Stress, Sleep and Social Jetlag: The Obesity Epidemic's Psychosocial Side

Femke Rutters, PhD, MSc


October 19, 2015

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Good morning. My name is Dr Femke Rutters, and I am with the Department of Epidemiology and Biostatistics at the VU Medical Center in The Netherlands. Today, I would like to talk to you about the role of stress, sleep, and social jetlag in the development of obesity and metabolic diseases in the general population.

There's nothing new in saying that we have an obesity epidemic on our hands. About 1 in 3 people in the world are obese or overweight. This has dramatic consequences for our healthcare system, because obesity puts us at risk for type 2 diabetes; hypertension; and metabolic diseases, such as heart disease and dyslipidemia.

The pathophysiology of obesity is really simple: It's caused by eating too much and moving too little. We just have to deregulate the energy balance by putting it back in balance, or by losing some weight—then everything will be better.

We all know that it's difficult to get on a diet and to stick to it. The results are disheartening: Only about 1 in 3 people lose weight on a diet. The rest keep a stable weight, or even gain weight, while dieting. When you look at the long term, the results are even more disheartening. About 1 in 100 people keep the weight off that they lost while dieting.

So why is it so difficult to stick to a diet and maintain energy balance?

Genetics play an important role. A sedentary lifestyle is also a factor in our environment. It is really easy to remain sedentary with our increased use of cars and escalators.

However, I want to talk to you today about psychosocial factors that have an influence on obesity. It comes down to three S's: stress, sleep, and social jetlag.


Stress has known negative effects on health.

Stress is defined as everything that is a threat, either "real" or "imaginary," to homeostasis. An example of "real" stress would be a lion escaping from the zoo and seeing you as lunch. An example of "imaginary" stress would be giving a talk, such as this presentation. Although it is not physically harmful, it is still stressful.

A higher risk for obesity is one of the negative effects that stress has on health. In 2011, Jane Wardle and colleagues[1] published a needs analysis that showed that there is a positive association between weight gain and stress.

There are several pathways through which stress results in weight gain. One of these is the endocrine pathway, described by Professor Björntorp in his hypothesis.[2] He says that owing to overactivation of the hypothalamic-pituitary-adrenal (HPA) axis, you get increased levels of cortisol, which results in weight gain, predominantly in the visceral area.

But there is also a behavioral pathway.

In one of my own studies, we showed the effect that stress had on eating.[3] After giving people lunch (so that they were satiated—not hungry anymore), we subjected them to a stressful task, and afterward presented them with a nice tray of snacks. This included chocolate and licorice—it was a Dutch study, after all.

The results showed that people who were stressed ate more, even though they weren't hungry—a factor already well known in the study of obesity.


A less well-known psychosocial factor of obesity is sleep. The first evidence that there is an association between sleep and obesity is an ecological one.

Studies have shown that in the past 50 years, we went from sleeping about 8.5 a night to sleeping only 7 or less. This happened at around the same time period as the obesity epidemic.

So there are already a few epidemiologic studies that indeed show that "short sleep" (which means about 6 hours or less) has about 50% chance or higher of leading to obesity and weight gain.[4]

In one of my own studies, I showed a more direct association by looking at adolescent teenagers—a period of life when children decide for themselves how many hours they are going to sleep.[5] The children who decided to sleep less were the children who gained the most weight.

In addition to sleep quantity, sleep quality is also important. In two large studies in which we subjected people to nights of disturbed sleep, we woke them every hour or every 2 hours and saw that indeed, the energy balance was disturbed and the endocrine factors involved in weight regulation were altered.[6,7,8]

Sleep is important, and is one of the main factors that can influence weight and the obesity epidemic.

Social Jetlag

One factor that is relatively new in obesity research is social jetlag—a term that is very narrowly associated with the circadian rhythm, meaning sleep timing.

We all know that as we go through the day, we have a variable rhythm. For example, in the morning, your cortisol is high, so that you can get up and get to work, and then in the evening it goes down, so that you can relax and go to sleep. Disturbance of that rhythm—for example, when you have jetlag or when you work the night shift or you do shift work—has negative effects on the endocrine and behavioral mechanisms involved in obesity regulation and weight regulation.[9]

One of the less well-known factors is social jetlag, which basically means the difference between your internal rhythm and the external rhythm that is forced on you by your environment.

For example, let's say I am a night owl. I produce and am at my best in the evening. Some people are really early birds and get up at the crack of dawn. But when society puts you in a situation where you are not an early bird but you still have to be at work at 7 AM, then a dysregulation between the two rhythms happens, which we call "social jetlag." During the weekends, when I don't have to work and am left to live on my own rhythm, I end up producing a mini-jetlag when I switch back to society's rhythm. After every weekend, when I return to work, I have a mini-jetlag of a few hours.

This has shown to be a bad thing in several studies. One big Internet-based study asked respondents questions about when they go to bed during the week and on weekends, and the results showed that indeed, social jetlag is associated with a higher body mass index (BMI).[10] In one of my own studies, I showed that it is indeed associated with changes in behavior—people become less active. There are also changes in endocrinology, so people have a higher HPA axis.[11,12]

Overall, what I want you to take from this message is that stress, sleep, and social jetlag are three important factors involved in obesity, and maybe—although you can't do much about it yet—you can ask your patients, in addition to their metabolic status, about the condition of their psychosocial status.

Thank you.


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