OverweightNCT06325722
Diet Order Effects of Low Fat vs. Low Carb Diets on Body Fat Change
A study testing Low-carbohydrate Diet and Low-fat Diet in people with Overweight and Obesity, run by National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) at 1 site in United States.
Trial summary
Background: In a previous study, participants were lived at the NIH and randomly received either a low-fat or a low-carbohydrate diet for 2 weeks and then switched to the other diet for 2 more weeks. Read more about this study
- Who is it for?
- Ages 18 to 50 years
- Conditions the study is for
- Overweight, Obesity
- What is being tested?
- Low-carbohydrate Diet and Low-fat Diet
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 42 participants
- Where
- 1 siteUnited States
- Study dates
- 28 Aug 2024to 30 Nov 2029
- 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 50 years
- All sexes
- No healthy volunteers
- Adult
Who may be able to join
- In order to be eligible to participate in this study, an individual must meet all of the following criteria:
- Stated willingness to comply with all study procedures and availability for the duration of the study
- Adults aged 18-50 years
- Weight stable (< +/- 5% over past 6 months) as determined by volunteer report
- Body mass index (BMI) >= 25 kg/m^2
- Agreement to adhere to Lifestyle Considerations throughout the study duration
Who cannot join
- Subjects with cardiac pacemakers or other implants that may be affected by or affect the DXA measurements
- Inadequate access to equipment required for the study (e.g., too little refrigerator storage space or a microwave oven that is too small) as determined by discretion of PI and/or study team
- Evidence of diseases or conditions that may influence appetite (e.g., cancer, diabetes, alterations of smell or taste post COVID-19), diseases or conditions that affect the immune system, or other conditions at the discretion of the PI and/or study team
- Taking prescription medications or other drugs that may influence metabolism (including but not limited to diet/weight-loss medication, some psychiatric medications, or other medications at the discretion of the PI and/or study team)
- People unlikely to adhere to a relatively consistent daily and weekly routine and avoid travel during their participation in the study. For example, people with occupations such as pilots, flight attendants, or frequently travel for work or pleasure.
- People unlikely to abstain from off study food or supplements that may impact metabolism or appetite at the discretion of the study team
Show all 17Show fewer
- Positive pregnancy test or lactating as determined by volunteer report (women only)
- Inability or unwillingness to use birth control between screening and completion of the study (women only)
- Symptoms or signs of perimenopause or menopause by volunteer report (women only)
- Regular vigorous exercise >150 min per week as determined by volunteer report
- Alcohol consumption > 3 drinks per day as determined by volunteer report
- Regular use of tobacco (smoking, chewing, or vaping), nicotine replacement therapy, or illicit drugs over past 6 months as determined by volunteer report. Subjects may also be excluded based on a urine drug test.
- Psychological conditions as determined by DSM-5 Self-rated Level 1 Cross-cutting Symptom Measure such as (but not limited to) eating disorders, depression, bipolar disorders, that would be incompatible with safe and successful participation in this study, as determined by investigators
- Volunteers with strict dietary concerns (e.g. vegetarian or kosher diet, food allergies) or a reported dislike of a significant fraction of the study foods
- Volunteers unwilling or unable to give informed consent
- Non-English speakers due to unavailability of required questionnaires in other languages
- Resting Energy Expenditure test result within 10% of the 2500 calorie requirement at rest
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
National Institutes of Health Clinical Center
Bethesda, Maryland, 20892
Valerie Darcey, 301-402-9689, valerie.darcey@nih.gov
About this study
Background:
In a previous study, participants were lived at the NIH and randomly received either a low-fat or a low-carbohydrate diet for 2 weeks and then switched to the other diet for 2 more weeks. Participants who received the low-carbohydrate diet first lost more body fat at the end of the study than those who received the low-fat diet first. Researchers want to see if they can repeat that result in a longer weight loss study when participants live at home.
Read more
Objective:
To test the effects of diet order in people receiving either a low-fat or low-carbohydrate diet first for 4 weeks and then immediately switched to the other diet for another 4 weeks.
Eligibility:
Adults aged 19 to 50 years with a body mass index of 25 or more.
Design:
Participants will complete the study at their homes, but there will be 3 required visits to the NIH. Participants will drink a special type of water 2 weeks before the baseline NIH visit and collect urine samples at home to measure how many calories they burn. Before the diets begin, participants will visit the NIH for baseline testing when they will have a metabolism test while relaxing in a bed with a plastic hood over their head to collect the air they breathe out. They will have scans to measure their bone density and how much muscle and body fat they have. They will give stool, blood, and urine samples.
