The goal of this clinical trial is to learn if the time an individual eats each day impacts neurological health in people with multiple sclerosis. The main questions the investigators are asking are:

1. Does meal timing affect biomarkers of neuronal health (neurofilament light chain [NfL] and BDNF) and inflammation (IL-6, IL-17, TNF-ɑ) in adults with MS.
2. Does meal timing affect expression of circadian clock genes and genes associated with autophagy in adults with MS.

Participants will be instructed to start and stop eating at specific times each day based on their group assignment and their personal schedule. They will respond to prompts sent to them on their smartphone to record the times they start and stop eating each day.

As a secondary goal, the study will also explore the feasibility of including translocator protein (TSPO)-PET imaging of neuroinflammation in future clinical trials of TRE in people with MS. To accomplish this, imaging will be completed in a subset of 8 participants at the beginning and end of the study.

The mechanisms underlying the relationship between diet and MS are not well understood. A leading theory is that diet affects disease progression and symptoms through modulation of neuroinflammation. Previous studies in participants with other conditions suggest that time restricted eating (TRE) may reduce inflammation by improving circadian rhythms. If this holds true in people with MS, it may explain how TRE improves clinical outcomes of cognitive and physical function as seen in a previous trial. It may also explain diurnal fluctuations in pain and fatigue experienced by people within MS.

Although a previous study measured the effect of TRE on physical and cognitive function, as well as pain and fatigue, it was a single arm study and did not measure the hypothesized mechanisms of action. Therefore, the purpose of this pilot study is to examine the effects of TRE on neurological, inflammatory, and circadian markers in adults with MS.

Adults with relapsing forms of MS (relapsing remitting [RRMS] or secondary progressive [SPMS], n = 22) will be randomly assigned to either a TRE group that will eat all food within an 8-hour window each day (treatment group) or a group that will eat over 12 or more hours each day for 12 weeks.

Further, investigators will assess the feasibility of using Positron Emission Tomography (PET) imaging to measure changes in neuroinflammation with TRE. This exploratory aim will be completed in a subset of participants (n=8), and will be used to finalize imaging protocols and determine feasibility of including translocator protein (TSPO)-PET imaging of neuroinflammation in future clinical trials of TRE in people with MS.

Inclusion Criteria:

• Diagnosed with relapsing remitting or secondary progressive multiple sclerosis (RRMS or SPMS)
• If on disease modifying therapy (DMTs), stable for 6 months
• If not on DMTs, no DMT usage within previous 6 months
• BMI 18.5-50 kg/m2
• Access to a smartphone
• Responsible for personal eating schedule or able to have input into schedule

Exclusion Criteria:

• Relapse within previous 30 days
• Actively engaged in a weight loss program or unwilling to follow assigned eating schedule
• Current use of GLP-1 or use within previous 3 months
• Regularly fasts > 12 hours/day
• Employed in night shift or rotating shift work
• Unable to walk 25 feet with or without assistive device (EDSS > 6.5).
• Current use of insulin or sulfonylurea agents
• Pregnant or breastfeeding
• Currently enrolled in another trial that would confound results (e.g., exercise studies or other diet studies)