Sunday, August 25, 2013

Is your bedtime hurting your diet?

There have been several studies describing the association between obesity and poor sleep. However, no study to date has been able to explain whether sleep deprivation causes weight gain, obesity causes sleep problems, or why these relationships occur. Recently, Andrea Spaeth and her colleagues at the University of Pennsylvania conducted a controlled study to ask:
Does sleep deprivation cause weight gain… and how?

To do this, they found 225 healthy adults (age 22-50) who have regular sleep patterns (e.g., they sleep between 6.5 and 8.5 hours per night, they go to bed between 10pm and midnight, they wake between 6am and 9am, and don’t habitually nap). Each participant provided information via questionnaires, participated in a physical examination, and provided a blood sample. These participants were then assigned to different conditions, some of which required them to undergo a series of sleep restricted nights (between 2-5 nights), and some of which were control conditions. During sleep restriction, participants were allowed to go to bed at 4am, and were allowed 4 hours in bed.

The study took place over the course of 12-18 days, depending on the number of sleep restriction days in the participant’s condition. All participants slept in the laboratory, and were provided with plenty of different food and drink options throughout their stay. Patients were allowed to eat and drink freely as long as they didn’t interfere with the study assessments.  The research team was interested in whether sleep restriction caused greater caloric intake or greater weight gain than the control condition.

Not surprisingly, sleep restricted participants ate more food, opted for food that was high in fat content, ate later in the day, and gained more weight during the research study than the control participants. These findings were greater for male participants than female participants.

These findings are helpful to me in a lot of ways. First, this study confirms that multiple nights in a row of poor sleep will make it harder to maintain healthy eating habits… and a healthy weight as a result. However, until now, some theories have hypothesized that these associations were driven by physiological differences in the way food is processed under sleep deprivation conditions. Remember a few weeks ago when I told you that sleep deprivation can cause temporary insulin resistance? Because of my busy life, I can’t necessarily resolve to never lose sleep, so these negative health-related consequences would, theoretically, be inevitable. Fortunately, this study shows that we have more control over the outcome of our sleep loss. In this study, sleep deprivation led to weight gain for specific behavioral reasons. Sleep deprived participants chose high fat foods, ate more if it, and ate those foods during times when they would otherwise be sleeping. These are all behavioral explanations for the weight gain, thus we can fight back.

Unfortunately, this study didn’t address the physiological theories directly. It is still possible, if not likely, that there are differences in how our body metabolizes food when we are tired. Furthermore, this study focused primarily on pretty severe sleep restriction. Even I don’t sleep 4 hours per night for 5 days in a row. So, further research needs to be conducted to extend these findings to more “normal” variations in sleep deprivation.

Either way, when it’s Thursday night and you’ve had a long week, you are more likely to opt for fattier foods, eat them later at night, and eat more of them. Now that you know, change the habit. When you’re tired, choose the healthier option. When you're up late, don't snack. Don't let the negative health consequences of sleep loss snowball.

Spaeth, A.M., Dinges, D.F., & Goel, N. (2013). Effects of Experimental Sleep Restriction on Weight Gain, Caloric Intake, and Meal Timing in Healthy Adults.  Sleep, 36(7), 981-990. doi: 10.5665/sleep.2792

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