Participants will be asked to eat a specific diet for 4 weeks followed by a different diet for 4 weeks. All meals will be delivered to the participants' homes. They will eat only the foods delivered.
Participants will weigh themselves daily. They will wear a monitor to track their physical activity and a sensor to measure their glucose levels. They will prick their finger each morning to test a drop of blood for ketones. Participants will meet virtually as a group with the study team weekly. Participants will have two more NIH visits towards the end of each diet period....
Read the detailed description
Study Description:
This is an 8-week crossover outpatient feeding trial of a low carbohydrate versus a low-fat diet, each provided for 4 weeks in random order with no washout period, in adult volunteers with overweight or obesity.
Objectives:
Primary Objectives: To determine the effect of diet order on the mean total fat mass change in subjects randomized to receive either a low carbohydrate followed by a low fat diet or the reverse order, with each diet lasting for 4 weeks.
Secondary Objectives: To determine the effect of diet order on the mean rate of body weight change in subjects randomized to receive either a low carbohydrate followed by a low fat diet or the reverse order, with each diet lasting for 4 weeks and the rate of weight change is measured during the last 2 weeks of each diet. To determine the effect of diet order on mean total body weight change in subjects randomized to receive either a low carbohydrate followed by a low fat diet or the reverse order, with each diet lasting for 4 weeks.
Endpoints:
Primary Endpoint: Mean total fat mass change measured by dual energy X-ray absorptiometry at baseline and week 8.
Secondary Endpoints: Mean rate of weight change by linear mixed modeling of daily weight measurements. Mean total body weight change measured between baseline and week 8.
- Conditions
- Overweight, Obesity
- Being tested
- Low-carbohydrate Diet, Low-fat Diet
- Keywords
- Diet, Body Fat, Nutrition, weight-loss
- Medical subject headings
- Overweight, Obesity, Weight Loss
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Low-carbohydrate DietOther
Consisting of 15 percent protein, 75 percent fat, and 10 percent carbohydrate
Low-fat DietOther
Consisting of 15 percent protein, 10 percent fat, and 75 percent carbohydrate
| Study group | Role | What they receive |
|---|---|---|
| low-carbohydrate diet then low-fat diet | Experimental | A low-carbohydrate followed by low-fat diet, each lasting for 4 weeks in adults with overweight or obesity Receives: Other: Low-carbohydrate Diet; Other: Low-fat Diet |
| low-fat diet then low-carbohydrate diet | Experimental | A low-fat followed by low-carbohydrate diet, each lasting for 4 weeks in adults with overweight or obesity Receives: Other: Low-carbohydrate Diet; Other: Low-fat Diet |
What is being measured
The primary outcome is the main question the study is designed to answer.
Change in total fat mass
Change in total fat mass (kg) as measured by dual energy X-ray absorptiometry (DXA) from baseline to week 8
Measured: 8 weeks
Secondary outcomes (3)
Rate of body weight change from baseline to week 8
Rate of body weight change (kg/d) from baseline to week 8
Measured: 8 weeks
Rate of body weight change during low-carbohydrate diet
Rate of body weight change (kg/d) during the last two weeks of the low-carbohydrate diet
Measured: Last 2 weeks of low-carbohydrate diet period
Rate of body weight change during low-fat diet
Rate of body weight change (kg/d) during the last two weeks of the low-fat diet
Measured: Last 2 weeks of low-fat diet period
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted22 Mar 2024
- Study start28 Aug 2024
- Primary completion30 Nov 2029 (estimated)
- Study completion30 Nov 2029 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (2)Papers the sponsor has linked to this study.
- Other trials for OverweightStudies of the same condition, open and under way.
- More trials run by National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)The 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
- Basic science
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Single blind
- Who is masked
- Participant
- Enrolment
- 42 participants (estimated)
Sponsor and investigators
- Sponsor type
- US National Institutes of Health
- Responsible party
- Sponsor
- Investigators
- Valerie L Darcey, Principal investigator, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06325722
- Sponsor's protocol ID
- 10001680
- Other IDs
- 001680-DK
- Status last verified
- 29 Oct 2026
- First submitted
- 21 Mar 2024
- Last updated
- 2 Nov 2026
- Results posted
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Yes: Body fat and body weight data
Publications
Sciarrillo CM, Guo J, Hengist A, Darcey VL, Hall KD. Diet order affects energy balance in randomized crossover feeding studies that vary in macronutrients but not ultra-processing. medRxiv [Preprint]. 2023 Oct 4:2023.10.03.23296501. doi: 10.1101/2023.10.03.23296501.
