Physiological and Psychological Effects of Testosterone During Severe Energy Deficit and Recovery

Inclusion Criteria: * Physically active (at least 2 days per week aerobic and/or resistance exercise) * Not taking any prescription medications and/or willing to refrain from all medication use prior to and throughout the entire study period, unless provided/approved by the study physician * Willing to refrain from alcohol, smoking, e-cigarettes, or use of any nicotine product, caffeine, and dietary supplement use throughout the entire study period * At the discretion of the study physician, wash-out period for medications, supplements, and over-the-counter medications is ≥ 1 to 4 weeks * Wash-out period for caffeine and alcohol is ≥ 7 days * Willing to live on the Pennington Biomedical Research Center inpatient unit for 28 consecutive days * Willing to have a urine drug screening * Meets age-specific U.S. Army body composition standards according to Army Regulation 600-9, which includes estimates of percent body fat based on height, weight, and circumference measures (neck and waist) * Total testosterone concentration is within the normal physiological range, total testosterone (300-1,000 ng/dL). Exclusion Criteria: * Musculoskeletal injuries that compromise exercise capability * Diagnosed cardiometabolic disorders (i.e., hypertension, hyperlipidemia, kidney disease, diabetes, etc.) * Allergies or intolerance to foods, vegetarian practices, or history of complications with lidocaine * Anabolic steroid, human growth hormone, or nutritional testosterone precursor-like supplement use within the past 6 months * Will not refrain from smoking (any nicotine product), alcohol, caffeine, or any other dietary supplement during the study * Any use of antibiotics, except topical antibiotics, within 3 months of study participation * Colonoscopy within 3 months of study participation * Chronic use of laxatives, stool softeners, antacids, or anti-diarrheal medications (≥ once a week) * History of gastrointestinal disease (e.g., celiac, irritable bowel syndrome, colitis, Crohn's disease) * Restrained eater (the Three-Factor Eating Questionnaire) as assessed by the study's psychological and behavioral assessment staff * Adults unable to consent * Women * Prisoners * Metal implants, claustrophobia, head size incompatible with MRI equipment, etc. * Sedentary or engages in \<2 days of physical activity per week (aerobic and/or resistance training) * Exceeds age-specific U.S. Army body composition standards according to Army Regulation 600-9 * Previous history of kidney stones unless otherwise approved by the medical investigator * Systolic blood pressure \> 150 or diastolic blood pressure \> 95 mmHg * Previous history of breast or prostate cancer * Previous history of Chronic Obstructive Pulmonary Disease or Obstructive Sleep Apnea * Findings of lab results of prostate-specific antigen \> 3ng/ml, Hematocrit \> 50%, or positive urine drug screening * Based on the investigative team's clinical judgment, a subject may not be appropriate for participation in the study