Jun 11 2012

Sleep and Weight

Recent evidence suggests there is a link between sleep quality and weight control – poor sleep correlates with risk of obesity. The possible causal connection goes both ways. Obesity increases the risk for sleep apnea and other conditions that may interfere with sleep, such as back pain. Recent studies also suggest that sleep deprivation increases appetite and decreases energy ependiture. A recent review summarizes the evidence:

On this basis, the present review examines the role of sleepcurtailment in the metabolic and endocrine alterations, including decreased glucose tolerance and insulin sensitivity, increased evening concentrations of cortisol, increased levels of ghrelin, decreased levels of leptin and increased hunger and appetite. It will be discussed how sleeprestriction may lead to increase in food intake and result in greater fatigue, which may favour decreased energy expenditure.

All of the hormonal factors listed above would tend to increase hunger and fat storage and decrease satiety. Fatigue also decreases energy output. Resulting weight gain may further worsen sleep, leading to a vicious cycle.

A new study adds another element to the mix. Researchers looked at 23 healthy subjects over two sessions, one with normal sleep and one with sleep deprivation. They then exposed them to various food choices while in an fMRI scanner. They found that the sleep deprived subjects had decreased activity in their frontal lobes while making food choices.

This is a small and preliminary study, and fMRI data is very tricky to gather and analyze reliably. It also hasn’t been published but was presented at a scientific meeting. If we assume the results are valid, however, the study tells us two things. The first is that there is a difference in brain activity in the sleep deprived vs well rested state. This is not surprising, as optimal brain function is known to be highly sensitive to sleep deprivation. The other question the researchers were interested in, however, is what part of the brain is involved with food choices and sleep deprivation. It’s possible that there could have been increased activity in the more primitive centers of the brain that drive hunger, but that is not what they found.

The frontal lobes are involved in executive function, making complex strategic behavioral choices, such as which food to eat. We may be faced with many motivational factors simultaneously, such as hunger, the allure of our favorite foods, and also the desire to be healthy. The executive function of our frontal lobes is needed to balance these factors and come up with a final decision and act upon it. Avoiding tasty but unhealthful food takes a lot of mental energy, and those subjects who were sleep deprived had decreased mental energy. This means they are more likely to give in to their more basic urges rather than override them with their executive function.

Added to the prior research, and again assuming these results hold up, we can see that sleep deprivation causes a significant shift in the balance of factors that determine our behavior. We are more hungry and less able to modulate that hunger.

What do you do if you are trapped in this vicious cycle? It seems that we need further research to explore various approaches, but there are some common sense and evidence based approaches that will likely help. The first is to address sleep quality and duration. If that is the primary problem (such as sleep apnea) then the sleep disorder needs to be properly diagnosed and treated. Many of my patients have terrible sleep but do not volunteer that information or list it as a complaint, but when asked they relate having serious sleep problems. They simply did not consider it to be part of whatever complaints they were presenting with. If you have any sleep issues a reasonable first step is to see it as a problem and discuss it with your physician. They may want to order a sleep study and may be able to diagnose a specific problem.

Even without a specific underlying sleep disorder, many people can use improved “sleep hygiene” – basic methods of improving sleep quality and duration. These include things like not eating right before bed, avoiding caffeine, especially in the evening, and allowing for a sufficient winding down time before getting into bed.

In order to address the fatigue part of the equation, regular exercise is advised. Exercise has many documented health benefits in any case, and there is some research to support the conclusion that exercise improves sleep.

Because we are dealing with a complex interconnected physiological response, it is probably necessary to address many factors at once – overall eating habits, sleep quality, exercise, and any underlying conditions that may be affecting the quality of sleep or the ability to engage in physical activity. Further the research suggests that we need to consider the fact that maintaining healthy lifestyle habits is difficult. It takes a lot of mental energy, and there are factors that can decrease our mental energy and leave us vulnerable to poor decisions. It just takes a moment of sleep-deprived weakness to ruin a whole day of healthful eating.

