Does the time you eat affect how well you sleep?
When you eat influences your biological clock and probably also how well you sleep. The strongest practical takeaway is: try not to schedule your main meals too late in the evening, as that fits better with your body's natural rhythm.
The time at which you eat influences your biological clock. Your liver, muscles and fat tissue have internal clocks that align your metabolism with when they expect food. If you regularly eat at times that clash with your day-night rhythm, that alignment is disrupted. This has consequences for your metabolism and health, although how large that effect is has not yet been established for every aspect.
What you eat and when you eat also influences the bacteria in your gut. Those gut bacteria produce substances that help regulate sleep, including melatonin (the sleep hormone), serotonin and GABA (a calming substance in the brain). A plant-based dietary pattern appears to promote the production of these substances. The direct evidence in humans is still limited here, so firm conclusions cannot yet be drawn from it.
Night owls, people with a strong preference for staying up late, more often eat their main meals late in the day. They adhere less well to a healthy diet and have, on average, a higher body mass index and more of the hunger hormone ghrelin in their blood. Whether their late eating pattern worsens their sleep, or conversely whether their sleep rhythm drives their eating behaviour, has not yet been fully investigated.
Eating late in the evening, and thereby breaking the usual overnight fast, has been studied in the context of metabolism and sleep. Researchers indicate that more targeted research is needed to understand when this is harmful and when it is not. One practical exception is travelling across time zones: aligning meals with the schedule of your destination appears to reduce jet lag in athletes, although this evidence is preliminary.
Claims are based on reviews (narrative and systematic) and one experimental study in exercising adults. No large RCTs specifically targeting meal timing and sleep quality. One claim about light exposure has been included as contextual background, but not as direct evidence.