Meal timing &
sleep in different
Chronotypes
Does the timing of meals affect the health
and sleep of night owls and early birds
differently?
Researchers at the University of
Sydney and MRC seek the answer : Does the
timing of meals affect the health and
sleep of night owls and early birds?
Why Is Meal Timing Important?
Meal timing plays a crucial role in regulating sleep by influencing the body’s internal clock, or circadian rhythm. Eating too late at night can disrupt sleep by delaying melatonin production and increasing body temperature, making it harder to fall and stay asleep. On the other hand, eating too early in the evening may help align digestion with the body’s natural sleep-wake cycle, promoting better sleep quality. Studies suggest that irregular meal timing, especially late-night eating, is linked to shorter sleep duration, poorer sleep efficiency, and an increased risk of sleep disorders. By maintaining a consistent eating schedule, especially avoiding heavy meals close to bedtime, individuals can support both their sleep patterns and overall health.
Why Does Chronotype Matter in Terms of Meal Timing
and Sleep?
Chronotype, or an individual’s natural sleep-wake preference (such as being a night owl or an early bird),plays a key role in how meal timing affects sleep. Night owls tend to eat later in the evening, which can
misalign their digestion with their circadian rhythm, leading to poor sleep quality and metabolic issues. In
contrast, early birds usually eat earlier, aligning their meals with their body’s natural biological clock, which
may promote better sleep and metabolic health. Research suggests that mismatched meal timing—such as
eating late at night for early chronotypes or skipping breakfast for night owls—can negatively impact sleep
duration, hormone regulation, and overall well-being. Understanding one’s chronotype can help in optimising
meal timing to support better sleep and overall health.
How to participate
Click the join the study link below, complete the short survey and a member or our team will get in touch with the next steps.
We are seeking:
Healthy adults between 18 and 45, with no chronic or acute disorders
What does this study involve?
In this study, participants will be randomly assigned to one of two groups: either having their last meal four
hours before bedtime or one hour before bedtime. After a 10-day washout period, they will be assigned to the
other group.
Participants will be required to provide stool, saliva, and blood samples, complete daily online surveys on diet, meal timing, and sleep for one month, attend three in-person meetings, and provide blood pressure and anthropometric measurements.
Participants in this study will receive a gift card as compensation for their participation.
You may be eligible to participate in this study if you:
Can provide a stool, blood, and oral swab samples
Can have some clinical measures taken e.g. height, weight and blood pressure
Can complete a survey about your diet, sleep, physical activity, and chronotype
Can wear an actigraphy watch throughout the month of the study period.
Have not had traveled across time zones in the past month
Are not a Shift worker
Have not been diagnosed sleep disorders such as insomnia, sleep apnea, etc.
Are not taking medication affecting sleep including melatonin, Zolpidem, Lorazepam, Antidepressants, etc.
Are not pregnant or lactating (for women)
Have not been Yoyo dieting or changing your usual diet during the past month
Have not observed blood in their stool during the past month
Have not had antibiotics in the past 3 months.
Frequently asked questions
How long does the study last?
This study lasts for about a month. You will provide your first set of samples at
the beginning of the study, then wear a watch and complete a survey every day
for two weeks. Next, you will participate in a three-day intervention before
attending a second meeting to provide another set of samples. After that, you will
continue wearing the watch and completing the survey for 10 more days. Finally,
you will undergo another three-day intervention and provide your last set of
samples at the final meeting.
What is the intervention?
The intervention focuses on the timing of your final meal of the day. You will be
randomly assigned to one of two groups: either having your last meal four hours
before bedtime or one hour before bedtime. After a 10-day washout, you will be
assigned to the other group
What samples would I need to provide?
You will be providing blood, stool and saliva samples at 3 different time points.
How long are the in-person meetings?
In-person meetings take about 40 minutes.
How long do the surveys take to complete?
The initial comprehensive survey takes approximately 20 minutes to complete while the daily surveys, which include dietary and sleep questionnaires, take around 5–10 minutes each.
Approvals
This study has been Approved by the University of Sydney Research Ethics Committee approval number: 2024HE000052
This study is registered on the ANZCTR, ACTRN12620000106932
This study is conducted by the University of Sydney in collaboration with the MRC
Text version Version 1, 5th March, 2025
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