How your insomnia is making you fat (part 1 of 3)

Picture of Dr. Jen Kerns

Dr. Jen Kerns

Sleep is a critical biological process that allows brain energy stores to rebuild and allows for the clearance of waste products (including beta amyloid, the accumulation of which is implicated in the development of Alzheimer’s Disease) through the “glymphatic” system. If you don’t believe me when I tell you that sleep is as important to life as water, you have only to read the macabre scientific studies from the 1980s in which total sleep deprivation in rats led to death within a matter of weeks.

Over the past decade or two, the intersection between sleep and obesity has gotten increasingly complex. A simple Google search on “sleep and obesity” today yields over 85 million results, and sleepiness has been suggested as the new “6th vital sign” that should be checked by healthcare providers. If you’re an American, a quick visit to the CDC’s website can tell you how prevalent inadequate sleep is in your region of the country. In my hometown of Bethesda, Maryland, a DC suburb, 32% of adults report short sleep duration (less than 7 hours per night). I am one of those adults: I have been struggling with early awakenings, or “maintenance insomnia,” for years now – waking in the middle of the night several times, sometimes getting up for the day as early as 3am when unable to go back to sleep after tossing and turning a bit. (One middle-of-the-night awakening is normal if you get back to sleep, but more than that isn’t.)  I typically get between 6 and 7 hours of sleep on a normal night, and usually wake multiple times within that 6.5 hours, so my sleep architecture is somewhat fragmented, too.  A personal quest for better sleep (mostly driven by my intense interest in delaying my own potential onset of Alzheimer’s Disease, but also by the wish to just feel better) led me down the rabbit hole of sleep research. In next week’s post I’ll talk about the various strategies I’ve adopted in an attempt to improve my own insomnia, but this week I’d like to scratch the surface of how short sleep and/or disrupted sleep promotes weight gain and obesity.

I heard the basic physiological effect of inadequate sleep on bodyweight described elegantly in a podcast interview of Dr. Matthew Walker, a sleep researcher at Berkeley and author of the bestseller “Why We Sleep.” He explained that for the vast majority of human evolution, we were hunter-gatherers who did not have organized agriculture, let alone the industrialization of food and a 24-hour convenience store on every corner. Our bodies evolved to intentionally create a physiologic state of wakefulness if we were starving. This wakefulness had the effect of allowing us to go travel farther to find food more effectively (after all, if we fell asleep while we were starving, we’d be more likely to continue starving and eventually die). He explained that the opposite is true, as well — that just as when our bodies are experiencing starvation, we will naturally experience insomnia, when our bodies are experiencing insomnia (or intentionally disrupted or short sleep), our brain misinterprets this to mean we must be starving. This triggers a myriad of mechanisms designed to increase our appetites and make us more likely to eat.

One such mechanism is a decrease in serum leptin levels that occurs in response to inadequate sleep. Leptin is a hormone produced by adipocytes (fat cells) that, when high, signals that the body is well fed, and when low (as naturally occurs when there are few fat stores to produce it), signals that the body is starving and acts to lower satiety and lower energy expenditure. This basically makes you eat more and move less. Not only do leptin levels drop with poor sleep, but acutely inadequate sleep (meaning just a single night of poor sleep) leads to an increase in the potent hunger hormone ghrelin, which is released primarily by the stomach. (Anyone ever thoroughly enjoy a breakfast at a greasy spoon diner after a night out drinking and subsequent poor sleep? Check.) Researchers not only found these changes in appetite regulating hormones that promote overeating, but also found that participants with an average nightly sleep of 7.7 hours were the thinnest, and participants with less sleep than that had significantly higher BMIs.

I personally believe good quality sleep for 7-9 hours per night (in adults) is actually more important for overall health and the maintenance of a healthy bodyweight than is exercise, though certainly, I am a huge fan of each! If you don’t even know how much you’re sleeping, the first step is awareness: start keeping a sleep journal and record your bed and wake times to estimate it each day (or look at the data from your Apple Watch, Fitbit, or Oura ring). If you, like me, are getting less than 7 hours of sleep on any given night and/or have fragmented sleep, join me next week for part 2 of this 3 part series and I’ll get into the nitty gritty of potential solutions and the various changes I have personally made in my own quest for better sleep.

Please leave me comments below, feedback (positive or negative!) and topics you’d like for me to cover in upcoming blog posts would be great. I’m all ears!

Until next week – sleep tight!




Leave a Reply

Your email address will not be published. Required fields are marked *