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

the study will be conducted following different periods:

• Free diet (for 4 weeks). After recruitment, the patient will enter "free diet phase" in which he/she will be asked to follow a normal free diet for 4 weeks. During this period, a nutritional interview will be carried out by a trained dietician who will elaborate a personalized diet and order the ketogenic products on the basis of patient's preferences.
• very low calories ketogenic diet (for 8 weeks). After the free diet period, the patient will start the very low calories ketogenic regimen. At the beginning of this period a box with the commercial products necessary to cover the whole study period will be hand-delivered by a dietician that will instruct the patient on the correct use and storage.
• Maintenance (for 12 weeks). After very low calories ketogenic diet phase, the patient will start maintenance period as described

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