Great news, my fellow Sleep Challengers – we made it to week 3 of the Sleep30 Challenge by Sleep Number and we’d love for more of you to join us! I’m so happy to report that the Challenge’s sleep tips have worked their magic and I’ve finally kicked my jet lag! This week we’ll focus on the relationship between food and exercise to your sleep. Read my conversation below with Dr. Peter Attia and learn why we all tend to crave candy rather than kale when we haven’t had enough Zzzs…
Katie Couric: Do you think most folks understand how interconnected diet, exercise, and sleep are? Tell us a little bit about this connection…
Dr. Peter Attia: No, I think most people do not appreciate this. Certainly, I did not appreciate this until probably the last six or seven years (and my entire existence is supposed to center around living longer and living better!). It would take a lot of time to go into this in great detail, but briefly, when a person’s sleep is deficient, and this can be deficient in duration and consistency of timing or deficient in various stages of sleep, it can often result in metabolic changes that alter nutrition intake. In other words, it can increase your likelihood of eating the wrong foods, but more importantly, it can drive suboptimal fuel partitioning, which is just a fancy way of saying you are more likely to store the foods that you eat as fat and less likely to access your fat stores when you exercise. With respect to exercise, the biggest detriment that incomplete or inadequate sleep would have on exercise is probably in reducing one’s drive to exercise.
That’s really fascinating. Tell us more about this relationship between sleep and the battle to lose weight…
There are probably several factors that drive weight gain and the difficulty of weight loss in the setting of sleep deprivation. Experimentally, it has been demonstrated that depriving people of sleep produces insulin resistance, and insulin resistance itself makes it very difficult to lose weight because it comes along with hyperinsulinemia (high insulin) which makes it harder to utilize existing fat stores. Also, inadequate sleep drives suboptimal appetitive behavior, which means you are more likely to make worse food choices than you would be if you are well rested. It also reduces your drive to exercise, and it might even raise cortisol levels. All of these factors–insulin resistance, poor eating habits, less exercise, higher cortisol levels–would all promote fat accumulation, which is exactly what you don’t want if you are trying to lose weight (or prevent weight gain in the first place).
I think we can all relate to the idea of giving into food cravings when we’re exhausted! Can you talk more about what’s influencing these choices from a physiological standpoint?
This is a complicated question, but I think at a summary level, I could say the following: A number of studies have demonstrated that inadequate sleep down regulates leptin levels (a hormone secreted by fat cells), which may play a role in satiety. It also up-regulates ghrelin (a hormone secreted by the stomach), which leads to greater appetite, and it has been experimentally found that people will eat additional food calories the day following just one night of partial sleep deprivation. In a nutshell, sleep deprivation comes down to down-regulating or up-regulating hormones that push you in the direction to eat more. Furthermore, the prefrontal cortex of the brain, which is the part of the brain that keeps our hedonic desires in check, tends to be impaired by sleep deprivation. In addition to just making poor decisions in general when we are sleep deprived, we are also more likely to make poor decisions about food, specifically.
What about alcohol and caffeine…how do they affect our quality of sleep?
Alcohol has a very clear detrimental effect on sleep. While you may fall asleep faster due to alcohol’s sedative effects, it has been demonstrated experimentally that as little as 1 to 2 drinks in the hours before bedtime will significantly reduce REM sleep and generally replace it with light sleep and greater periods of wakefulness throughout the night. Caffeine plays a role in sleep because the effect of caffeine is to block adenosine, which can be thought of as the sleepiness signal, in the brain. Adenosine rising is one of the factors that physiologically drives sleep. It’s also important to understand that caffeine has a half-life of 6 hours, so if you drink a cup of coffee at 4 pm, half of that caffeine will still be in the brain at 10pm.
Let’s talk about exercise. We know it’s good for our health, but why is it so good for our sleep?
As I alluded to above, one of the main forces driving sleep is the accumulation of adenosine and perhaps nothing more than exercise leads to the accumulation of adenosine. Therefore, the more active we are, the more adenosine we accumulate, the more we increase our drive to sleep. Parenthetically, the other things that play an important role in sleep drive are cortisol levels, which we want to see decline as we get closer to bedtime, and melatonin levels, which we want to see rise. In summary, optimal sleep is had when adenosine levels are high, melatonin levels are high, and cortisol levels are low.
What’s the best time to exercise for better sleep?
If there is an optimal time of day to exercise proven to improve sleep, I’m not sure I know of it. I do think there is better insight as to when you should try to avoid exercise, and that would be right before bed. In order to initiate sleep, your core body temperature must drop about 2 degrees Fahrenheit (think about trying to fall asleep in a cold room vs. a hot room). And post-exercise, your body temperature can be elevated for a few hours which could disrupt sleep.
Do you think we’re starting to better understand the relationship between lack of quality sleep and how it relates to chronic disease?
Yes, I think people like Professor Matthew Walker at UC Berkeley have done an incredible job in elucidating the causal relationship between sleep deprivation and chronic disease, specifically, atherosclerosis, cancer, and Alzheimer’s disease. Even the World Health Organization now recognizes the impact of sleep deprivation on these diseases. For a more detailed look at these links, and for an overall robust discussion on sleep, please see my interviews with Dr. Matthew Walker, in three installments: part 1, part 2, and part 3. You can also see Matthew’s recent talk at TED here.
What’s your own sleep routine? As a busy and successful physician, how are you able to make sure you follow your own sleep advice?
Like any behavior, it requires deliberate attention and a conscious desire to prioritize it. In that sense, I would think of sleep the way one would think about exercise or nutrition. If you want to eat well, you have to spend more time planning your meals. If you want to exercise, first and foremost, you have to make the time to do it. For me, the key to getting a good night sleep is as follows:
1. I try to disconnect from electronics at least two hours before bed. If I am looking at them, I do so through the lens of a blue light filter (both a filter on my phone or laptop, but also glasses that filter out blue light).
2. I try to limit food intake at least 2, and ideally 3, hours before bed and avoid alcohol if at all possible (and if I drink, limit to one; more than one really destroys my sleep quality).
3. I keep my bedroom as cool as possible. I try to keep air temperature at about 65 degrees, and I use a cooling pad on my mattress that keeps the mattress at about 55 degrees.
4. I keep the room as dark as humanly possible and sometimes that requires even wearing a silk eye mask to eliminate any additional light. This is especially important in hotels which always seem to have too many annoying lights.
5. I go out of my way to keep a very consistent schedule of both bedtime and wake up time, both on weekdays and weekends, including my frequent travel. On the west coast I keep an “an early to bed, early to rise” schedule of about 8:30 or 9 pm to 4:30 or 5 am, while on the east coast I keep more of a 11 pm to 7 am schedule. I think the details of this are less important than the principle of similar time to bed and wake up as often as possible.