In recent years, the role of our internal clocks in governing body functions and even behavior along the 24-hour day cycle has gained increasing attention. Epidemiological as well as experimental lab studies have established a clear link between circadian (i.e. 24-hour) rhythm disruption and an increased risk for a whole row of very common and highly detrimental diseases – from depression to obesity and even cancer.
While these connections are widely known, it is surprising how little of this knowledge has yet transmitted into medical practice and advice in professional settings. It is still widely conceived that those who care little about their endogenous clocks and physiological demands are the toughest, smartest and, ultimately, most successful acteurs d’affaires of the professional world.
Little by little, this notion is changing. Interval fasting is becoming one of the new dogmas of weight management and constant daily routines have to some extent lost their traditionally dull image. Recent work in animals and humans suggest that the influence of the circadian clock system on performance and well-being go even further, deciding how our bodies respond to the cannonade of stressful events that we all inevitably encounter during business and private life.
As we and others have shown over the last years, circadian clocks are found all over the different tissues involved in the body’s stress regulation – from the brain down to the adrenaline and cortisol-producing adrenal glands and the adipose tissue that mediate much of the metabolic effects of chronic stress exposure. In all these tissues, clock genes are rhythmically active along the day, thus modulating tissue responses to stress-associated stimuli. Experiments in mice suggest that a functional clock system is essential for normal stress responses, affecting both acute as well as long-term consequences of stress exposure. This is particularly true for social stressors. Here, stress exposure during the early active phase (i.e. the morning in day-active humans) is much more detrimental than stress at later times, promoting increased appetite and weight gain.
Two important suggestions are derived from these experiments: (i) Stabilizing endogenous circadian rhythms – e.g. by daily routines and sufficient and regular sleep times – may shield our body (and brain) against the detrimental effects of repeated stress exposure. (ii) Moreover, if a stressful encounter is just unavoidable – be it a business meeting or a trip to the local public administration – consider scheduling it to the afternoon or early evening. At this time your hormonal stress axis is much less sensitive to stimulation. This may help you to keep cool and also should weigh less on your long-term metabolic debt count.
Our work at the University of Luebeck aims at unraveling how the genetic circadian clocks in different tissues interact with each other in regulating physiological homeostasis and the physiological response to external stimuli such as stress or an obesogenic (i.e. weight promoting) environment. Studying the molecular mechanisms underlying this whole-body circadian clock network regulation will help us to find new ways of counteracting chronodisruption as a hallmark of modern 24-hour societies. Our experimental data suggest that, even though there is pressure to devote maximum time and energy to business demands, ignoring biological timing and sleep hygiene may on the long run rather damage than promote professional persistence and performance.