In last weeks post I wrote about a study that showed sleep restriction (4 hours a night) promoted weight gain. In the study, the authors hypothesized that the weight gain was due to increased ghrelin levels and late-night eating (1). This study triggered my Alice In Wonderland and sent me down a research rabbit hole. Let’s face it, we are fighting an uphill battle in the obesity fight. As humans we are wired to eat and a lack of sleep is only making that worse. Recent research has shown a correlation between a lack of sleep with increased consumption of sugary, caffeinated beverages (2). In the study, Short and sweet: Associations between self-reported sleep duration and sugar-sweetened beverage consumption among adults in the United States, they analyzed data from 18,799 adults who self reported sleep durations and completed two 24 hour dietary recalls. Out of the 18,799 adults, 13% slept five hours or less. The group of people who slept five hours or less had a 21% increased in sugary caffeinated beverages. Granted, the lack of sleep could have been a contributor to the increased consumption of caffeinated beverages. And usually most caffeinated beverages contain sugar so that could account for the increased intake. But I don't think that is the reason why. I believe a lack of sleep is rewiring our brain causing us to crave sugary foods and there are studies to back this claim.
The first study, Sleep curtailment is accompanied by increased intake of calories from snacks, showed a lack of sleep contributed to increased snacking. Eleven healthy participants took part in two 14-day laboratory stays where they were given access to as much food as possible with either 5.5 hour or 8.5 hour sleep schedules. The goal of the study was to measure and compare calories consumed from meals and snacks between the two sleep schedules. By the end of the study the scientists found that the sleep-restricted group had consumed significantly more calories from snacks, and had consumed a higher percentage of carbohydrates before bed (3). From these results the scientists concluded that a sleep-restricted schedule in an obesity-promoting environment may cause the excessive consumption of calories from snacks, but not meals(3).
This is important to highlight because, in last week's post, subjects in a different study saw increased meal frequency when restricted to four hours of sleep per night. The subjects in this study did not report increased meal frequency, but consumed more snacks. .In addition to measuring calories consumed from snacks, the scientists also measured the subjects ghrelin (hunger hormone) levels. However, there was no difference between the groups. This lack of ghrelin could explain why the meal frequency did not increase. But if the hunger hormone (ghrelin) didn’t increase, then why did they find a significant difference in snacking between the sleep schedules? To answer this question I had to do some more digging, and luckily I was able to come across a study that helped me answer this question.
The study, Sleep restriction leads to increased activation of brain regions sensitive to food stimuli, included 30 subjects who took part in two different sleep schedules. The first phase required the subjects to sleep four hours per night while the second phase required them to sleep 9 hours. Each phase lasted six days and on the last day a functional magnetic resonance imaging (FMRI) was used to determine how the subjects brain reacted to food. The results showed increased neural activity in the response to food after sleep restriction (4). Also, they found increased activation in brain regions that are responsible for reward and pleasure in the sleep restricted group (4). This increase in please seeking behavior and increased neural activity in response to food could be the reason why we consume more calories from snacks on the days we don’t sleep.
In my experience as a personal trainer I have found that the majority of people know how to eat healthy and know that they need to exercise. However, they can’t adhere to these guideline because they lack the discipline and focus that is needed. I believe this discipline is lacking due to insufficient sleep. In order to adhere to a healthy lifestyle in an obesity promoting environment sleep is paramount. As you can see from the studies above, a lack of sleep will reduce your ability to say no to foods which will increase your meal frequency and snacking. This lack of sleep combined with increased meal frequency and snacking is what has caused the obesity epidemic. So put down the phone, turn off the television and get some rest.
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. http://doi.org/10.5665/sleep.2792
Prather AA, Leung C, Adler NE, Ritchie L, Laraia B, Epel ES. Short and sweet: Associations between self-reported sleep duration and sugar-sweetened beverage consumption among adults in the United States. Sleep Health. 2016 Dec;2(4):272-276. doi: 10.1016/j.sleh.2016.09.007. PubMed PMID: 28393097; PubMed Central PMCID: PMC5380400.
Nedeltcheva AV, Kilkus JM, Imperial J, Kasza K, Schoeller DA, Penev PD. Sleep curtailment is accompanied by increased intake of calories from snacks. Am J Clin Nutr. 2009 Jan;89(1):126-33. doi: 10.3945/ajcn.2008.26574. Epub 2008 Dec 3. PubMed PMID: 19056602; PubMed Central PMCID: PMC2615460.
St-Onge MP, McReynolds A, Trivedi ZB, Roberts AL, Sy M, Hirsch J. Sleep restriction leads to increased activation of brain regions sensitive to food stimuli. Am J Clin Nutr. 2012 Apr;95(4):818-24. doi: 10.3945/ajcn.111.027383. Epub 2012 Feb 22. PubMed PMID: 22357722; PubMed Central PMCID: PMC3302360.