Circadian Rhythms: Bulletproof Your Biology

Have you ever stayed up late and slept in on the weekend, only to have to wake up early for work on Monday morning? This pattern is known as “social jet lag, and night owl-types tend to be more negatively impacted because their preferred later sleep/wake schedule is more in contrast with standard weekday work hours.

For example, if you sleep 12am-6am on weekdays, but sleep 2am-10am on weekends, then you’ve more or less shifted your body over 3 time zones (without the travel). As such, not only will waking up on Monday morning be painful, but people with these rhythms are also more likely to be overweight (and with a higher BMI comes a much greater risk for health problems).

Let’s boil it down to 3 main reasons:

1. Adolescence trains a bad habit. Human biological systems take ~20 years to fully develop, so teenagers actually thrive on a later night owl rhythm; staying up until midnight and sleeping until 9am actually fits teenage physiology quite well. In our youth we can become accustomed to these types of later patterns and the habits formed here often carry far too late into adulthood. As young, active, hormonally-charged organisms we often “get away” with bad habits re: food and sleep, which subsequently act as the drivers for weight gain and premature health decline in our 20s & 30s.
2. Internet & smartphones. It started with TVs and desktop computers, but we can all now stare blankly at a bright screen in the comfort of our own beds, with an endless flow of entertainment options at our literal fingertips. The advent of these technologies has also made people more accessible than ever, making for longer work hours and social schedules.
3. 24-hour everything. This goes hand-in-hand with the advent of the internet, but it’s worth specifying. We now have 24-hour access to almost anything: Streaming TV shows/movies, food delivery, gaming, the list goes on. Nighttime is no longer just for sleeping; if you want to be nocturnal, it’s easy to do so.

We have created a world where going outside is no longer a necessity. Many of us now view physical activity as a cumbersome burden. Why walk when I can Uber? Why go to the store when I can have my groceries delivered? Why cook when I can get a hot meal brought to my doorstep? Year after year we’re building in conveniences that make us less and less human: Less physical activity, less time outdoors, less true social interaction and less connection to the natural rhythms of the sun.

The data is quite clear that shift workers have worse health outcomes than the rest of the population (much greater prevalence of diabetes, obesity & metabolic syndrome), but this is an obvious and extreme example.

Regarding standard diurnal rhythms, the majority of circadian research thus far has been done on mice (and is quite compelling in regards to the importance of not eating food after dark). But let’s focus on human studies. Overall, the research paints a fairly dramatic picture regarding night owl-types and those with social jet lag:

• Poorer sleep quality and duration
• Higher association with smoking, drinking and less physical activity
• Higher risk of depression and depressive symptoms
• Greater risk and severity for developing bipolar disorder or ADHD
• Higher likelihood of developing binge eating disorder
• Impaired cortisol patterns and higher incidence of insulin resistance
• Increased prevalence of type-2 diabetes and high blood pressure
• Greater body fat and incidence of obesity

While there is still lots of research to be done, it’s already clear that when you attempt to shift your biology away from that of your natural environment, everything becomes an uphill battle. For those who are interested, this research paper succinctly summarizes the human research to date.

While there is no way to make unhealthy lifestyle habits magically beneficial, regular physical activity can mitigate some of the consequences.

For example, if you routinely go to the gym in the evening, you can train your body to better adopt a later rhythm (provided your sleep cycle is also conducive to this shift). Again, the research does not show that this prevents potential long-term health consequences (relative to people who are tuned to earlier rhythms), but physical activity can seemingly help blunt some negative symptoms in night-owl types.

However, if you rarely exert yourself physically and live with offset circadian rhythms, this is a surefire recipe to promote weight gain, to develop mental health issues and to speed up physical decline.

German for “time-giver”, zeitgebers are environmental cues that synchronize human biological rhythms to a 24-hour cycle. As mentioned earlier, the most important of these cues is light, and secondary zeitgebers include things like food, caffeine, physical activity and socializing.

If you’re struggling with body weight or health concerns, adjust your morning to include the following:

• Wake up with the sun and get bright light on your face ASAP (ideally go outside)
• Have an early-morning coffee (but none in the afternoon)
• Eat early and make breakfast your biggest meal of the day
• Be as active as possible with the bulk of activity in the morning hours

To bring things full-circle, in the evening follow-up your morning habits with these behaviours:

• Finish dinner as early as possible, with no late snacks
• Eliminate intense activity and stress after dinner
• Dim lights and limit screens after dark
• Be in bed early enough to give yourself a chance at 8 hours of quality sleep

Again, the human research here is young and the mechanisms are not yet fully understood, but correcting misaligned circadian rhythms will result in better sleep, which we know drives the bus for human health processes and immunity.

Parenting is a special kind of sacrifice, and you’re a superhero. Kids come first and while sleep can be tough to come by for the better part of a decade, the points above give you a great blueprint to follow once you again have the means to set your own schedule.

In the meantime, accumulate sleep whenever you can, stay as active as possible, and don’t eat after dinner.