Our study aims to determine whether intermittent fasting (IMF) is a valid method to improve psoriasis and psoriatic arthritis (PsA) disease severity and quality of life. Patients within OSU Dermatology with psoriasis and/or psoriatic arthritis will be enrolled in a dietary intervention for a 24-week period. A prospective, single-blind parallel group randomized control trial will include an IMF dietary intervention group and a standard routine diet group for a duration of 24 weeks. After the initial 12 weeks of the dietary intervention, patients will be followed for an additional 12 weeks to assess changes in their disease state and quality of life after returning to their initial dietary routines. In total, the study will be 24 weeks. Baseline assessment will consist of standard psoriasis and PsA clinical parameters; evaluation will be performed by a blinded physician. These parameters will be reassessed every 4 weeks via video visit for the three month duration of the study, and then again at the 24-week conclusion of the study. In addition, each visit will assess patient-reported outcomes using dermatology-specific quality of life indices. Biometric measurements of weight, height, BMI, and waist-to-hip ratio will be recorded at baseline and all subsequent visits. Dietary adherence will be assessed by virtual check-in visits, and dietary guidance will be provided and reviewed at each visit by the research coordinator. A physician or the research coordinator will be available for questions between times of data collection. The primary outcome measure will be feasibility of a larger study, which will be determined at the initial 12-week timepoint. This data is vital to determine effect size and dropout frequency for future studies. Secondary outcomes will include changes in clinical indices, biometric measurements, and quality of life indices at 12 weeks after randomization and at the end of the 24-week study. Achievement of a 5% weight reduction at 12 weeks, and a 10-15% weight reduction at 24 weeks will be additional secondary endpoints. Data for each patient will be stored in a password-protected and encrypted REDCAP database on a secure OSU server.

Aim 1: Assess the feasibility of a larger study testing the association between intermittent fasting and disease severity in patients with psoriasis using psoriasis-specific clinical indices and patient-reported psoriasis outcomes.

The investigators will conduct a prospective, single-blind parallel group randomized control trial. Participants will be identified through an electronic medical record search for established patients within the Ohio State Dermatology practice with a diagnosis of mild-to-moderate psoriasis. Patients will then be asked to join the study and subsequently given information to consent. Patients in the control group will be offered entry into the intermittent fasting group after the commencement of the study as an incentive to participate.

Setting: The clinical setting will be the outpatient dermatology clinic sites for the Ohio State University Wexner Medical Center, Columbus, OH. The sites have access to measurement equipment, well-lit examination rooms, clinical trial support, and convenient locations for patient access.

Study Procedures: Patients will receive information regarding their dietary modifications before the start of the study; they will also be randomized to their group at this time. In the IMF group of the study, subjects will be permitted to eat food of any type and quantity for 8 hours of each day at any timing. Patients in the standard routine dietary guidance group are encouraged to continue their current diet while recording their first and last meal of the day until the first data collection. By doing this, the investigators will ensure that there is a difference in total energy consumption time between the IMF group and our controls. After the first 12 weeks of the study and subsequent data collection, patients will be permitted to resume their normal dietary habits for the remaining 12 weeks of the study.

Random Allocation: Following consent, the participants who meet the inclusion criteria will be block randomized by presence of PsA and time in a 1:1 ratio to either the IMF diet intervention or standard routine dietary guidance. Recruitment will ensure at least 20% of each group contains patients with PsA. The assessing physician investigator will be blinded to the group assignment of each patient, although the research coordinator will not be blinded. Patients cannot reasonably be blinded to their assignment. Data for each patient will be stored in a password-protected and encrypted REDCAP database on a secure OSU server. Each patient will receive a random numerical identity in the database which their data points will be associated with. Data access is role-based and limited to PI, research coordinator, statistician, and support staff.

Early stopping rules: Early stop permitted due to illness or lack of adherence; data will be included under the intention-to-treat (ITT) assumption.

Monitoring Plan: Safety monitoring will be patient-reported when patients come to clinical site and in between checkpoints if needed. Due to COVID-19, adjustments for electronic visitations will be allowable if patients can appropriately document all areas of involvement as well as take updated biometric measurements.

Aim 2: Assess the feasibility of a larger study testing the association between intermittent fasting and disease severity in patients with psoriatic arthritis using standardized DAPSA score and patient-reported outcomes

Setting: As in Aim 1, the clinical setting will be the outpatient dermatology clinic sites for the Ohio State University Wexner Medical Center, Columbus, OH. The resources and personnel at these sites are also appropriate for this aim. Design: In this aim, data points to be collected will be the DAPSA score, as well as scoring systems for enthesitis and dactylitis. Quality of life will be assessed using HRQL score.

Study Procedures: After the patient has consented, the patient will be block randomized as in Aim 1. Initial baseline assessment will be performed by a blinded physician. Baseline assessment will consist of DAPSA, enthesitis, and dactylitis indices. Health-related quality of life (HRQL) survey will be administered to patients at baseline and 12 and 24-week timepoints. All other items that are collected in Aim 1 will also be collected in this group.

All other aspects of Aim 2 not mentioned in this section are the same as in Aim 1.

Inclusion Criteria:

• 18 years of age and older
• Established patient at the clinical site with a diagnosis of mild to moderate plaque psoriasis despite treatment
• Ability to consent and follow dietary instructions
• Overweight (BMI ≥ 25)
• No change in systemic psoriasis treatment for 6 weeks

Exclusion Criteria:

• Pregnancy and/or breastfeeding
• Insulin-dependent diabetics
• Severe heart, kidney, and liver disease
• Obesity due to medical condition
• Use of medical treatment for weight reduction

Care provider and investigator are blinded to the arm, but patient has to know which diet to follow and outcomes assessor assigned the groups and has to counsel patients accordingly.