August 3rd, 2020

Does weight gain affect sleep, or does sleep affect weight gain?  

As the age-old conundrum goes, what came first: the chicken or the egg?  We see so many studies that focus on the effect that poor sleep has on weight, but what if it’s the other way around? Weight gain can have a detrimental effect on sleep habits, potentially creating a vicious cycle that is hard to break.  

 So, if poor sleep leads to weight gain, then what does weight gain do to your sleep? A new 2020 study published in the American Journal of Human Biology suggests that weight gain leads to poor sleep in C. elegans worms (we know, it’s worms, but stick with us here). This finding, if corroborated in human studies, could be groundbreaking. 

We know that for humans, lack of sleep can lead to appetite increases, insulin resistance, high blood pressure, and other hormonal dysregulation [i].  In theory, this means that poor sleep habits could potentially predispose someone to weight gain. In fact, sleep is an important tool in nutrition assessment and is often something we work on in one-on-one nutrition counseling.  

Where this new study differed was in looking at sleep; researchers looked differently at the relationship between sleep and metabolism. They turned off the gene that controls sleep in C. elegans worms, so the worms could still eat, breathe, and reproduce, but could not sleep. With this, they found a decrease in ATP levels, a measure of energy [ii]. Because of this, they postulated that sleep is a way to conserve energy. Without sleep, less energy is conserved. 

Another interesting finding came about when researchers hypothesized that the release of fat stores (aka fat burning!) “is a mechanism for which sleep is promoted” and that without the sleep gene, the worms were unable to sleep because they couldn’t “liberate their fat stores.” [ii] Here we have a very novel hypothesis: it may not be the lack of sleep that contributes to obesity, it’s the fat stores themselves that regulate sleep patterns.  With another gene mutation that helped them “free” their fat stores, the worms were able to sleep once again [ii]. Does this mean that the more fat stores we have, the more signals can get crossed when we try to sleep? Research suggests that this could absolutely contribute. 

At the end of the day, literally and figuratively, what does this mean for us? It is always a good idea to try to improve your sleep habits through good sleep hygiene and routines. With this research in mind, we can add that losing some of those extra lbs may be more helpful for a restful night’s sleep than we used to think. 


  • [iKnutson, Kristen L. “Does inadequate sleep play a role in vulnerability to obesity?.” American journal of human biology : the official journal of the Human Biology Council vol. 24,3 (2012): 361-71. doi:10.1002/ajhb.22219
  • [ii] University of Pennsylvania School of Medicine. “Link between obesity and sleep loss: Energy conservation may be a major function of sleep, according to new study in worms.” ScienceDaily. ScienceDaily, 22 April 2020.