Patient description: The patient is a 34-year-old obese woman who comes to the clinic with weight concerns. She is 165 cm tall, and her weight is 113 kg (BMI: 41.5). In the past, she unsuccessfully used antiobesity agents and appetite suppressants. She is complaining of sleep apnea, PCO and dissatisfaction with her body shape. She is a high-school teacher. She is married for 5 years. She doesn't use any contraceptive methods for the past 4 months and she had no prior pregnancies. She rarely exercises and movement seems to be hard for her. She is not able to complete the four-square step test in less than 15 seconds. She does not smoke or use any drugs. Her BP: 130/80, HR: 195/min and her BMI is: 41.54. Her lab results: FBS: 98 mg/dl TG: 150 mg/dl Cholesterol: 180 mg/dl LDL: 90 mg/dl HDL: 35 mg/dl She is considering a laparoscopic gastric bypass.

Clinical trial eligibility criteria: eligible ages (years): 18.0-50.0,  Healthy Healthy Volunteers Adults age 18-50 years, male and female 2. Weight stable (less than or equal to 5 % over past 6 months) as determined by volunteer report 3. Body mass index (BMI) greater that or equal to 20kg/m2 4. Body weight greater than or equal to 53 kg 5. Able to complete daily bouts of stationary cycling at a moderate rate and intensity with a HR equal to or greater than 0.3(SqrRoot) (220-age-HRrest)+HRrest but not exceeding 0.4(SqrRoot) (220-age-HRrest)+HRrest and no signs of arrhythmia  Evidence of metabolic or cardiovascular disease, or disease that may influence metabolism (e.g. cancer, diabetes, thyroid disease) 2. Taking any prescription medication or other drug that may influence metabolism (e.g. diet/weight-loss medication, asthma medication, blood pressure medication, psychiatric medications, corticosteroids, or other medications at the discretion of the PI and/or study team) 3. Positive pregnancy test or lactation as determined by volunteer report (women only) 4. Participating in a regular exercise program (> 2h/week of vigorous activity) as determined by volunteer report 5. Hematocrit <37% (women only) 6. Hematocrit < 40% (men only) 7. Caffeine consumption > 300 mg/day as determined by volunteer report 8. Regular use of alcohol (> 2 drinks per day), tobacco (smoking or chewing) amphetamines, cocaine, heroin, or marijuana over past 6 months as determined by volunteer report 9. Psychological conditions such as (but not limited to) eating disorders, claustrophobia, clinical depression, bipolar disorders, that would be incompatible with safe and successful participation in this study, as determined by investigators. 1. Past or present history of eating disorders as determined by volunteer report 2. Past or present history of claustrophobia since part of the protocol will involve being confined to a small room for whole-body indirect calorimetry and being in an MRI scanner for liver fat measures 10. Implants, devices, or foreign objects implanted in the body that interfere with the Magnetic Resonance procedures 11. Volunteers with strict dietary concerns (e.g. vegetarian or kosher diet, food allergies) 12. Volunteers unwilling or unable to give informed consent 13. Non-English speakers due to unavailability of required questionnaires in other languages