Ketogenic Diet Treatment of Obesity With Co-morbid Type 2 Diabetes Mellitus and/or Obstructive Sleep Apnea

Inclusion Criteria: * age 18-70 * ability and willingness to signed informed consent form * BMI more than 30kg/m2, with type 2 DM and/or OSA * For diabetic participants, stable hypoglycemic medications for at least 2 months * For participants with OSA, previously documented polysomnogram with apnea/hypopnea index (AHI)\>15/h. Exclusion Criteria: * BMI change of +/- 3.0 kg/m2 of baseline BMI within past 12 months. * History of bariatric surgery ≤ 3 years prior to enrollment. * Any systemic illness or unstable medical condition that might pose additional risk, including: cardiac, unstable metabolic or endocrine disturbances, renal or liver disease, past history of renal calculi, hyperuricemia, hypercalcemia, mitochondrial disease, known disorder of fatty acid metabolism, porphyria, and active systemic cancer. * History of uncontrolled hyperlipidemia * For participants with DM, change in the dose or type of hypoglycemic treatment within 2 months prior to enrollment. * Psychosis within six months of enrollment, evidenced by treatment with anti-psychotic medications with recent medication initiation or dose increase. * Active drug or alcohol dependence or any other factors that, in the opinion of the site investigators would interfere with adherence to study requirements; * History of hyperthyroidism * History of glaucoma * History of cerebrovascular disease or unstable heart disease within 6 months of enrollment * Pregnancy * Use of any investigational drugs within 3 months of enrollment. * Inability or unwillingness of subject to give written informed consent.