This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1 · go to the accepted answer.
Building on post #88 rather than restating it.
Sleep quality versus quantity: some people report changes to sleep duration; others report changes to sleep quality without duration change. Both can matter for recovery and daytime function.
Happy to be corrected if someone holds better data than mine.
Apnoea monitoring: if you have diagnosed or suspected sleep apnoea, periodic monitoring (annually) during weight loss is prudent because severity changes.
Post #94 and I disagree about the size of the effect, not about the direction.
Stimulants and sleep: if supplementing with caffeine or other stimulants for energy during weight loss, timing and dose matter for sleep. Evening stimulant use interferes with sleep.
Adding it in case it saves somebody the afternoon it cost me.
Adding a data point of agreement rather than a data point.
Gastrointestinal effects overnight: nausea or reflux or constipation at night can disrupt sleep. Dosing timing (morning versus evening) might help if nighttime GI symptoms are the problem.
Sleep looks different depending on whether you are reading the primary literature or the summaries of it, and the difference is not in our favour.
Appetite suppression and nighttime eating: if nighttime eating was a pattern, appetite suppression changes that pattern. Sleep can worsen if nighttime waking is habitual and now there is no appetite-based reason to wake.
It is the sort of thing that seems obvious in retrospect and was not at the time.
Sleep hygiene: basics (cool dark room, consistent sleep time, no screens before bed) matter more during energy deficit because stress and sleep need are higher.
That has been true for the cases I have seen and I have not seen many.
Where I part company with post #100, and it is a narrow parting.
Fatigue during the day and poor sleep at night are different problems with different causes and get merged in most accounts here.
The evidence for this is thinner than the way I have phrased it suggests.
Narrowing post #102, because the general version has more than one answer.
Eating patterns shift substantially and late intake affects sleep independently of anything pharmacological.
A modest claim, modestly supported.
Consistency of timing does more for most people's sleep than any intervention discussed in this subcategory.
If that reads as pedantic, it is, and it has saved me twice.
Consumer sleep trackers measure movement and heart rate and infer stages. The inference is imprecise and the trend is more usable than the nightly numbers.
Post #104 put the caveat in the right place and I want to underline it.
The published data on sleep outcomes in this class is thinner than the volume of discussion, which is worth saying plainly.
This is the sort of exchange that makes the archive worth searching.
I had written a reply contradicting post #111 and deleted it. Here is what survived.
A sleep diary with times rather than impressions is the only way to tell a real change from a remembered one, and it takes a minute a day.
I have said this before in a thread nobody could find, so it is worth repeating.
Nothing here is medical advice, and suspected sleep-disordered breathing specifically is something to have assessed properly rather than tracked.
Appetite suppression and nighttime eating: if nighttime eating was a pattern, appetite suppression changes that pattern. Sleep can worsen if nighttime waking is habitual and now there is no appetite-based reason to wake.
Where I part company with post #114, and it is a narrow parting.
The documentation on sleep is better than this thread and I say that as someone who has posted in the thread.
Post #117 is the version of this I will quote in future. One addition.
Apnoea monitoring: if you have diagnosed or suspected sleep apnoea, periodic monitoring (annually) during weight loss is prudent because severity changes.
That holds under the stated conditions and I have stated them.
Post #117 and I disagree about the size of the effect, not about the direction.
Obstructive sleep apnoea: pre-existing OSA can worsen with weight before it improves (apnoea-hypopnoea index goes up as soft tissue inflames before weight is lost). This is self-limited but uncomfortable during active weight loss.
That has held every time I have looked, which is not the same as always.
Taking post #119 at face value and following it one step further.
The honest answer on sleep is that it depends, and the useful part is the list of what it depends on. Four items, in rough order of how much they matter.
Most people get the first two right and then argue about the fourth.