietary Supplement: Sodium ChlorideParticipants will be asked to take 2 capsules daily of Sodium Phosphate (containing a total of 500 mg of Pi, 372mg of sodium) ) for 4 weeks during the high Pi phase (total Pi intake 1,200 mg/d). Then, participants will be asked to take 2 capsules of Sodium Chloride (NaCl, containing a total of 372mg of sodium) to match Na content to Sodium Phosphate without extra Pi daily for 4 weeks during the low Pi phase (total Pi intake = 700 mg/d). |
| NaCl then NaPO4 | Experimental | Dietary Supplement: Sodium Phosphate, Dietary Supplement: Sodium ChlorideParticipants will be asked to take 2 capsules daily of Sodium Chloride (NaCl, containing a total of 372mg of sodium) for 4 weeks during the low Pi phase (total Pi intake = 700 mg/d). Then, participants will be asked to take 2 capsules of Sodium Phosphate daily for 4 weeks Sodium Phosphate (containing a total of 500 mg of Pi, 372mg of sodium) for 4 weeks during the high Pi phase (total Pi intake 1,200 mg/d). |
Who may qualify
- Ages
- 18 to 80 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (1 listed)
- The randomized crossover trial will be performed in on otherwise healthy subjects without diabetes mellitus, chronic kidney disease (CKD), preexisting cardiovascular disease or treatment with any vasoactive agent that might alter cardiovascular responses to exercise.
Key exclusion criteria (4 listed)
- history of cardiopulmonary disease or chronic kidney disease,
- treatment with antihypertensive medications,
- estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73m2, (4) diabetes mellitus or other systemic illness,
- pregnancy, (6) hypersensitivity to sodium phosphate, (7) any history of substance abuse or current cigarette use, (8) any history of psychiatric illness, (9) history of active malignancy, (10) serum phosphorus < 2.4 or > 4.5 mg/dL.
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 |
|---|---|---|
| Sodium PhosphateAlso: NaPO4Sodium Phosphate 2 capsules daily (containing a total of 500 mg of Pi, 372mg of sodium) | Dietary supplement | NaCl then NaPO4, Sodium Phosphate (NaPO4) then sodium chloride (NaCl) |
| Sodium ChlorideAlso: NaClSodium Chloride 2 capsules daily (NaCl, containing a total of 372mg of sodium) | Dietary supplement | NaCl then NaPO4, Sodium Phosphate (NaPO4) then sodium chloride (NaCl) |
Primary outcome
oxygen uptake (VO2) during peak exercise
Time frame: 4 weeks
VO2 (ml of oxygen consumed /min) will be measured using a metabolic cart (Medgraphics) during exercise in a stationary bicycle. Standard breath-by-breath respiratory gases (VO2) will be measured at rest and after 3 minutes of steady state exercise at both 20 and 40 Watts using a cycle ergometer (Lode). Then, the partcipants will be asked to perform exercise to maximal level to obtain peak VO2.
4 secondary outcomes
Resting ATP synthesis
Time frame: 4 weeks
Phosphocreatine (PCr) depletion
Time frame: 4 weeks
submaximal VO2
Time frame: 4 weeks
Cardiac output (CO)
Time frame: 4 weeks
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 17 Feb 2026.
- Individual participant dataSharing planned: Yes. We will share de-identified data upon reasonable request.
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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.
Wanpen Vongpatanasin, MD principal investigator
Wanpen.Vongpatanasin@UTSouthwestern.edu
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Sodium Phosphate and Sodium Chloride in people with Physical Inactivity and Phosphate Overload, run by University of Texas Southwestern Medical Center at 1 site in United States.
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 1 inclusion and 4 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: looking for participants now, as of the sponsor's last update on 17 Feb 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 United States. 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?
Contact John Giacona, PA-C (2146484403, john.giacona@utsouthwestern.edu), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
oxygen uptake (VO2) during peak exercise (time frame: 4 weeks). 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 17 Feb 2026.