This is a randomized controlled trial that will test the effects of intermittent fasting (IF) in subjects with relapsing-remitting MS (RRMS). The goal of this clinical trial is to acquire objective evidence regarding whether an IF diet has beneficial effects in MS patients.Two dietary regimens, IF and western diet, will be compared in a randomized, controlled, single-blinded 12 week trial in RRMS patients. This is a single-center study.

RRMS patients will be enrolled in a randomized, controlled, single-blinded 12 week trial in which IF will be compared to a standard western diet. Patients will be recruited at the John L. Trotter MS center and randomly assigned to either a standard western diet or an IF diet (1:1). Enrolled subjects will complete a clinical and laboratory assessment before starting the diet (baseline), at week 6 and at end of the study (week 12). The primary outcome will be leptin at week 12 measured in the peripheral blood. Secondary outcomes will be: 1) peripheral blood metabolic profiling; 2) anthropometric (body mass index and waist circumference) and total body fat measures; 3) gut microbiota richness and composition.

Inclusion Criteria:

• Diagnosis of RRMS (2010 Mc Donald criteria).
• EDSS <6.0 and disease duration ≤ 15 years.
• On an injectable therapy for MS, glatiramer acetate (GA) or beta-interferon (beta-IFN) for at least 3 months prior to the study and with no anticipated changes of the medication for the 12 week study duration.
• Age ≥18 years.
• BMI > 22 and < 35 kg/m2 with stable weight in the 3 months prior to screening.

Exclusion Criteria:

• History of any chronic disease process (excluding MS) that could interfere with interpretation of results.
• Diagnosis in the past of an eating disorder (anorexia, bulimia, or binge eating).
• Relapsing at the time of enrollment.
• On corticosteroid treatment (oral or intravenous) in the past month. Nasal corticosteroid treatments are allowed.
• Diagnosis of diabetes or at time of OGTT (fasting glucose >126 mg/dl or > 200 mg/dl at 2 hours with a load of 75 g of glucose
• History of food allergies or food intolerance that would interfere with the study.
• History of antibiotic treatment within the past 3 months prior to enrollment
• Use of anticoagulant drugs (like Warfarin or Coumadin) that need to monitor their intake of vegetables containing high levels of vitamin K.
• Currently on a special diet and not willing to stop at least one month prior to enrollment
• Currently taking omega 3/fish oil supplements and not willing to stop administration one month prior to enrollment
• Currently pregnant or plan to become pregnant within 6 months
• Current tobacco or e-cigarette smoker

IPD will not be shared with other researchers.

Outcome assessors will be blinded to the intervention because they will not know the group assignment.