Research Studies

Age 18-40 years; Body Mass Index 18.5-<40 kg/m2 ; Recreationally active: defined as >100 minutes per week of voluntary exercise at moderate intensity or greater and >60 min per day of total habitual physical activity (i.e., work related, transportation related) at moderate intensity or greater, over the past 3 months; No self-report of acute or chronic disease (cardiovascular disease (CVD), diabetes, pulmonary, gastrointestinal disorders, and orthopedic problems in particular); No plans to relocate within the next 6 months; No plans for extended travel (>2 weeks) within the next 6 months; Live or work within 30 minutes of the AHWC (exceptions may be made at the discretion of the Study PI on a case-by-case basis for highly motivated subjects); No contraindications to exercise or limitations on ability to be physically active; Willing not to enroll in any other formal weight loss or physical activity programs over the next 6 months; For Females: Not currently pregnant or lactating, Not pregnant within the past 6 months.

Inclusion Criteria: - Age 18-40 years - Body Mass Index 18.5-<40 kg/m2 - Recreationally active: defined as >100 minutes per week of voluntary exercise at moderate intensity or greater and >60 min per day of total habitual physical activity (i.e., work related, transportation related) at moderate intensity or greater, over the past 3 months. - No self-report of acute or chronic disease (cardiovascular disease (CVD), diabetes, pulmonary, gastrointestinal disorders, and orthopedic problems in particular). - No plans to relocate within the next 6 months. - No plans for extended travel (>2 weeks) within the next 6 months. - Live or work within 30 minutes of the AHWC (exceptions may be made at the discretion of the Study PI on a case-by-case basis for highly motivated subjects). - Capable and willing to give informed consent, understand exclusion criteria, and adhere to study conditions. - Have a primary care physician (or are willing to establish care with a primary care physician prior to study enrollment) to address medical issues which may arise during screening or study procedures. - No contraindications to exercise or limitations on ability to be physically active. - Ability to complete AM or PM exercise and complete 4 exercise sessions per week. - Ability to adhere to eating and exercise protocols (meal timing, exercising in fasted and fed states) - Willing and able to wear activity/sleep monitor for 7 consecutive days. - Willing not to enroll in any other formal weight loss or physical activity programs over the next 6 months. - For Females: Not currently pregnant or lactating. Not pregnant within the past 6 months. Not planning to become pregnant in the next 6 months Exclusion Criteria: - Diastolic blood pressure >100 mmHG, systolic blood pressure >160 mmHG, or resting heart rate >100 bpm - Diabetes - Undiagnosed hypo- or hyper-thyroidism or history of uncontrolled thyroid disorder. History of thyroid disease or current thyroid disease treated with a stable medication regimen for at least 6 months is acceptable. - Hematocrit, white blood cell count or platelets significantly outside the normal reference range. - Triglycerides >400 mg/dL - LDL cholesterol >200 mg/dL - Abnormal resting electrocardiogram (ECG) - Presence or history of any metabolic or chronic health problems which would affect appetite, food intake, energy metabolism, or ability to participate in exercise - Significant gastrointestinal disorders - Significant pulmonary disorders including - Symptoms suggestive of CVD - Regular use of prescription or over-the-counter medications known to significantly impact appetite, weight, or energy metabolism - Use of medications that would impact ability to achieve age-predicted maximum heart rate (e.g. beta blockers). - Regular use of systemic steroids. - Regular use of weight loss drugs within the last 6 months. - Current alcohol or substance abuse. - Nicotine use (past 6 months). - Current severe depression or history of severe depression within the previous year - History of significant psychiatric illness (e.g., psychosis, schizophrenia, mania, bipolar disorder) - Weight loss >5% in past 3 months. - Currently participating in or planning to participate in any formal weight loss or physical activity programs or clinical trials. - Sleep disorders like insomnia, obstructive sleep apnea, periodic limb movements in sleep, restless leg syndrome. - Night-time shiftwork, rotating work, or other circadian disruptions and disorders - Self-reported long (>9.25h) or short sleep (<7h) - Regular use of prescription or over-the-counter medications known to affect sleep - Regular use of melatonin (>/=2 days per week). - High consumption of caffeine (>500 mg/d) or unwilling to abstain from caffeine consumption during run-in and in-patient protocol. - Planned travel >1 time zone away 4 weeks prior to study start or at any time during study protocol.