COGNIFOOD-Changing the Carbohydrate/Fat-ratio to Prevent Cognitive Decline and Alzheimer Pathology: A Pilot Study

Inclusion Criteria: * Ability to fully understand written and verbal information regarding the study and provide signed and dated informed consent * Prodromal Alzheimer's disease, as defined by Mild Neurocognitive Disorder due to Alzheimer's disease (AD) according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) criteria, and evidence for underlying AD pathology by either: * Cerebrospinal fluid (CSF) β-amyloid 1-42/1-40x10 ratio \< 1 and/or total tau and/or phospho-tau and/or β-amyloid 42 based on local cut-offs OR * Magnetic Resonance Imaging (MRI) evidence for medial temporal lobe atrophy (MTA score 1 or higher \[mesiotemporal atrophy\]) OR * Abnormal Fludeoxyglucose F18 (FDG) Positron Imaging Tomography (PET) and/or Pittsburgh Compound-B (PiB) PET compatible with AD type changes. (When the diagnosis prodromal AD is confirmed from medical record, no cognitive testing or renewed assessment of biological AD-pathology is needed for fulfilling this criterion.) * Montreal Cognitive Assessment (MoCa) ≥20. * Availability of a study partner with sufficient contact with the participant, willing and able to give follow-up information on the participant as well as supporting the participant throughout the study. * Self-reported expected motivation and ability to prepare most weakly meals according to given instructions, with support from the study partner. * Accept plant-based food, plus food from at least one of the following categories: A. Fish; B. Meat; C. Eggs and dairy * Ability to reliably undergo a cognitive test in Swedish Exclusion Criteria: * Major Neurocognitive Disorder (dementia) according to DSM-5 * Body-mass Index (BMI) \< 18 or BMI \> 35 * Diagnosed Diabetes Mellitus. * Ongoing treatment with Metformin, Glucagon-Like Peptide 1 (GLP-1)-analog, or Sodium-Glucose Transport Protein 2 (SGLT-2)-inhibitors * Diagnosed Familial Hypercholesterolemia * Untreated or unstable Hypertension * Alcohol or Substance abuse (current or within 2 years) * A concomitant serious disease (e.g., cancer, or major psychiatric disorder or other neurological disorder than AD) as judged by study physician * Major depression or Suicidal ideations (current or within 2 years) * History of Stroke or Myocardial infarction during the last 5 years. * Subjects with brain MRI (or CT) scan clinically significant infarct, intracranial macro bleeding, mass lesion or Normal Pressure Hydrocephalus. Those subjects with an MRI scan demonstrating minimal white matter changes (Fazekas scale for white matter lesions classification of 2 or below) and up to 2 lacunar infarcts which are judged to be clinically insignificant are allowed. * Severe loss of vision or communicative ability * Conditions preventing cooperation as judged by the study physician. * Participation in any other intervention trial within 30 days (or, if applicable, 5 half-lives of the relevant drug if longer) before baseline and along the study period. * Any planned changes in cognitive enhancers (e.g., ginkgo, cholinesterase inhibitors), statins, antidepressants, sleeping pills, supplements like medium-chain triglycerides, or any medication expected to influence cognitive function. Such medications are accepted if taken on a stable dose ≥3 months prior to baseline assessment and should, if possible, remain on the same dose during the study. Unplanned changes that take place within the study do not imply exclusion but should be registered in the case report form (CRF). * Deviations from habitual diet within 1 month before study start. A carbohydrate-restricted or fat-restricted diet, as well as any time-restricted eating, is accepted as habitual diet if stable (and the participant is open to change).