This, perhaps, might be the biggest challenge, from both a personal and public health perspective. Part of the strategy of addressing the rising rates of obesity might be to make healthful eating decisions easier to make (requiring less of that frontal lobe mental energy). Some have suggested, for example, that perhaps it’s not a good idea from a public health perspective to ask every fast food customer if they want to supersize their order. We can preserve individual choice, but make the more healthful choices the default, low mental energy, pathway of least resistance. Make unhealthy choices take more mental energy and effort.

We also may want to consider the role of rationalization. This is where I think fad diets and many dieting products fail – they provide the illusion of eating healthy and make it easy to rationalize unhealthy behavior. Those low-fat cookies still have a lot of calories, but the “low-fat” on the label is very effective at short circuiting our executive function with denial and rationalization. Having restaurants print calorie content, for example, is likely an effective way to combat denial, and at least will help those who are paying attention.

We definitely need more research in this area to identify the optimal strategies for making healthful eating more common and to reverse the obesity trends in our society. I do think that taking a physiological and neurological view is helpful – identifying all the various factors that ultimately contribute to caloric intake and energy expenditure.

13 responses so far

13 thoughts on “Sleep and Weight”

  1. SARA says:

    In my opinion, it’s issues like this that are crucial to tackling the problem of obesity. Obesity is mostly a behavioral (or choice, if you will) issue, driven by a lot of factors we don’t really understand.
    Sleep is one of them. But there are others.
    People want it to be about foods. More protein, less fat, more of some vitamin, etc. But for the vast majority of people, it’s about calories and our inability to limit ourselves to necessary number of calories.
    Why is it so hard for people to limit ourselves is the question. We need more research on why.

  2. wetchet says:

    @SARA. I agree 100%. The most important part of the summarized results above “…and increased hunger and appetite”. But the diet industry will focus on the the following “endocrine alterations, including decreased glucose tolerance and insulin sensitivity, increased evening concentrations of cortisol, increased levels of ghrelin, decreased levels of leptin”. Having dealt with an eating disorder myself, and having rampant overweight-ness and obesity in my family tree, I have seen first hand that the primary issue is diet and exercise, yet most people simply cannot seem to accept that. Much easier to believe you have “increased cortisol and decreased leptin”, take a supplement and wait for a miracle to occur.

  3. bluedevilRA says:

    This is very interesting research. It’s been discussed many times on this blog, but the “calories in, calories out” approach to weight loss is really the best way (and the EBM way). Fad diets, magic pills, etc just will not cut it. Unlocking the neuroscience behind bad eating habits could yield additional psychotherapies to help change the way we approach food.

    I also believe the printing of calorie information on foods is a simple and effective strategy. It just makes the information more accessible. Regardless of how one feels about the politics of the “soda ban” in NYC, I think it could potentially help people think twice before going back for a second soda. Also, I wonder if we could modify soda, fast food, etc to have bigger labels with the calorie information. Sort of like what they do with smoking. Cigarettes in the UK have huge font warning labels saying “smoking seriously harms you and others,” “this could kill you,” etc. So maybe bigger calorie labels that explain how much activity someone would have to do to burn off the number of calories in a 20 ounce soda, a big mac and fries or whatever else?

    Also, I’ve seen quite a few “there’s nothing wrong with being overweight/obese” stories recently. There’s the Healthy At Every Size initiative and there was a cnn opinion piece by a bioethicist. One of the points she argued was that very thin people could be just as much of a health burden as very large people. Perhaps. But there are more obese people. Either extreme is bad, but our current problem is that of increased weight, not decreased weight. I think this topic puts health care workers in a delicate position of having to address the health issues associated with increased weight, while at the same time making it clear that this has nothing to do with a judgement about the patient’s appearance or character.

