Scientists hunt for Muscle's secret Fat-Burning signals

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: Applicable to all Groups * Healthy men and women, aged 18 - 40, inclusive. * Willing to stop alcohol and caffeine consumption for 48 hours preceding each blood draw Applicable to Group 1 * BMI between 22 and 29.9 kg/m2 * Not involved in regular exercise program * Willing to exercise every day for the study period Applicable to Group 2 * BMI between 22 and 29.9 kg/m2 * Maximal oxygen uptake (VO2max) ≥ 45 ml/kg fat-free mass /min * Engaged in a minimum of 1.5 h of moderate to vigorous intensity aerobic exercise 3 times/ week Applicable to Group 3 * BMI ≥ 30 kg/m2 and weight ≤ 350 lbs * Not involved in a regular exercise program Exclusion Criteria: Applicable to All Groups * History of Type 2 Diabetes * "Unfavorable anatomy" for continuous venous blood sample collection * Abnormal resting ECG * Significant renal, cardiac, liver, lung, or neurological disease (controlled hypertension is acceptable if baseline bp \< 140/90 on medications) * Use of drugs known to affect energy metabolism or body weight: including, but not limited to: orlistat, sibutramine, ephedrine, phenylpropanolamine, corticosterone, etc * Current treatment with blood thinners or anti-platelet medications that cannot be safely stopped for testing procedures * New onset (\<3 months on a stable regime) use of oral contraceptives or hormone replacement therapy * Alcohol or other drug abuse * Smoking within the past 3 months * Females that are currently or have been pregnant or are currently or have nursed a child within the last 12 months (minimum). * Parental enrollment into the study that compromises the well being of the child \[no partner or connected caregiver\] * Unwilling or unable to abstain from caffeine or alcohol 48 hours prior to metabolic rate measurements * Increased liver function tests * Metal objects that would interfere with the measurement of body composition /magnetic resonance spectroscopy such as implanted rods, surgical clips, etc * Any New York Heart Association class of congestive heart failure * History of deep vein thrombosis or pulmonary embolism * Significant varicose veins * Abnormal blood count/Anemia, or blood donation within the last 2 months * Major surgery on the abdomen, pelvis, or lower extremities within previous 3 months * Bariatric surgery or liposuction within the previous 3 years * Cancer (active malignancy with or without concurrent chemotherapy) * Rheumatoid disease * Bypass graft in limb * Known genetic factor (Factor V Leiden, etc) or hypercoagulable state * Diagnosed peripheral arterial or vascular disease, or intermittent claudication * Family history of primary deep vein thrombosis or pulmonary embolism * Peripheral neuropathy * Claustrophobia * Frequent nocturnal urination and/or sleep apnea * Presence of any condition that, in the opinion of the investigator, compromises participant safety or data integrity or the participants' ability to complete the training protocol Applicable to Group 2 * Gait problems * Major Depression * Presence of an eating disorder or eating attitudes/behaviors that could interfere with the study completion * Unwilling or unable to complete the protocol Applicable to Group 3 * HbA1c ≥ 6.5% (O)