Intervention: Leptin
Trial phase: Phase 2
SMILES: CSCCC(N=C(O)C(CC(=O)O)N=C(O)C(CCC(=N)O)N=C(O)C(CC(C)C)N=C(O)C(CO)N=C(O)CN=C(O)C(CCC(=N)O)N=C(O)C(N)CC(C)C)C(O)=NC(CC(C)C)C(O)=NC(Cc1c[nH]c2ccccc12)C(O)=NC(CCC(=N)O)C(O)=NC(CC(C)C)C(O)=NC(CC(=O)O)C(O)=NC(CC(C)C)C(O)=NC(CO)C(=O)N1CCCC1C(O)=NCC(O)=NC(CS)C(=O)O
Sex: All
Age groups: Adult | Older Adult
Healthy volunteers: No
Participants at risk: 24
Group description: We will start the leptin at a dose of 0.08mg/kg fat mass in men and 0.14mg/kg fat mass in women

Leptin: Hormone - daily self injections for 6 months
Eligibility criteria:
Inclusion criteria for dietary induced weight loss group:

Age 18 or older
Body mass index (pre weight loss) between 30 and 40 kg/m2.
Weight loss achieved over a period not greater than 6 months.

Exclusion criteria for dietary induced weight loss group:

Use of a very low calorie diet in the year prior to the start of the study
History of diabetes
History of any illness that may affect the concentrations of the hormones to be studied (such as anemia, infectious diseases, renal or hepatic failure, cancer, lymphoma, clinically evident hypogonadism, malabsorption or malnourishment, hypo or hyperthyroidism, hypercortisolism, alcoholism or drug abuse, eating disorders)
On medications known to affect the hormones to be measured in this study (such as glucocorticoids, anti seizure medications or thyroid hormones), or medications for weight loss.
Known history of reactions or known hypersensitivity to E. Coli derived proteins
Breast feeding, pregnant, or wanting to become pregnant during the next year
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.).
Subjects with any type of ferromagnetic bioimplant that could potentially be displaced or damaged, such as aneurysm clips, metallic skull plates, etc.
Subjects that exhibit noticeable anxiety and/or claustrophobia.
Subjects who have cardiac or known circulatory impairment, and/or the inability to perspire (poor thermoregulatory function).
Subjects who have significant sensory or motor impairment; - Subjects who suffer from epilepsy, in particular photo-sensitive epilepsy (this would be a risk for scanning with visual stimulation).
Subjects with neurological problems that might interfere or complicate testing (e.g. presence of titubation).
Subjects who cannot adhere to the experimental protocol for any reason.

Inclusion criteria for lap band surgery induced weight loss group:

Age 18 or older.
Body mass index (pre weight loss) between 30 and 40 kg/m2.
Weight loss achieved over a period not greater than 6 months.
Approved for bariatric surgery as per Beth Israel Deaconess Medical Center (BIDMC) Bariatric Clinic guidelines
Adult men and women, age 18-65
English speaking
Willing and able to take part in a multi year study involving visits and telephone interviews
Enrolled prior to bariatric surgery.

Exclusion Criteria:

Any condition that would exclude a patient from lap band surgery as listed below -
patients with untreated major depression or psychosis
binge eating disorders
current drug and alcohol abuse
severe cardiac disease with prohibitive anesthetic risks
severe coagulopathy i
inability to comply with nutritional requirements including life-long vitamin replacement.
pregnancy
Any additional condition which is not in accordance with standard of care as per Bariatric Clinic at BIDMC.
Any condition which in the opinion of the investigators makes the candidate unsuitable for participation in this study
Diabetes controlled by medication