Efficacy of a Very Low Calories Ketogenic Diet in Obese Patients With Fibromyalgia or Symptomatic Knee Osteoarthritis

Inclusion Criteria: * Age \> 18 years and \< 65 years * Body mass index ≥ 30 kg/m2 * Failed to achieve weight loss with standard low-calories diet * Any of the following conditions: BMI ≥ 35 kg/m2 Past diagnosis of type 2 diabetes without β-cell failure Hypertriglyceridemia (fasting triglycerides ≥ 150 mg/dL) or taking lipid-lowering medications Hypercholesterolemia (total cholesterol \> 200 mg/dL) or taking lipid-lowering medications Past diagnosis of arterial hypertension or taking blood pressure-lowering medications Past diagnosis of non-alcoholic fatty liver disease Past diagnosis of heart failure class NYHA I-II Past history of myocardial infarction (\> 12 months), stroke/minor stroke (\> 12 months) Past diagnosis of carotid atherosclerosis Past diagnosis of polycystic ovary syndrome (PCOS) Past diagnosis of neurodegenerative disorders * Fibromyalgia classified according to 2016 Revisions to the 2010/2011 European League Against Rheumatism/ American College of Rheumatology OR * Symptomatic knee osteoarthritis Exclusion Criteria: * Age \< 18 or \> 65 years * Currently pregnant or breastfeeding * Past diagnosis of type 1 diabetes mellitus, latent autoimmune diabetes in adults, β-cell failure in type 2 diabetes mellitus, use of sodium/glucose cotransporter 2 inhibitors (risk for euglycemic diabetic ketoacidosis) * Past diagnosis of kidney failure and moderate-to-severe chronic kidney disease, liver failure, hearth failure NYHA III-IV, respiratory failure * Past diagnosis of unstable angina * Recent stroke or myocardial infarction (\< 12 months) * Cardiac arrhythmias * Past diagnosis of eating disorders and other severe mental illnesses, alcohol and substance abuse * Active/severe infections * 48 h prior to elective surgery or invasive procedures and perioperative period * Past diagnosis of rare disorders: porphyria, carnitine deficiency, carnitine palmitoyltransferase deficiency, carnitine-acylcarnitine translocase deficiency, mitochondrial fatty acid β-oxidation disorders, pyruvate carboxylase deficiency * Allergy to protein-preparations ingredients * Past or current history of gallstones