Actively Recruiting
Diet Order Effects of Low Fat vs. Low Carb Diets on Body Fat Change
Led by National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) · Updated on 2026-05-12
42
Participants Needed
1
Research Sites
100 weeks
Total Duration
On this page
AI-Summary
What this Trial 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. 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....
CONDITIONS
Official Title
Diet Order Effects of Low Fat vs. Low Carb Diets on Body Fat Change
Who Can Participate
Eligibility Criteria
You may qualify if you...
- Willingness to follow all study procedures and be available for the entire study duration
- Adults aged 18 to 50 years
- Weight stable within plus or minus 5 percent over the past 6 months
- Body mass index (BMI) of 25 kg/m2 or higher
- Agreement to follow lifestyle considerations throughout the study
You will not qualify if you...
- Having a cardiac pacemaker or other implants that could affect bone density measurements
- Inadequate access to required equipment such as sufficient refrigerator or microwave space
- Diseases or conditions affecting appetite or the immune system, including cancer, diabetes, or taste/smell changes after COVID-19
- Taking prescription medications that influence metabolism, including diet or weight-loss drugs or some psychiatric medications
- Occupations or lifestyles involving frequent travel or inconsistent daily routines
- Unable to avoid off-study foods or supplements that affect metabolism or appetite
- Positive pregnancy test or lactating (women only)
- Inability or unwillingness to use birth control during the study (women only)
- Symptoms of perimenopause or menopause (women only)
- Regular vigorous exercise over 150 minutes per week
- Consuming more than 3 alcoholic drinks per day
- Regular use of tobacco, nicotine replacement, or illicit drugs in the past 6 months
- Psychological conditions such as eating disorders, depression, or bipolar disorder that interfere with study participation
- Strict dietary restrictions like vegetarian or kosher diets or dislike of many study foods
- Unwilling or unable to give informed consent
- Non-English speakers due to unavailable questionnaires
AI-Screening
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Trial Site Locations
Total: 1 location
1
National Institutes of Health Clinical Center
Bethesda, Maryland, United States, 20892
Actively Recruiting
Research Team
N
Nan Zhai, C.R.N.P.
CONTACT
V
Valerie L Darcey
CONTACT
How is the study designed?
Study Type
INTERVENTIONAL
Masking
SINGLE
Allocation
RANDOMIZED
Model
CROSSOVER
Primary Purpose
BASIC_SCIENCE
Number of Arms
2
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