An interventional study of Time-Restricted Eating (TRE) and Time-Restricted Eating with Intermittent Energy Restriction (TRE+IER) in Intermittent Fasting, sponsored by University of South Alabama. Not yet recruiting. Open to participants aged 18 Years to 65 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-07-15.
Sponsored by University of South Alabama · Not applicable, Interventional, and Basic science
This study is looking at whether eating all meals within a 6-hour window each day (called Time-Restricted Eating, or TRE) can improve body composition, metabolism, heart health, and blood markers over 12 weeks. The study also wants to find out whether allowing participants to eat normally on weekends makes the diet easier to follow long-term.
Adults aged 18-65 with a BMI of 26 or higher who do not have heart disease or diabetes may be eligible. Participants will be randomly placed into one of two groups: (1) TRE every day for 12 weeks, or (2) TRE on weekdays with normal eating on weekends. All participants will visit the lab twice - once at the start and once at the end - for measurements of body fat, resting calorie burn, heart function, and blood tests. Between visits, participants will log their meals and steps at home and check in with the research team every two weeks.
This randomized, two-arm parallel study examines the effects of Timed Restricted Eating (TRE) with or without Intermittent Energy Restriction (IER) on body composition, resting energy expenditure (REE), cardiometabolic blood markers, cardiovascular modulation, psychosocial well-being, dietary adherence, and spontaneous physical activity over a 12-week intervention in adults with overweight or obesity.
Study Design and Participants Sixty adults (30 male, 30 female) aged 18-65 years with a BMI ≥26 kg/m² will be enrolled. The target sample accounts for an anticipated one-third attrition rate, yielding a final expected sample of 40 participants (20 per group), based on a power analysis using an effect size of f=0.25 and power of 0.80. Eligible participants must be weight-stable (no more than 5 kg change in the prior 3 months), physically inactive (≤150 min/week of moderate-intensity activity), free of cardiovascular disease and diabetes, and not taking medications that could influence study outcomes. Individuals with implanted electronic devices (e.g., pacemakers, ICDs) are excluded due to the use of bioimpedance spectroscopy.
Randomization Following baseline assessments, participants will be randomly assigned in a 1:1 ratio to one of two groups using sex-stratified permuted block randomization (block sizes of 2 and 4), generated a priori using the blockrand package in R.
Intervention Groups Group 1 (TRE Only): Participants restrict all calorie-containing food and beverages to a 6-hour afternoon eating window (e.g., 2-8 pm) every day for 12 weeks.
Group 2 (TRE + IER): Participants follow the same 6-hour eating window Monday-Friday, but return to unrestricted eating on weekends (Saturday-Sunday) to test whether periodic diet breaks improve long-term adherence.
Laboratory Visits (Pre- and Post-Intervention) Both visits (\~3-3.5 hours each) follow identical protocols. Participants arrive after an overnight fast of at least 8 hours, having consumed \~500 mL of water in the 1-2 hours prior, and having abstained from vigorous exercise, alcohol, and caffeine for at least 24 hours.
Body composition is assessed using the 4-compartment (4C) model - the gold standard for body composition - combining: (1) DXA for bone mineral content; (2) air displacement plethysmography (BodPod) for body volume; (3) bioimpedance spectroscopy (BIS) for total body water; and (4) a calibrated digital scale for body mass. These are combined using the Wang equation to derive fat mass, fat-free mass, and body fat percentage.
Cardiovascular modulation is assessed with the ATCOR SphygmoCor® system, capturing peripheral and central hemodynamics, arterial stiffness via carotid-femoral pulse wave velocity (applanation tonometry), and pulse wave reflection variables (AIx, AIx75, AP, SEVR, reflection magnitude).
REE is measured via indirect calorimetry using a ventilated canopy (metabolic cart) over a 30-minute supine rest period. The 5-minute window with the lowest coefficient of variation (≤5%) is used for analysis.
Venous blood is drawn from a forearm vein and sent to LabCorp for a standard metabolic panel including fasting glucose, lipid panel (total cholesterol, LDL, HDL, triglycerides), liver enzymes, and kidney function markers.
Psychosocial well-being is assessed using the validated WHOQOL-BREF questionnaire (31 items across four domains: physical health, psychological health, social relationships, and environment).
12-Week Intervention Monitoring Participants self-document the time of their first and last calorie-containing meal daily and record daily step counts from a research-grade pedometer. The research team conducts check-ins every two weeks for compliance assessment and ease-of-adherence surveys. Adverse events are monitored continuously and reported per IRB requirements.
Post-Intervention Only Relative energy balance (average daily calorie surplus or deficit over 12 weeks) will be estimated post-hoc from DXA-derived changes in fat mass and fat-free mass using previously validated equations, minimizing participant burden by eliminating the need for daily dietary recall.
333 studies on the registry are indexed under Intermittent Fasting; 99 are open to participants now.
This study's planned enrollment of 60 is above the median of 50 across 320 interventional studies indexed under Intermittent Fasting.
Browse Intermittent Fasting studies →University of South Alabama is the lead sponsor of 29 studies on the registry; 5 are open to participants now.
Of its 5 completed or terminated interventional studies of FDA-regulated products, 3 (60%) have results posted.
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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.
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.
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.
Participants restrict all calorie-containing food and beverages to a 6-hour afternoon eating window (e.g., 2-8 pm) every day for 12 weeks. Outside of this window, only water, black coffee, and plain tea are permitted.
Behavioral: Time-Restricted Eating (TRE)
Participants restrict all calorie-containing food and beverages to the same 6-hour afternoon eating window Monday through Friday. On Saturday and Sunday, participants return to their regular, unrestricted eating habits. This arm tests whether periodic weekend diet breaks improve long-term dietary adherence while maintaining a meaningful weekly calorie deficit.
Behavioral: Time-Restricted Eating with Intermittent Energy Restriction (TRE+IER)
Participants consume all calorie-containing food and beverages within a 6-hour afternoon eating window (e.g., 2-8 pm) every day for 12 weeks. Outside of this window, only non-caloric beverages (water, black coffee, plain tea) are permitted. No changes to food quality or caloric targets are prescribed.
Participants follow the same 6-hour afternoon eating window Monday through Friday. On Saturday and Sunday, participants return to their habitual, unrestricted eating pattern (ad libitum intake). This modified approach introduces periodic weekend diet breaks to assess whether reduced dietary rigidity improves long-term adherence while maintaining a clinically meaningful weekly calorie deficit.
Body Fat Percentage
Change in body fat percentage assessed via the 4-compartment (4C) model, combining DXA-derived bone mineral content, air displacement plethysmography (BodPod) body volume, bioimpedance spectroscopy (BIS) total body water, and calibrated body mass, using the Wang equation.
Time frame: Baseline and 12 weeks
No study locations are listed for this record.
Start is estimated for Jul 2026; primary completion for May 2027, 10 months later.
Of 257 non-industry interventional studies with no phase under Intermittent Fasting, half reached primary completion within 18 months of starting (the median), counting those still running; a quarter within 9 and three quarters within 34. This study's planned 10 months is below that.
Counting every sponsor, half of 263 studies reached it within 17 months; a quarter within 8 and three quarters within 34.
How these figures are worked out, and which studies are left out of them.
This study is not yet recruiting, as verified in May 2026. You cannot join it, but the record below documents what was studied.
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University of South Alabama