PubMed 37986904Hall KD, Guo J, Courville AB, Boring J, Brychta R, Chen KY, Darcey V, Forde CG, Gharib AM, Gallagher I, Howard R, Joseph PV, Milley L, Ouwerkerk R, Raisinger K, Rozga I, Schick A, Stagliano M, Torres S, Walter M, Walter P, Yang S, Chung ST. Effect of a plant-based, low-fat diet versus an animal-based, ketogenic diet on ad libitum energy intake. Nat Med. 2021 Feb;27(2):344-353. doi: 10.1038/s41591-020-01209-1. Epub 2021 Jan 21.
PubMed 33479499
Study at a glance
From the registry record, last updated by the sponsor on 2 Nov 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Diet Order Effects of Low Fat vs. Low Carb Diets on Body Fat Change
- ClinicalTrials.gov ID
- NCT06325722
- Acronym / sponsor ID
- 10001680
- Conditions
- Overweight, Obesity
- Keywords
- Diet, Body Fat, Nutrition, weight-loss
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 42 participants (estimated)
- Lead sponsor
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)US National Institutes of Health
- Study start
- 28 Aug 2024 (actual)
- Primary completion
- 30 Nov 2029 (estimated)
- Study completion
- 30 Nov 2029 (estimated)
- First posted
- 22 Mar 2024 (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.
Background:
In a previous study, participants were lived at the NIH and randomly received either a low-fat or a low-carbohydrate diet for 2 weeks and then switched to the other diet for 2 more weeks. Participants who received the low-carbohydrate diet first lost more body fat at the end of the study than those who received the low-fat diet first. Researchers want to see if they can repeat that result in a longer weight loss study when participants live at home.
Objective:
To test the effects of diet order in people receiving either a low-fat or low-carbohydrate diet first for 4 weeks and then immediately switched to the other diet for another 4 weeks.
Eligibility:
Adults aged 19 to 50 years with a body mass index of 25 or more.
Design:
Participants will complete the study at their homes, but there will be 3 required visits to the NIH. Participants will drink a special type of water 2 weeks before the baseline NIH visit and collect urine samples at home to measure how many calories they burn. Before the diets begin, participants will visit the NIH for baseline testing when they will have a metabolism test while relaxing in a bed with a plastic hood over their head to collect the air they breathe out. They will have scans to measure their bone density and how much muscle and body fat they have. They will give stool, blood, and urine samples.
Participants will be asked to eat a specific diet for 4 weeks followed by a different diet for 4 weeks. All meals will be delivered to the participants' homes. They will eat only the foods delivered.
Participants will weigh themselves daily. They will wear a monitor to track their physical activity and a sensor to measure their glucose levels. They will prick their finger each morning to test a drop of blood for ketones. Participants will meet virtually as a group with the study team weekly. Participants will have two more NIH visits towards the end of each diet period....
Detailed description
Study Description:
This is an 8-week crossover outpatient feeding trial of a low carbohydrate versus a low-fat diet, each provided for 4 weeks in random order with no washout period, in adult volunteers with overweight or obesity.
Objectives:
Primary Objectives: To determine the effect of diet order on the mean total fat mass change in subjects randomized to receive either a low carbohydrate followed by a low fat diet or the reverse order, with each diet lasting for 4 weeks.
Secondary Objectives: To determine the effect of diet order on the mean rate of body weight change in subjects randomized to receive either a low carbohydrate followed by a low fat diet or the reverse order, with each diet lasting for 4 weeks and the rate of weight change is measured during the last 2 weeks of each diet. To determine the effect of diet order on mean total body weight change in subjects randomized to receive either a low carbohydrate followed by a low fat diet or the reverse order, with each diet lasting for 4 weeks.
Endpoints:
Primary Endpoint: Mean total fat mass change measured by dual energy X-ray absorptiometry at baseline and week 8.
Secondary Endpoints: Mean rate of weight change by linear mixed modeling of daily weight measurements. Mean total body weight change measured between baseline and week 8.
