Circadian phase advance: going to bed earlier, waking up earlier. Blue blockers at sunset, bright light at sunrise. Flying east. Autumn.
Circadian phase delay: staying up late, sleeping in. Flying west. Spring. Using smart phones, tablets, and iPads in bed at night. Light pollution.
Relative to adolescents, infants and children are circadian phase advanced. This is part of what is fueling the movement to delay high school start times. Kids are mentally better prepared to work later in the day. With early school start times, performance is down in the morning, but they kill it on video games after school. Delaying start time by an hour won’t totally fix this, but could help.
Edit: it seems like a similar movement is happening for adults, too – ie, starting work an hour later.
I’m not saying everything healthwise deteriorates with age, but the gradual circadian phase delay that occurs with aging and overusing blue light-emitting devices at night might not be a good thing. If a particular diet can promote phase advance, why not? (at least it’d be countering the phase delay).
Possible role of diet
In the top half of the figure below, it’s mice fed a “normal diet (ND) (high carbohydrate)” (Oishi et al., 2012). During normal “light dark (LD)” conditions, movement and feeding is concentrated in the active phase. When the lights are permanently turned off in “dark dark (DD)” conditions, the free-running circadian clock begins to shift slightly forward (phase advance), but nothing drastic.
In the bottom half of the figure, during normal LD conditions the mice are switched to a low carb, high protein diet. Note how activity shifts leftward (phase advance) during the LD condition. When low carb, high protein-fed mice are then switched to DD, we can see a clear circadian phase advance.
Low carb, high protein-fed mice ate more but didn’t get fat; physical activity and body temperature were unchanged. But this post isn’t about that. Gene expression of key circadian transcription factors in liver and kidney exhibited phase advances.
The next figure is study to the one above, although instead of switching to a low carb, high protein diet, the mice were switched to a low carb, high fat diet (Oishi et al., 2009).
Note the similarity of control (high carb diet) mice: gradual phase advance when switched to DD:
The phase advance is markedly enhanced in low carb, high fat-fed mice.
The circadian regulation of activity is similarly affected by low carb, high protein, and low carb, high fat diets. What do those two diets have in common?
A bit of a stretch? carbohydrate restriction mimics some aspects of avoiding artificial light at night and being young: phase advance. Whether the carbs are replaced with protein or fat doesn’t seem to matter in this aspect.
Wanna know what else can do this? FOOD. The food-entrainable oscillator (FEO) kickstarts circadian rhythms. Rodent studies have shown that timed feeding, regardless of the actual time, consistently realigns the circadian expression of numerous genes (eg, Polidarova et al., 2011 and Sherman et al., 2012).
So what’s the hack? Food: do more of it, earlier in the day. Phase advance. Kind of like avoiding artificial light at night or being young.
Oh, and mice exposed to dim light at night (who are pretty much metabolically screwed)? phase DELAYED (Fonken et al., 2010).