The goal of this clinical trial is to investigate the impact of intermittent fasting on sleep, quality of life and fatigue among healthy volunteers. The main questions aim to answer:

Whether intermittent fasting would allow participants to experience an improvement in their sleep quality, duration and latency? Whether intermittent fasting would ameliorate participants' quality of life and reduce chronic fatigue symptoms? Researchers will compare the two most prevailing fasting windows of intermittent diet including an early morning feeding window (8 a.m.-4 p.m.) and a late feeding window (12 p.m.-8 p.m.) to see if there is a difference among these feeding windows on sleep and quality of life.

Participants will:

• Be divided into two groups (group A and group B) that will alternate their fasting windows.
• Group A will start with intermittent fasting over a feeding period from 12 p.m. to 8 p.m. for one month, then a two weeks period of usual eating habits (washout period) and finally one month of intermittent fasting with a feeding period from 8 a.m. to 4 p.m.
• Group B will follow intermittent fasting over a feeding period from 8 a.m. to 4 p.m for one month, then a two weeks period of usual eating habits (washout period) and finally one month of intermittent fasting with a feeding period from 12 p.m. to 8 p.m.
• At enrollment, at the end of each month of intermittent fasting and at the end of washout period participants will be asked to complete some questionnaires and will be submitted to anthropometric measurements using impedance scales.
• Participants will be asked to complete an electronic 24 hour recall diary using the Automated Self-Administered 24h Dietary Assessment (ASA24) Tool software once per week every week during study.

This is a randomized clinical trial focusing on the effect of intermittent fasting on sleep and quality of life among healthy population. More specifically, the first objective of this study will be to investigate the impact of intermittent fasting on sleep including sleep quality, efficiency, duration, and sleep latency among healthy individuals. The second objective will be to explore the impact of intermittent fasting on participants' quality of life and fatigue using validated questionnaires. The third objective is to compare the effect of the two prevailing fasting windows including early morning feeding window (8 a.m.-4 p.m.) and late feeding window (12 p.m.-8 p.m.) on sleep and quality of life.

The investigators expect that intermittent fasting would have a positive effect on sleep and would allow participants to experience an improvement in their sleep during this practice. The investigators also assume that intermittent fasting would have a positive effect on participants' quality of life and fatigue. Moreover, intermittent fasting during the early morning feeding window (8 a.m.-4 p.m.) would have a more positive impact on sleep and quality of life compared to the late feeding window (12 p.m.-8 p.m.) because it would be more aligned with the circadian rhythm.

This project will be conducted over a 10-week period. Subjects will be divided into two groups (group A and group B) that will alternate their fasting windows each month. Each group will consist of 36 male and female volunteers, adults, aged between 18 and 65 years old, and with a BMI between 18.5 and 29.9.

At recruitment, all subjects will provide their written informed consent prior to enrolling in the study. Once the subject's consent is obtained, the participants will be randomly assigned to Group A or Group B. More specifically, during baseline assessment, the participants will randomly draw an envelope containing a piece of paper labeled Group A or Group B. There will be as many envelopes as there are participants, half containing the Group A paper and the other half containing the Group B paper. Once the subject will be assigned to their group, they will be labeled with a number (ranging from 1 to 36) which will allow us to maintain their anonymity.

The study will last 10 weeks in total, with 4 weeks for each window, followed by a 2-week "washout" period where the subjects follow their usual diet between each group of 4 weeks intermittent fasting period. For the first month, group A will follow a feeding period from 12 p.m. to 8 p.m. (known as late feeding window) and group B will follow a feeding period from 8 a.m. to 4 p.m. (known as early feeding window). The following 2 weeks both groups will return to their usual eating habits. For the second month, group A will follow an early feeding window while group B will follow a late feeding window.

At enrollment, information concerning baseline characteristics such as age, body mass index (BMI), profession, physical activity, usual eating habits and smoking status, will be collected.

