An interventional study of Low-carbohydrate Diet and Low-fat Diet in Overweight and Obesity, sponsored by National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Recruiting at 1 site in United States. Open to participants aged 18 Years to 50 Years. Per ClinicalTrials.gov, last updated 2026-11-02.
Sponsored by National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) · Not applicable, Interventional, and Basic science
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....
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.
11,522 studies on the registry are indexed under Obesity; 2,033 are open to participants now.
This study's planned enrollment of 42 is below the median of 67 across 9,006 interventional studies indexed under Obesity.
Browse Obesity studies →National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) is the lead sponsor of 538 studies on the registry; 55 are open to participants now.
Of its 80 completed or terminated interventional studies of FDA-regulated products, 51 (64%) have results posted.
Compared within Obesity, this study's primary condition as ClinicalTrials.gg classifies it; the registry's first condition term is Overweight. The counts are of registry records indexed under each term, refreshed daily. How we classify →
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
In order to be eligible to participate in this study, an individual must meet all of the following criteria:
EXCLUSION CRITERIA:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
The American Psychiatric Association’s manual of mental health diagnoses. DSM-5 (2013, revised as DSM-5-TR in 2022) replaced DSM-IV, and some studies still name the older edition. “Meets DSM criteria for …” means diagnosed by that edition’s diagnostic criteria, usually by a clinician in an interview.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
DSM diagnostic criteria
The American Psychiatric Association’s manual of mental health diagnoses. DSM-5 (2013, revised as DSM-5-TR in 2022) replaced DSM-IV, and some studies still name the older edition. “Meets DSM criteria for …” means diagnosed by that edition’s diagnostic criteria, usually by a clinician in an interview.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
A low-carbohydrate followed by low-fat diet, each lasting for 4 weeks in adults with overweight or obesity
Other: Low-carbohydrate Diet · Other: Low-fat Diet
A low-fat followed by low-carbohydrate diet, each lasting for 4 weeks in adults with overweight or obesity
Other: Low-carbohydrate Diet · Other: Low-fat Diet
Consisting of 15 percent protein, 75 percent fat, and 10 percent carbohydrate
Consisting of 15 percent protein, 10 percent fat, and 75 percent carbohydrate
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
Time frame: 8 weeks
Rate of body weight change from baseline to week 8
Rate of body weight change (kg/d) from baseline to week 8
Time frame: 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
Time frame: 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
Time frame: Last 2 weeks of low-fat diet period
Plan to share: Yes — Body fat and body weight data
Supporting information: Study protocol, Analytic code
Time frame: Upon publication in peer reviewed journal
Access criteria: Open, general access
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) →