Is When You Eat as Important as What You Eat?

Recently, a number of studies have looked at the impact of sleep deprivation, disruption of the sleep-wake cycle, and shifts in circadian rhythm on feeding behaviour and propensity to gain weight (facit: they are all bad!).

This is probably because, a complex biological clock machinery translates time information into physiologically meaningful signals by the regulation of hundreds of clock-controlled output genes (CCGs) that control virtually all aspects of cellular function.

From an evolutionary perspective this makes a lot of sense as certainly bodily functions make sense in the wake state but are not required whilst asleep, while other functions are best managed during night time, when the organism should normally be asleep.

Now there is work emerging that some of these metabolic changes can be reset or readjusted by the timing of food intake.

One such study is the one by Barclay and colleagues form the Max Planck Institute of Biophysical Chemistry, Göttingen, Germany, just published in PLoS One.

Based on the emerging body of evidence that shiftwork is associated with adverse metabolic pathophysiology potentially involving direct physiological effects of nocturnal light exposure, or indirect consequences of perturbed endogenous circadian clocks, the researchers used a two-week paradigm in mice to model the early molecular and physiological effects of shiftwork.

During this time, animals were kept awake during their regular sleeping hours and were provided foods either during their normal waking hours or their ‘night shifts’.

According to their findings although the two weeks of timed sleep restriction had rather modest effects on diurnal activity patterns, feeding behavior, and clock gene regulation in the circadian pacemaker of the suprachiasmatic nucleus, microarray analyses revealed considerable global disruption of diurnal liver transcriptome rhythms, enriched for pathways involved in glucose and lipid metabolism.

Much of these metabolic abnormalities were prevented by restricting food intake during the ‘night shift’ and providing access to foods only during the beginning of ‘normal’ waking hours.

Thus, the authors conclude that,

“Although altered food timing itself is not sufficient to provoke these effects, stabilizing peripheral clocks by timed food access can restore molecular rhythms and metabolic function under sleep restriction conditions.”

They thus further speculate that,

“…strengthening the peripheral circadian system by minimizing food intake during night shifts may counteract the adverse physiological consequences frequently observed in human shift workers”.

Obviously, these findings need to be replicated in human shift worker. I, for one, can certainly attest to the fact that the notion of not eating during long night shifts may well prove a challenge for most people (particularly during the wee hours of the morning when cravings for sweets and junk food seem the hardest to resist). On the other hand, I do recall that the nights, where I had a normal dinner prior to starting a shift were less problematic than taking a midnight or early morning break for a meal.

I would certainly love to hear from readers about their experiences with eating and weight gain during shift work and how they deal with shifting sleep wake cycles.

Red Deer, Alberta

ResearchBlogging.orgBarclay JL, Husse J, Bode B, Naujokat N, Meyer-Kovac J, Schmid SM, Lehnert H, & Oster H (2012). Circadian desynchrony promotes metabolic disruption in a mouse model of shiftwork. PloS one, 7 (5) PMID: 22629359