Effects of Timed Restricted Eating on Body Composition, Metabolism, and Cardiovascular Health

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.

Inclusion Criteria: * Between 18 and 65 years of age * Body mass index (BMI) of 26 kg/m² or higher (overweight or obese range) * Physically inactive, defined as 150 minutes or less of moderate-intensity physical activity per week for the 3 months prior to enrollment * No previous history of cardiovascular disease or Type 1 or Type 2 Diabetes Mellitus * Not currently taking medications that may affect blood sugar, cholesterol, or body weight (e.g., glucose-lowering drugs, statins, or weight loss medications) * Weight stable, defined as no more than 5 kg (about 11 lbs.) of body weight change in the 3 months prior to enrollment * Willing and able to follow the study requirements, provide voluntary consent, and complete all study procedures Exclusion Criteria: * Younger than 18 or older than 65 years of age * BMI below 26 kg/m² * More than 150 minutes per week of moderate-intensity physical activity in the past 3 months * History of cardiovascular disease or Type 1 or Type 2 Diabetes Mellitus * Currently taking medications that may impact study outcomes * Weight change of more than 5 kg in the past 3 months * Pregnant, breastfeeding, or planning to become pregnant during the study * History of an eating disorder * Previous weight loss surgery (e.g., gastric bypass or sleeve gastrectomy) * Unable to fast for approximately 18 hours at a time due to a medical condition * Currently working night shifts * Has a pacemaker or any implanted electronic device (due to bioimpedance spectroscopy testing) * Any health condition the research team determines would put the participant at risk