NCT06325722 · National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Diet Order Effects of Low Fat vs. Low Carb Diets on Body Fat Change
What this study is about
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.
View original scientific description
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....
Interventions
OTHER
Low-carbohydrate Diet
Consisting of 15 percent protein, 75 percent fat, and 10 percent carbohydrate
OTHER
Low-fat Diet
Consisting of 15 percent protein, 10 percent fat, and 75 percent carbohydrate
Primary outcome measures
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
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
Inclusion criteria
- 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 percent 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
Exclusion criteria
- 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
- 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
Where
- Bethesda, Maryland
Related conditions & keywords
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Jul 17, 2026 · Source of record for eligibility and locations