Study design
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Single blind (participant)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| low-carbohydrate diet then low-fat diet | Experimental | Other: Low-carbohydrate Diet, Other: Low-fat DietA low-carbohydrate followed by low-fat diet, each lasting for 4 weeks in adults with overweight or obesity |
| low-fat diet then low-carbohydrate diet | Experimental | Other: Low-carbohydrate Diet, Other: Low-fat DietA low-fat followed by low-carbohydrate diet, each lasting for 4 weeks in adults with overweight or obesity |
Who may qualify
- Ages
- 18 to 50 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult
Key inclusion criteria (6 listed)
- In order to be eligible to participate in this study, an individual must meet all of the following criteria:
- Stated willingness to comply with all study procedures and availability for the duration of the study
- Adults aged 18-50 years
- Weight stable (< +/- 5% over past 6 months) as determined by volunteer report
- Body mass index (BMI) >= 25 kg/m^2
Key exclusion criteria (17 listed)
- Subjects with cardiac pacemakers or other implants that may be affected by or affect the DXA measurements
- Inadequate access to equipment required for the study (e.g., too little refrigerator storage space or a microwave oven that is too small) as determined by discretion of PI and/or study team
- Evidence of diseases or conditions that may influence appetite (e.g., cancer, diabetes, alterations of smell or taste post COVID-19), diseases or conditions that affect the immune system, or other conditions at the discretion of the PI and/or study team
- Taking prescription medications or other drugs that may influence metabolism (including but not limited to diet/weight-loss medication, some psychiatric medications, or other medications at the discretion of the PI and/or study team)
- People unlikely to adhere to a relatively consistent daily and weekly routine and avoid travel during their participation in the study. For example, people with occupations such as pilots, flight attendants, or frequently travel for work or pleasure.
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 |
|---|---|---|
| Low-carbohydrate DietConsisting of 15 percent protein, 75 percent fat, and 10 percent carbohydrate | Other | low-carbohydrate diet then low-fat diet, low-fat diet then low-carbohydrate diet |
| Low-fat DietConsisting of 15 percent protein, 10 percent fat, and 75 percent carbohydrate | Other | low-carbohydrate diet then low-fat diet, low-fat diet then low-carbohydrate diet |
Primary outcome
Change in total fat mass
Time frame: 8 weeks
Change in total fat mass (kg) as measured by dual energy X-ray absorptiometry (DXA) from baseline to week 8
3 secondary outcomes
Rate of body weight change from baseline to week 8
Time frame: 8 weeks
Rate of body weight change during low-carbohydrate diet
Time frame: Last 2 weeks of low-carbohydrate diet period
Rate of body weight change during low-fat diet
Time frame: Last 2 weeks of low-fat diet period
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 2 Nov 2026.
- Background: PubMed 37986904Sciarrillo CM, Guo J, Hengist A, Darcey VL, Hall KD. Diet order affects energy balance in randomized crossover feeding studies that vary in macronutrients but not ultra-processing. medRxiv [Preprint]. 2023 Oct 4:2023.10.03.23296501. doi: 10.1101/2023.10.03.23296501.
- Background: PubMed 33479499Hall KD, Guo J, Courville AB, Boring J, Brychta R, Chen KY, Darcey V, Forde CG, Gharib AM, Gallagher I, Howard R, Joseph PV, Milley L, Ouwerkerk R, Raisinger K, Rozga I, Schick A, Stagliano M, Torres S, Walter M, Walter P, Yang S, Chung ST. Effect of a plant-based, low-fat diet versus an animal-based, ketogenic diet on ad libitum energy intake. Nat Med. 2021 Feb;27(2):344-353. doi: 10.1038/s41591-020-01209-1. Epub 2021 Jan 21.
- NIH Clinical Center Detailed Web PageLink provided by the sponsor.
- Individual participant dataSharing planned: Yes. Body fat and body weight data
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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.
Valerie L Darcey principal investigator
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Low-carbohydrate Diet and Low-fat Diet in people with Overweight and Obesity, run by National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) 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 6 inclusion and 17 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 2 Nov 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 Nan Zhai, C.R.N.P. ((301) 827-3324, nan.zhai@nih.gov), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Change in total fat mass (time frame: 8 weeks). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT06325722, which also lists 2 linked publications.
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 2 Nov 2026.