During baseline assessment, at the end of each month and at the end of the washout period all participants will complete four validated questionnaires to assess any changes they may have experienced in sleep, quality of life, fatigue, and physical activity. Moreover, during these appointments, anthropometric measurements including height (cm), BMI (kg/m2), muscle mass (kg), visceral mass (kg), fat mass (kg), bone mineral mass (kg), waistline (cm) and waist-hip ratio will be carried out using impedance scales in order to observe any possible changes on body composition. Lastly, participants will be asked verbally to mention if they have experienced any side effects such as headache, vertigo, nausea, vomiting, abdominal pain, changes in bowel movements, fatigue, mood swing.

Subjects will also be required to use the Automated Self-Administered 24h Dietary Assessment (ASA24) Tool software once per week, which is a 24-hour food diary. Its purpose is to collect detailed and accurate information on all foods, beverages, and supplements (vitamins, minerals, etc.) consumed by the subject during the last 24 hours. Data concerning total energy intake (kcal/day), protein intake (gr/day), carbohydrates intake (gr/day), fat intake (gr/day), fibers intake (gr/day), amount of water (L/day) and alcohol intake (gr/day) will be analyzed.

The primary outcome of this study will be to investigate the impact of intermittent fasting on sleep including sleep quality, efficiency, duration, and sleep latency among healthy individuals. This will be carried out using the PSQI - Pittsburgh Sleep Quality Index: a standardized self-report questionnaire assessing the subjective sleep quality, sleep efficiency (percentage of time spent in bed actually asleep), sleep duration, and sleep latency (time taken to fall asleep) over the last month. It consists of 19 items, resulting in a total score of 0 to 21. Scores above 5 can be used as an indicator of poor sleep quality.

The second objective will be to explore the impact of intermittent fasting on participants' quality of life using the validated questionnaire Short Form Health 36 (SF-36) that objectively measures quality of life by covering eight domains of health. Sf-36 assesses eight scales: physical functioning, role limitations due to physical health, bodily pain, general health perceptions, energy/fatigue, social functioning, general mental health (emotional well-being), and role limitations due to emotional health, measured by 36 questions, with an additional question on health change/transition. All scores will be recoded with a maximum score of 100. A higher score indicates a better quality of life.

Another primary outcome that will be explored is the impact of intermittent fasting on symptoms of fatigue. This will be carried out using the Fatigue Assessment Scale (FAS), a 10-item scale assessing symptoms of chronic fatigue.

In addition, the impact of intermittent fasting on physical activity will be examined using the Global Physical Activity Questionnaire (GPAQ). Information concerning participation in physical activity in three areas (work activity, travel to and from places, recreational activities) as well as sedentary behavior will be collecting through 16 questions.

Inclusion Criteria:

• Healthy subjects
• Adult subjects - age: between 18 and 65 years old
• Subjects with a BMI between 18.5 and 29.9 kg/m^2
• Male and female subjects

Exclusion Criteria:

• Subjects < 18 years old
• Subjects with Diabetes Mellitus (type 1 and type 2)
• Pregnant and/or breastfeeding and/or postpartum women
• Underweight subjects (BMI < 18.5)
• Obese subjects (BMI > 30)
• Subjects with confirmed sleep disorders (requiring CPAP or sleep medication (sleeping pills))
• Subjects with renal failure (GFR < 30 ml/min/1.73 m^2) or liver disorder
• Subjects with serious cardiovascular, respiratory, neurological, or metabolic medical conditions
• Subjects with malignant tumors
• Subjects with a serious mental disorder requiring medication (e.g., antidepressants or anxiolytics)
• Subjects with eating disorders
• Subjects who have undergone major surgery or have been hospitalized due to major medical condition (surgery, stay in intensive care) within the last one year
• Subjects who have lost more than 10% of their body weight within the last one year
• Subjects actively participating in a weight-loss program
• Subjects with alcohol use disorder (maximum 10 standard alcoholic drinks per week, 2 standard alcoholic drinks per day)
• Subjects with substance use disorder
• Subjects unable to provide informed consent
• Subjects who do not participate simultaneously in another clinical trial

all the individual participant data that uderlie the results reported in this study after deidentification.

Immediately following publication. No end date.

researchers who provide a methodologically sound proposal