Social Jetlag and Metabolic Risk

by Dr Sven Hansen

A November study in the Journal of Clinical Endocrinology and Metabolism shows in a study of 447 adults that when we free run our biological clock over weekends (non work days), we suffer from lower HDL, higher triglyceride, greater BMI (body mass index) and larger waists. In short we develop metabolic syndrome, which is known to lead to heart disease, diabetes, obesity, high blood pressure and inflammation.

What this study shows is that 84% of adults will sleep in on the weekend when free of work obligations. This is called social jetlag (SLJ) – the weekend sleep-in. Unfortunately, those who sleep in over the weekend are triggering a cascade of metabolic problems that will have both short and long term effects on our health.

I have been reviewing literature on the biological clock all year and have come to a very clear conclusion. The genetically controlled circadian clock has to be aligned with the light-dark cycle of your location for optimal health and performance.

The way to align your inner clock with your environment is through smart use of light signals (zeitgebers). Yes, we do need about 7.5 hours of sleep AND it is essential to time, enter and exit sleep in the right way.

Avoid all screens for at least an hour before bed. Strong blue light that comes from TV, computers, tablets and phones will reset your clock by 12 hours. Essentially you are simulating sunrise as you prepare for bed. It causes sleep disruption, resets your circadian clock and compromises your hormone levels. Darker rooms, cooler temperatures and yellow light facilitates the “flop” into sleep at the right time for your body. At least 69% fail on this count.

Ideally, we want to wake up at about the same time each day and in time to experience directly the blue light of down (before sunrise). This is a great time to do your stretches, relaxation and take a walk outside and “flip” to alertness. Some bright light during the middle of the day might also be good.

Again, don’t sleep in this weekend. It increases your risk of being fat, diabetic, ineffective and dead.