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): 18.0-65.0,  Obesity Weight Loss Obese: BMI> 30 kg/m2 or >27 kg/m2 with comorbidities (including but not limited to insulin resistance, hypertension, dyslipidemia, cardiovascular disease, stroke, sleep apnea, gallbladder disease, hyperuricemia and gout, and osteoarthritis). Additionally, women participants must use double barrier methods to prevent pregnancy (diaphragm with intravaginal spermicide, cervical cap, male or female condom with spermicide). If a woman suspects that she has become pregnant at any time or does not use one of the contraceptive methods recommended by the investigator, she must notify the study staff. If a woman becomes pregnant, she will be withdrawn from the study. The study staff will follow the progress of her pregnancy and the birth of her child  Subjects using any other weight loss products (orlistat, phentermine, topiramate, fenfluramine, dexfenfluramine, amphetamines, GLP-1 agonists) or use within 3 months. 2. Women who are breastfeeding, pregnant, or wanting to become pregnant. 3. Women using IUD (intrauterine device) 4. Any change in the dosage of hormonal contraceptive medications (birth control pills, implanon). Subjects should remain on same medication/ same dose during the time of the entire study. 5. Moderate (creatinine clearance of 30-59 ml/min) and severe renal impairment (creatinine clearance below 30 ml/min) and end-stage renal disease 6. Moderate, or severe hepatic impairment 7. Hypersensitivity to the active substance or any of the excipients in lorcaserin 8. Congestive heart failure and/or pulmonary hypertension 9. Arrhythmias (bradycardia, tachycardia) and valvular heart diseases 10. Diagnosis of diabetes, defined per ADA as Hba1c > 6.5% and/or fasting glucose > 125 mg/dL and/or random glucose > 200 mg/dL 11. Inflammatory conditions like inflammatory bowel disease, Rheumatoid arthritis etc. 12. Alcohol consumption the maximum quantity for men is 140g-210g per week. For women, the range is 84g-140g per week or drinking as consuming no more than two drinks a day for men and one for women. Alcohol can cause increased risk of pancreatitis and hypoglycemia. 13. Untreated thyroid disease like hypothyroidism or hyperthyroidism 14. Subjects taking the following medications: phosphodiesterase inhibitors, serotonergic medications (e.g. SSRI (selective serotonin reuptake inhibitor), SNRI, MAO (monoamine oxidase) inhibitors, bupropion, tricyclic antidepressants, St. John's Wort), valproic acid, codeine (CYP2D6 inhibition), tamoxifen, timolol, warfarin, steroids (inhaled or systemic due to reduced hypoglycemic effect), and subjects on other hormones (LHRH analogs etc). 15. Subjects with any type of bioimplant activated by mechanical, electronic, or magnetic means (e.g. cochlear implants, pacemakers, neuron or biostimulators, electronic infusion pumps, etc.) 16. Subjects with any type of metallic implant that could potentially be displaced or damaged during MRI, such as aneurysm clips, metallic skull plates, surgical implants etc. or metal containing tattoos 17. Anxiety of small spaces and/or claustrophobia 18. Uncontrolled cardiac impairment, circulatory impairment, or inability to perspire (poor thermoregulatory function) 19. Significant sensory or motor impairment 20. Epilepsy, particularly photo-sensitive epilepsy, which may place the individual at a higher risk for adverse events during fMRI scanning with visual stimulation 21. Subjects with neurological problems which may interfere with or complicate testing (e.g. presence of titubation) 22. Body weight above the limitation of the MRI scanning table (330lbs/150 Kg) or body dimensions that could difficult the performance of the scan. 23. Subjects who cannot adhere to the experimental protocol for any reason 24. Anemia with Hgb less than 10 25. Uncontrolled infectious diseases (e.g. HIV, hepatitis, chronic infections etc) 26. Any uncontrolled endocrine condition, e.g. Cushing's, Acromegaly, etc 27. Any cancers or lymphoma 28. Eating disorders like anorexia, bulimia 29. Weight loss surgery or gastrectomy