Help deciphering sleep study: Influence of Sleep Restriction on Weight Loss...

Hi all,

Been trying to figure this one out for a while, feels like my smooth brain is missing something obvious. Interested in the effects of somewhat chronic mild sleep deprivation where you get enough to get by but not an optimal amount for training. This one wasn’t covered in the Sleep article as far as I’m aware, and compares caloric restriction to caloric restriction plus 90 mins of sleep restriction 5 days a week with sleep ad lib’d on weekends.

“The CR and CR+SR groups lost similar amounts of weight, lean mass, and fat mass. However, the proportion of total mass lost as fat was significantly greater (p=0.016) in the CR group”

Table 2 shows that change in bodyweight, weight loss relative to baseline, fat mass (kg), lean mass (kg), and bodyfat % were all nonsignificantly different between groups, but that “Total mass lost as fat mass” was significantly different, as well as total mass lost as lean mass.

I don’t really see how this is mathematically possible if all measurable outcomes were nonsignificantly different, without being some sort of clinically irrelevant outcome as a result of analysis. It’s been a while since I did detailed stat analysis, but some curious things are that the CI’s on “Total mass loss as fat mass, %” are massive, at least for the CR+SR group (16.9 +/- 104.5). The IQ range is more reasonable, but still large (median of 58.4 [-12.7, 73.6]).

So does this mean some people were drastically affected, and others less so? Does it imply a clinically irrelevant difference, or bad statistical analysis? Or am I missing something obvious?

Thanks a bunch!

RVR,

While I haven’t reviewed this specific study, we published an article, podcast, and research review on this finding from other studies. They are available here:

Article: The Effects of Sleep Restriction on Weight Management and Body Composition | Barbell Medicine
Podcasts:
Stream Episode #169: February 2022 Research Review by Barbell Medicine | Listen online for free on SoundCloud
Stream Episode # 97: May 2020 Research Review by Barbell Medicine | Listen online for free on SoundCloud
Review:Issue 17 - May 2020 - Barbell Medicine

As far as the math in the particular study you linked, I would recommend contacting the the authors for clarification. We think that reduced sleep likely portends a worse outcome on LBM preservation during an energy deficit, while also having not-great effects on appetite, satiety, and pretty much every organ system.

I don’t think further discussion on this particular paper is something I’m interested in, but if you have specific questions otherwise, we’d be happy to answer them.