Diet Order Effects of Low Fat vs. Low Carb Diets on Body Fat Change

Not Applicable

Recruiting

• Conditions: Overweight; Obesity
• Interventions: Other: Low-carbohydrate Diet; Other: Low-fat Diet

• Registration Number: NCT06325722
• Lead Sponsor: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

Brief 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. 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 Timeline

• Study First Submitted: 2024-03-21
• Study First Submitted QC: 2024-03-21
• Study First Posted: 2024-03-22
• Study Start: 2024-08-28
• Status Verified: 2024-12-27
• Last Update Submitted: 2024-12-31
• Last Update Posted: 2025-01-01
• Primary Completion: 2026-07-31
• Study Completion: 2026-07-31

Recruitment & Eligibility

• Status: RECRUITING
• Sex: All
• Target Recruitment: 100

Inclusion Criteria

Not provided

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Exclusion Criteria

Not provided

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Study & Design

• Study Type: INTERVENTIONAL
• Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
low-carbohydrate diet then low-fat diet	Low-fat Diet	A 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	Low-carbohydrate Diet	A low-fat followed by low-carbohydrate diet, each lasting for 4 weeks in adults with overweight or obesity
low-carbohydrate diet then low-fat diet	Low-carbohydrate Diet	A 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	Low-fat Diet	A low-fat followed by low-carbohydrate diet, each lasting for 4 weeks in adults with overweight or obesity

Primary Outcome Measures

Name	Time	Method
Change in total fat mass	8 weeks	Change in total fat mass (kg) as measured by dual energy X-ray absorptiometry (DXA) from baseline to week 8

Secondary Outcome Measures

Name	Time	Method
Rate of body weight change from baseline to week 8	8 weeks	Rate of body weight change (kg/d) from baseline to week 8
Rate of body weight change during low-fat diet	Last 2 weeks of low-fat diet period	Rate of body weight change (kg/d) during the last two weeks of the low-fat diet
Rate of body weight change during low-carbohydrate diet	Last 2 weeks of low-carbohydrate diet period	Rate of body weight change (kg/d) during the last two weeks of the low-carbohydrate diet

Trial Locations

Locations (1)

National Institutes of Health Clinical Center; 🇺🇸 Bethesda, Maryland, United States