Sleep is arguably the most important element of any healthy lifestyle. Sleep, light, diet, exercise, and play, will inevitably influence one other in a variety of different ways. For example, exercise too little and your body not only recognizes the futility of retaining muscle mass, but as energy expenditure decreases, sleep disturbances will often manifest as you have less to heal from.
On the other hand, practice poor sleep hygiene and your ability to recover from exercise sinks to zero - or close to it. Further still, little to no exposure to natural light combined with late night blue light screen time, causes a circadian phase delay thus disrupting hormone homeostasis in conjunction with your ability to both sleep and recover.
Sleep is the great equalizer, but I like to call it the great actualizer, meaning it is the thing that manifests proper healing and hormonal/metabolic function.
It should be in the back of your mind that everything you do throughout the day be in the causal chain to improving sleep. On most days, you're seeking to exhaust yourself in as many dimensions as possible so that when darkness hits, you start feeling the pulses of melatonin, and the natural pull towards bed.
Jordan Peterson - the Canadian professor of clinical psychology - mentioned in one of his interviews that one of the most important determinants of health is the circadian rhythm. Specifically, he spoke to the importance of waking up at the same time every day, and that this is crucial for developing a productive routine.
While I agree that the routine is of utmost importance for the person seeking to be more productive, I disagree that it starts in the morning.
The daily routine actually starts the night before.
Circadian phase delay results in disrupted hormone cascades, the result of which can lead to deteriorating health markers and an inability to wake-up naturally with the sun. Anyone who's ever spent a night staring at their computer until 3 am, or eaten dinner after 11 pm is probably aware of this. When you finally wake up, it feels like you've been hit by a truck.
About three hours after your last meal - through a series of enzymatic reactions - the amino acid tryptophan is catalyzed to serotonin. The neurotransmitter serotonin is then methylated in the pineal gland to form melatonin - the body's sleep hormone.
And, after this process is underway, the amount and timing of melatonin release will in turn influence the amount of human growth hormone released by the anterior pituitary gland. Growth hormone will then function to mobilize fat stores, build lean muscle, and support normal immune function throughout the night.
This is why circadian phase delay is so problematic. It takes about 3 hours after your last meal for melatonin secretion to peak, so if that final meal is pushed back to say, 11 pm, then you're looking at 2 am before you feel tired enough to actually fall asleep. Then, growth hormone peaks for somewhere between 1.5 - 3.5 hours after the onset of deep sleep, but peak secretion is delayed if the onset of sleep is delayed.
This obviously has implications if you're only getting 4-6 hours of sleep per night.
It typically takes 90 minutes after the onset of sleep to attain a deep sleep phase, so the less you sleep, the more your eating into the pulses of growth hormone that are supposed to come along with a regular 9 hour sleep cycle - which of course means less healing, less fat burning, less muscle building, and worsened immune function.
So ultimately, my suggestion is that you cease food consumption 2.5 - 3 hrs before you'd like to fall asleep. If your final meal of the day occurs somewhere between 6 pm and 7 pm and you turn off the bright lights just after sundown, this would strike me as reasonable, and it will help ensure you're not only practicing proper sleep hygiene, but you'll also be able to enjoy all of the downstream effects as, including optimizing tomorrow's all important daily routine.