Diet Order Effects of Low Fat vs. Low Carb Diets on Body Fat Change
This study examines how the order in which you follow different diets affects body fat loss. Participants will eat either a low-fat or low-carbohydrate diet for 2 weeks, then switch to the other diet for another 2 weeks while living at the NIH clinical center. Previous research found that people who started with the low-carbohydrate diet lost more body fat overall.
Key Objective: This trial tests whether starting with a low-carbohydrate diet leads to greater body fat loss compared to starting with a low-fat diet.
Who to Consider: Overweight individuals interested in understanding which diet approach may be more effective for losing body fat should consider enrolling in this study.
Trial Parameters
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....
Eligibility Criteria
* INCLUSION CRITERIA: In order to be eligible to participate in this study, an individual must meet all of the following criteria: 1. Stated willingness to comply with all study procedures and availability for the duration of the study 2. Adults aged 18-50 years 3. Weight stable (\< +/- 5 percent over past 6 months) as determined by volunteer report 4. Body mass index (BMI) \>= 25 kg/m\^2 5. Agreement to adhere to Lifestyle Considerations throughout the study duration EXCLUSION CRITERIA: 1. Subjects with cardiac pacemakers or other implants that may be affected by or affect the DXA measurements 2. 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 3. 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 condi