Social jet lag

Social jet lag is basically a general term that refers to circadian arrhythmia.  Sort of like insulin resistance, it’s rampantly abundant — some have estimated a prevalence of up to 75%!  Social jet lag can be induced by shift work, East/West travel, late meal timing, artificial light at night, sleeping late, not enough sunlight in the morning, etc., etc.  And while any of the above insults, by themselves, may not really screw up your circadian rhythms, you can see how easy it is for one person to fall prey to nearly of them:

Eat a late dinner, stay up late using artificial light (eg, computer, smart phone, etc.), sleep late the following day so you skip breakfast and don’t get any sunlight in the morning.


This increases your risk for a wide variety of ailments, ranging from cancer to diabetes to bipolar disorder: no bueno.

One key mediator of the effects of LIGHT is melatonin.  Artificial light at night suppresses melatonin.  Sunlight in the morning can blunt the impact of this!  It all ties in together.  Gravitas.

Great review article here.



Jane Plain noted that cortisol is anti-proliferation and the AM cortisol spike (also known as the Cortisol Awakening Response) blunts cell division…

Melatonin sensitizes the system!

  1. Proliferation occurs at night for many cell types
  2. melatonin is ‘sensitizing’ these cells to process a big nutrient influx
  3. cortisol shuts down proliferation in the morning
  4. time to eat and get some sunlight!


Entraining central and peripheral clocks




Early to bed, early to rise, yada yada yada.  LIGHT & food in the morning.  No artificial light at night.

Can’t do these?

Light boxes in the morning can help.  Blue blockers at night.  Shift meals toward earlier in the day.

In general, most of these interventions function to “advance” the circadian phase, and Jane Plain wrote a great blog about how lithium also does this by inhibiting GSK-3b, which preserves REV-ERB alpha.

For what it’s worth, keep an eye on REV-ERB alpha; I think it’s one of the more important life-and-death circadian mediators.



lithium and GSK-3b


Circadian rhythms are more important than the carb vs. fat debate, imo.  Some people say we need to eat a certain way because we’ve been doing so for thousands of years.  Yeah, well, we’ve had circadian rhythms for BILLIONS of years!


disclaimer: I honestly don’t really like making the Evolutionary™ argument to support circadian rhythms simply because we have so many modern studies on it.  And who knows, our modern #context is so different from as little as 50 years ago… the Evolutionary™ argument is important, but I tend to put more weight on proper intervention studies.






Some of the modern studies (and/or blog posts about them):

Importance of bright light in the morning

Bright light in the morning attenuates the light-induced melatonin suppression at night (eg, Kozaki et al., 2015)

Blocking artificial light at night with hot Blue Blockers

Eat breakfast like a King, lunch like a prince, and dinner like a pauper: Afternoon Diabetes and Dawn PheNOMNOMNOM

Now, compare the studies on LIGHT, melatonin suppression, and meal timing with those on low carb vs. low fat:  circadian rhythms can be really messed up in the former studies, and no big difference in the latter… assuming #context is taken into account and we’re talking about real whole foods, duh.

That’s all, for now.


calories proper


Become a Patron!



Be Sociable, Share!
  • John Woodslave

    I eat before bed a quark (for the casein) and whey combo (for the hope of some muscle building or az least retention). Does it mismatch my c clock? I feel fuller in the morning.

    I wont lie I am (was) big fan of IF and eating later but your blog makes me thinking (kinda hate you for this lol) so I try things out (eating breakfast lol). But still not clear about insulin sensitivity and carb in the morning… I hate so much this many conflicting theory…

    • eating at night is one of many factors which function to “delay” your circadian phase. If all your other ducks are in a row and you’re generally healthy, this won’t kill you

  • rs711

    I like this post Bill.

    “Evolutionary™ argument is important, but I tend to put more weight on proper intervention studies.” ==> That’s fair. Evolution is, by definition, what moulded our present-day responses to our modern environment. So it’ll always matter. Any controlled/modern intervention study can only “make sense” or “be true” if it fits within our evolutionary path (with what actually happened, not what we think happened). But we often just don’t how how evolution shaped up. So in those instances, putting more weight on intervention studies is smart.

    “Circadian rhythms are more important than the carb vs. fat debate, imo” ==> more, less, who knows. what we do know is that food & circadian rhythms both drastically affects IR/IS. their undeniably both important. ranking their importance is a secondary concern (to me at least) as we should be paying attention to both. you may be right. i dont know.