You’ve probably heard fitness gurus preach time and again that in order to start losing fat you need to be consuming fewer calories than you are burning. And, if you’re like most, you’re probably trying to get your body into fat burning mode either by going on an even stricter diet (and hoping all the weight won’t come back once you inevitably return to normal eating) or by trying to burn some extra calories during your workouts by manipulating your training program and adding in more cardio.
Indeed, training and nutrition are two of the primary factors we need to look at whether we’re trying to build muscle, lose fat, or gain strength. While these two factors get most of the attention, there is one additional critical factor to consider if we want to shed fat and perform at our best. It is perhaps the most overlooked factor contributing to a leaner, more muscular physique, and it is also one that, if neglected, could ultimately jeopardize your body recomposition efforts.
And that factor is sleep.
How Lack of Sleep Effects Your Body
In 2013 I moved to Portugal where I studied for 10 months as part of a university exchange program. There were a lot of exchange students like me that year, and one of them, a Brazilian fellow, became a good friend of mine. He wasn’t really the sporty type—I wasn’t able to make him come to the gym with me even once for all those months. In fact, I’d often go to his house and I’d find him lying in bed, eating pizza and watching TV. So, you can imagine he wasn’t exactly into health and fitness.
When I met him in the beginning of the first semester, even though he had an admittedly unhealthy lifestyle like most 21-year-olds, his metabolism alone was quick enough to hold off the damage that he was doing to his body. Gradually that started to change. Soon, he started gaining a few pounds a month and, as you might guess, those pounds added up over time until one day a few months later when winter passed, he literally couldn’t get into his summer shorts.
The weird thing was, he said he wasn’t eating more than he used to back at home in Brazil. Exercise wasn’t in the equation either way. The only thing that had changed was now that he didn’t live with his parents and he was at last his own man, he started sacrificing sleep and staying up late to work on university projects or to watch TV.
Could this have been the cause for his slow, but steady, progression to a dad bod? You bet.
Sleep Deprivation Influences Your Caloric Intake
Even though my friend was eating more or less the same meals as back home, one thing that led to his unexpected weight gain was the fact that he failed to account for the late night snacks that pushed his body into caloric surplus. He always had snacks like chips, crisps, or sweets lying around. You know how this scenario this goes down: you’re watching your favorite TV series after a long day at school or work and you decide to have a little bit of crisps or just one piece of chocolate, and soon enough you’re reaching out for more until you’ve unwittingly had 200-300 extra calories just before bed.
Think this is exaggerated? Think again.
In a systematic review and meta-analysis of human intervention studies assessing the effects of partial sleep deprivation, scientists found that the sleep deprived (less than seven hours of sleep per night) tend to consume 385 kcal more compared to the control condition.1 For most people, increasing intake by 385 kcal daily is significant enough to cause serious weight gain. So, if my friend was consuming 300+ extra calories each night then it’s no wonder why he suddenly started gaining weight.
But his increased caloric intake is just the tip of the iceberg. In order to reveal the full consequences of sleep deprivation we need to go deeper.
Sleep Deprivation Influences Your Hormones
We now know that my friend, like many other sleep deprived folks, was consuming a considerable surplus of calories and ultimately that is what led to his weight (and fat) gain. But we still don’t know what it is about sleep deprivation exactly that causes us to increase our caloric intake.
One explanation could be linked to the fact that when we’re sleep deprived, we’re awake for a longer period of time. Our bodies generally burn more calories when we’re awake than when we’re asleep so it’s plausible that our bodies signal our brains to seek out more food to compensate. But as the above-stated study reveals, there was no significant change in total energy expenditure or resting metabolic rate as a result of not getting enough sleep. Meaning the sleep deprived folks had increased their total caloric intake without increasing the amount of calories they burned.
Why do we crave more food when we don’t get enough sleep? A University of Chicago study among 12 healthy males in their early 20s found that sleep deprivation is associated with an increase in ghrelin levels and a concurrent decrease in leptin levels.2 Ghrelin, also known as the hunger hormone, is basically the hormone that signals your brain that you are hungry. Leptin, on the other hand, is the hormone that signals that you are full.
This study suggests that, when sleep deprived, we tend to feel hungrier and less full. This explains why the sleep deprived folks averaged a 385 kcal caloric surplus, compared to people who get to bed on time and get enough sleep.
Another issue related to sleep deprivation is the type of foods we crave when we don’t get enough shut-eye. Studies present conflicting results, so we need more research on the subject. But that being said, some studies do suggest that when sleep deprived, we’re more likely to lean toward unhealthy high-carb, low-protein foods.3
This is bad news particularly because most of these unhealthy high-carb foods are loaded with sugar, and according to another University of Chicago study, sleep deprivation also negatively affects how our bodies handle glucose.4 More specifically, the study reveals that sleep loss is associated with impairments in glucose metabolism, including insulin sensitivity, and notes that “it is possible that insulin resistance could also promote increased adiposity and weight gain.”
