The Impact of Sleep Restriction on Gastric Emptying, Appetite and Energy Intake

This study aims to examine if partial sleep deprivation results in alterations blood markers and subjective markers of homeostatic, and hedonic appetite, as well as provide initial data as to the impact of sleep restriction on gastric emptying.

The proposed study will take the form of a within-subjects, randomised crossover experimental design. The data will be quantitative. The study will take place for total of approximately 5 weeks / 37 days (+ up to 6 weeks depending on their schedule: Minimum duration = 5 weeks (37 days), Maximum duration = Approximately 11 weeks (79 days).

Following a telephone screening, participants will be provided with a pre-paid envelope containing secondary screening questionnaires in the form of paper documents. Either by drop-off or post to at their place of residence or place of work. The secondary screening documents are detailed under Inclusion / Exclusion criteria and Secondary screening sub-headings. Participants will then return the filled-out inclusion / exclusion documentation if they still desire to take part in the study, either through the pre-paid envelope, or to be picked up by the research team. A member of the research team will then analyse the participants responses and inform them of their eligibility to take part, via email. Following this, participants will be invited to the lab.

Upon entering the lab, participants will be provided with an informed consent form to sign. Following this, demographic information will be collected (Approximately 45 minutes to an hour): This is detailed under the preliminary data collection sub-heading. During this visit, the participant will also be provided with an actigraphy device in order to measure habitual sleep times for one week. Following this, participants will continue to be wear the actigraphy device for a subsequent week, with participants maintaining habitual duration of time in bed, although with (Potentially) altered bedtime, with 7am wake times, in order to standardise participants to 7am wake times and eliminate any erratic sleeping behaviours leading up to the first experimental trial. Participants will also be provided with a food intake and activity diary. The following visits will take the form of experimental trials (Habitual vs 50% habitual sleep): In which the variables of interest will be tested. Namely, blood markers of appetite, self-reported appetite scores, food preference and craving, heart rate variability, gastric emptying, and energy intake. Participants will not be compensated for taking part in the study but will be reimbursed the cost of travelling to and from the lab.

Eligibility Criteria:
Inclusion

1. Healthy (As assessed with medical screening questionnaire)
2. Self-reported habitual bedtimes between 7 to 9 hours (As assessed with the Pittsburgh sleep quality index)
3. Between the ages of 18 to 45

Exclusion

1. Participants will also be excluded from participation if they are pregnant.
2. Current smokers
3. Excessive alcohol (\>2 drinks per day)
4. Excessive caffeine (\>300mg per day)
5. Musculoskeletal injury.
6. Shift work during the past 4 weeks
7. Travel across more than one time zones during the past 4 weeks.
8. An indication of having a depressed mood (As assessed by a score on the Centre for Epidemiologic Studies of Depression scale above 16).
9. Moderately or highly physically active, as determined by the International Physical Activity Questionnaire (IPAQ) short form.
10. Excessive daytime sleepiness as measured by the Epworth Sleepiness Scale (Score \> 10) (ESS) (Hart et al., 2015).
11. Participants will also be considered ineligible if they achieve a score indicative of narcolepsy or chronic insomnia, as assessed through the Pittsburgh Sleep Quality Index \[PSQI\] (Score \> 5) (Hart et al., 2015).
12. Participants must achieve a score \< 50 on the Food Craving Questionnaire-Trait-reduced (FCQ-T-r), which has been shown to discriminated between individuals with and without "food addiction" with high sensitivity (85%) and specificity (93%) (Meule et al., 2014).