Want to know how much sleep you can get by on? Simple. Have kids.
My 3-year-old and 3-month-old have shown me have far I can push my sleep-deprived body. There is a difference between getting by and optimally performing, however. Just because I can get by doesn't mean I should.
I cringe every time I hear the phrase “I’ll sleep when I’m dead” and fortunately, that reaction is becoming more common. Over the past 5–10 years, sleep has been getting a lot more attention. While we may, for the most part, be past the days of “sleep is for weaklings,” proudly acknowledging how little we average on a nightly basis, sleep still falls far down the priority totem pole for many people.
As a physical therapist, I discuss sleep with all of my patients. While it is possible to physically recover from injuries and surgery without good sleep, it is more difficult.
Gaining a better understanding of sleep has positively impacted my patients and the outcomes they have achieved. The knowledge has also improved my performance. I know share sleep research with my patients and colleagues during residency and continuing education courses.
Here are some of the less talk about ways sleep influences our health and careers.
How Sleep-Deprived Are You?
There are two primary categories of sleep loss in the research. Sleep restriction (SR) refers to a partial disturbance of their normal sleep-wake cycle. This is the milder category of sleep loss. (Tuesday after the Superbowl)
Sleep deprivation (SD), meanwhile, refers to extreme cases of sleep loss, where both quality and quantity are significantly affected. (First few weeks after a child is born)
It is important to understand the duration of SD as it will impact the time it takes to recover and normalize your sleep. Unfortunately, we cannot bank our sleep, and sleeping in late on a random Saturday will not erase chronic sleep debt.
All of the impacts of sleep I am about to cover typically occur in a state of SD. SR may lead to some changes as well, but they are typically milder and can be quickly reversed with a good night of sleep or some coffee.
Reflect on your daily routine. Which category do you fall in? Is sleep a priority? It should be.
Sleep Influences Our Hormones
When hormones are mentioned, people often think of emotions, but hormones control many functions in our bodies. Hormones are responsible for building muscle (testosterone), controlling our blood sugar (insulin), healing (cortisol), and feelings of hunger (leptin). All of these hormones, and many more, are influenced by sleep.
Have you ever noticed an increased desire to snack when you are hungry? Your leptin levels — the hormone that tells your brain you are full — are lowest when you are sleep deprived. This causes you to crave more food. The desire for snacking intensifies when we are tired.
Our cortisol levels increase when we are in a state of sleep debt. While cortisol — the stress hormones — is necessary for healing, excessive levels can be harmful. Most of my patients are already in a stressed state due to injuries, comorbidities, medications, and surgery; layering in sleep deprivation is only worsening the situation.
Hormones levels can be influenced by other stressors as well, such as arguments, marital challenges, and job satisfaction. Once again, sleep deprivation feeds a positive feedback loop of harm
Sleep modifies the effects of our diet as well.
Our insulin sensitivity and glucose tolerance decrease when we are sleep deprived. Essentially, we are more susceptible to blood sugar spikes. Chronic sleep deprivation can contribute to a reduction in insulin sensitivity, a precursor to diabetes. Bad news.
As you can see, our sleep duration and quality can significantly impact the effectiveness of dietary interventions. Whether you are trying to lose fat or build muscle, lack of sleep will make it harder to achieve your goals.
Sleep is Needed to Build Muscle and Lose Fat
Losing weight and building muscle are both challenging. They require disciplined eating and exercise. Looking for an added challenge? Throw in sleep deprivation and you will be hard-pressed to achieve desired results.
Scales can be deceiving. Dropped pounds do not always mean fat loss. A study looked at the influence of sleep on the type of weight we lose. It took two matched groups of people and controlled their diet and exercise. They all completed the same exercise plan while cutting their daily calories by 10%. The difference was the amount of sleep they received: 8.5 versus 5.5 hours. At the end of the study, each group lost the same amount of weight, but where they lost the weight differed. The weight the people in the 8.5 hours group lost was 50% fat and 50% muscle. For the 5.5 hour group, the weight loss was 20% fat and 80% muscle.
The amount of sleep we receive changes how our metabolism works. Similarly, research shows it is more challenging to build muscle when we are sleep deprived. During deep sleep, our body uses fat stores for energy and stimulates muscle growth. Sleep deprivation causes the reverse. We break down muscle for energy and leave the fat stores alone.
The scale will say your diet is working, but the mirror will be less kind if you are lacking sleep.
Sleep is Needed for Performance
Sleep can be broken down into five stages and each serves a specific function. For example, we build memories during slow-wave sleep, including motor memory. Sleep is not only necessary for remembering information, but for improving movement skills such as your golf swing or playing the piano. The amount of sleep deprivation matters.
A single night of poor sleep will not cause your muscle to deteriorate or your skills to vanish. Research suggests, however, sport-specific skill execution, submaximal strength, and muscular power decline with short-term sleep restriction.
Fewer than seven hours of sleep can impair alertness, reaction time, memory, and decision-making. Research shows sleep restriction causes heightened levels of sleepiness, depression, confusion, and poorer overall mood states as well. When sleep deprivation becomes chronic, athletic performance suffers greatly and it becomes more difficult for athletes to recover.
Greater total sleep loss results in poorer overall mood states, increased fatigue, sleepiness, and confusion, decreased vigor and liveliness, heightened depression, and decreases in logical reasoning and decision making. The speed and accuracy of cognitive, auditory, and memory tasks all suffer. Sleep deprivation will dramatically worsen our effectiveness at our jobs, school, and training.
So, in summary, when we in sleep debt, we struggle to recover and heal, our thoughts and memories significantly decline, our metabolism suffers, and we are hungrier. The solution is simple: sleep more.