|In general it's certainly a good idea to rise, when the cock crows on the dung heap, but what if that means you miss 90 min of your precious sleep?|
Can you "wake your way" towards obesity?
"Mild sleep restriction" is what scientists call it, when you miss 'only' one hour of your regular 7-8h of sleep every night and "mild sleep restriction" is also what the 19 healthy young normalweight men in the Robertson study have been exposed to over a three-week period.
Before the actual study began, the habitual sleep patterns were assessed by actigraphy and sleep diary information collected during a two week baseline period. The subjects were then randomized to either the
Healthy male students, aged 20–30years, BMI 19–26kg/m² were recruited for this randomized–controlled sleep intervention study [...] those with a self-reported sleep length of 7.0–7.5h were invited for more detailed screening.[...] According to self-report, volunteers were not taking prescription or over the counter medication and had a stable weight for >3months. Specific exclusion criteria also included (i) shift-work and travel beyond 2 time zones in the preceding 2months, (ii) high intake of caffeine and alcohol, (iii) extreme morning or evening preference assessed with the Munich Chronotype and Horne Östberg Questionnaire, (iv) a self-reported sleep problem (Pittsburgh Sleep Quality Index global score≥6) and (v) daytime naps in the preceding 4weeks.
Just in case you have forgotten about it, you can do the Munich Chronotype test for free (including personal evaluation) right at the website of the University of Munich (click here to be redirected)
- restricted group spending their regular time-in-bed minus 1.5h per night, or the
- habitual group who simply followed their habitual sleeping patterns
|Figure 1: Relative changes of insulin sensitivity (HOMA-IR), fasting blood glucose and adiponectin levels in the course of the three-week study period (Robertson. 2013)|
|Figure 2: Illustrated and annotated version of the graph depicting the change in insulin sensitivity in the habitual (open circles) and sleep restricted (closed circles) group (Robertson. 2013)|
"[...] some of the effects of sleep restriction appear transient, i.e. we have beenunable to confirm a change in insulin sensitivity beyond one week of sleep restriction [and that t]he data clearly indicate that the effects of a reduction in sleep duration may change in the course of the exposure to sleep reduction, [which renders any] extrapolation from single visit laboratory studies to epidemiological data problematic." (Roberston. 2013)If we would yet discard the epidemiological findings and simply ignore the constant increase in fasting blood glucose and rely on the fact that the insulin tolerance returned to baseline after an initial drop, we could even (ab-)use the data from the study at hand to argue in favor of sleep "deprivation" (I am deliberately using quotation marks, because the previously mentioned adapation process would suggest that the subjects were not actually "deprived") as a means to reduce the obesity epidemic. After all the subjects in the sleep restricted group did lose some body weight and reduced their adiposity index, the waist equivalent to the BMI (higher values = higher ratio of waist to body height), by meager, but at least measurable 0.8%.
|Believe me: Fridge raiding is your least problem if you don't sleep at night. If you want to know more about the profound metabolic, psychological and even carcinogenic effects of having or not having a regular sleeping rhythm, why a dark room is important and more, read up on the Circadian Rhythm Series|
So what? You cannot 'wake yourself lean', can you?
No, probably not. The evidence from epidemiological studies is too overwhelming to throw the insufficient sleep = diabesity hypothesis over board. On the other hand, the results of the study at hand are interesting, as they clearly suggest that (a) our bodies are able to adapt to a news steady state within a certain window of suboptimal to optimal sleeping time and (b) that the short term effects of what I would like to identify as an actue stressor, namely 1-2 weeks of reduced sleep will lead to similarly transient weight loss.
|Previous study showed: When you are dieting 40min extra sleep can help you 1lbs extra fat (read more).|
Bottom line: Now, does this mean that we have been overrating the importance of sleep hygiene before? Certainly not. What we may have underestimated, however, are short-term compensatory effects which allow for a brief, but non-negligible time window, in which neither the acute very short-term effects - nor the chronic (very) long-term effects of sleep deprivation will harm you. And though we don't know anything about the size of this window, one thing appears to be certain: It's large enough for exam preparations, but not for years of drinking, partying and doing all sorts of things but sleeping ;-)
- Robertson MD, Russell-Jones D, Umpleby AM, Dijk DJ. Effects of three weeks of mild sleep restriction implemented in the home environment on multiple metabolic and endocrine markers in healthy young men. Metabolism. 2012 Sep 15.