Sadly, the cascading negative effects of sleep deprivation don’t end here.
Sleep Deprivation Affects Your Brain
As if sleep deprivation didn’t cause enough trouble by screwing up our hormones, it turns out that it also messes with our brains. According to yet another study, sleep deprivation decreases activity in the critical decision making regions of the brain, the frontal cortex and insular cortex, and amplifies activity within the amygdala, the reward region of your brain that makes you seek out high-calorie foods.5
It’s no wonder being sleep-deprived has been compared to being drunk. In a sleep-deprived state you lack impulse control and you’re more likely to just reach out for those tasty cookies in front of you.
But there’s more.
Sleep Deprivation Affects Your Workouts
As you probably know, having more muscle helps you burn more fat. Apart from helping you burn more calories during workouts, this happens because increasing your muscle mass leads to a higher Basal Metabolic Rate (BMR)—the amount of calories you burn in a 24-hour period if you were to do absolutely nothing.
That’s all good and well. Sadly, sleep deprivation can ultimately lead to less muscle, and thus more fat. Scientists found that sleep deprivation can lead to decreased protein synthesis meaning that your body is capable of building less muscle when you’re on low sleep.6 Another point stated in the same study is that, in case of sleep deprivation, there’s a marked increase in cortisol, the catabolic hormone. That means that not only will you build less muscle, but you can also experience muscle loss.
Finally, less total sleep means less slow wave sleep and during slow wave sleep is when your body releases the most growth hormone. The increased levels of cortisol don’t help much either, further decreasing the release of growth hormone, and again leading to less muscle—and more fat.
How Much Sleep Should You Be Getting?
By now sleep deprivation probably sounds like a downward spiral to hell and hopefully you understand exactly how it can bring your muscle building and fat loss progress to a quick halt.
But enough depressing studies and statistics. By this point, you’re probably just wondering how much sleep you actually need. In 2015 the American Academy of Sleep Medicine (AASM) and Sleep Research Society (SRS) developed a consensus recommendation for the amount of sleep you need to be getting every night in order to function optimally: 7 to 9 hours per night.7 Of course, the exact amount of sleep needed varies depending on the individual, but it’s safe to say that 7 hours per night seems to be the bare minimum and that those who work out probably need a bit more.
That being said, I’d like to leave you with a few tips for higher quality sleep:
- Don’t look at screens (TV, desktop, or mobile devices) for two hours before bed
- Sleep in complete darkness
- Use earplugs if you live in a noisy environment
- Go to bed and wake up at the same time each day
Get Your Sleep
Sleep deprivation can be a serious problem both for your health and for your body composition. The decrease in average sleep duration in the U.S. has occurred over the same time period as the increase in obesity and diabetes.4 Make sure to get your fair share of quality sleep every night to keep your body fat percentage low and your health in check.
1. HK Al Khatib, SV Harding, J Darzi and GK Pot (2016). The effects of partial sleep deprivation on energy balance: a systematic review and meta-analysis. European Journal of Clinical Nutrition (2016), 1–11.
2. Spiegel, K. (2004). Brief Communication: Sleep Curtailment in Healthy Young Men Is Associated with Decreased Leptin Levels, Elevated Ghrelin Levels, and Increased Hunger and Appetite. Annals of Internal Medicine, 141(11), p.846.
3. Markwald, R., Melanson, E., Smith, M., Higgins, J., Perreault, L., Eckel, R. and Wright, K. (2013). Impact of insufficient sleep on total daily energy expenditure, food intake, and weight gain. Proceedings of the National Academy of Sciences, 110(14), pp.5695-5700.
4. Kristen L. Knutson, PhD, Karine Spiegel, PhD, Plamen Penev, MD, PhD, and Eve Van Cauter, PhD (2007). The Metabolic Consequences of Sleep Deprivation. Sleep Med Rev. 2007 Jun; 11(3): 163–178.
5. Stephanie M. Greer, Andrea N. Goldstein & Matthew P. Walker (2013). The impact of sleep deprivation on food desire in the human brain. Nature Communications 4, Article number: 2259
6. Dattilo M, Antunes HK, Medeiros A, Mônico Neto M, Souza HS, Tufik S, de Mello MT (2011) Sleep and muscle recovery: Endocrinological and molecular basis for a new and promising hypothesis. Medical Hypotheses 77, 220–222.
7. Consensus Conference Panel, Nathaniel F. Watson, MD, MSc, Moderator, M. Safwan Badr, MD, Gregory Belenky, MD, Donald L. Bliwise, PhD, Orfeu M. Buxton, PhD, Daniel Buysse, MD, David F. Dinges, PhD, James Gangwisch, PhD, Michael A. Grandner, PhD, MSTR, CBSM, Clete Kushida, MD, PhD, Raman K. Malhotra, MD, Jennifer L. Martin, PhD, Sanjay R. Patel, MD, MSc, Stuart F. Quan, MD, and Esra Tasali, MD (2015). Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society. Sleep 38. Jun 1; 38(6): 843–844.