  4. Kawarthajon says:

    This diet/obesity issue raises important questions about whether we truly have a free will, or if our behaviour and choices are basically determined by our genetics and our automatic response to environmental stimuli. My guess is the later. I don’t think that we have a whole lot of choice in our behaviour, beliefs and the daily choices we make. If we did have a choice, more people would be able to resist the gluttonous food that is more and more available to us these days and avoid getting overweight/obese. People who marketed food would have to respond to people’s free-will choices and market healthier foods. In reality, though, people know that certain foods are really bad for them, but they still eat them over and over again despite that knowledge. Food is like a drug and once you get addicted to a certain type of food, it is very hard to change your habits to avoid that food.

  5. daedalus2u says:

    Sleep is a high NO state. There is a characteristic drop in blood pressure during sleep, but this characteristic dropping does not occur as much in people who are obese or who have hypertension, they are called “non-dippers”.

    It is during sleep that much of the “maintenance” that physiology does happens. That is when memories are consolidated in the brain, when mitochondria biogenesis in muscle and other tissues mostly happens.

    My hypothesis is that the high NO of sleep is a global signal for repair and maintenance to be turned up. If sleep occurs during a low NO state, then I would predict that the sleep would be less “refreshing”, in that there is less repair and recovery.

    Essentially all degenerative disorders are also associated with poor sleep and even insomnia. Chronic fatigue is characterized by non-refreshing sleep. The only reason that sleep is “refreshing”, is that physiology occurs during sleep that causes it to be refreshing.

    Sleep apnea is a low NO state, and drugs that affect NO physiology affect sleep apnea. For example viagra makes sleep apnea worse. The way that viagra works is by inhibiting a phosphodiesterase that cleaves cGMP, the product of sGC when activated by NO. Disruption of this control system, likely causes feedback inhibition of NO generation, and would decrease pathways mediated by NO which are not mediated through the sGC-cGMP pathway. Triggering of breathing is mediated by NO, but not through the sGC-cGMP pathway.

  6. kikyo says:

    “allowing for a sufficient winding down time before getting into bed.”

    I think learning how to manage this is going to be important. I know many people, including myself, who simply do not have sufficient winding down time that also allows for a large amount of sleep. I don’t get any time to myself until after 11pm, but I have to be up by 7am most days. I find myself staying up later than I should because it’s the only time I have to do certain things that I enjoy and to relax on my own. I’m not sure how to address that without the current ability to adjust my work schedule and home responsibilities.

  7. ConspicuousCarl says:

    Novella said:
    winding down time before getting into bed.

    I find that this applies mainly to mental winding down. I can do some hefty exercising and then drop like a rock, but watching TV or playing video games will keep me up.

    The frontal lobes are involved in executive function, making complex strategic behavioral choices,

    It would be interesting to see how much, if any, our impulsive/heuristic functions also decrease with fatigue. As bad as they are normally, they are still (in theory) better than randomly guessing and have room to get worse.

    Rikki-Tikki-Tavi said
    -There are a lot of appearently useless rules. E.g. for a time she couldn’t eat citrus fruits. She still may not eat mint.
    -She is losing weight, but with the miniscule amounts of food she may eat, that’s really no wonder
    (-She keeps telling me how great the diet is)

    I have heard that fad diets can temporarily get people to eat less due to the novelty factor of avoiding certain things, but then people soon get bored with eating bunless hamburgers. I wonder if the structured dynamic nonsense in this particular plan keeps the nonsense interesting for longer. That way, instead of getting tired of a wacky diet and “failing”, you can think “success, now I move on to stage 3!”

  8. happy humanist says:

    Data set of one: I started eating better via the help of a doctor-recommended nutritionist and lost two dress sizes. Then, about 6 months later, I was diagnosed with sleep apnea and began using a CPAP machine. While my eating habits didn’t change, I lost one more dress size surprisingly in the weeks after.

    This is such a complicated issue, but hormones do matter very much.

    And, in my personal experience, sleep apnea is severely underdiagnosed. Many friends are snorers (like me) and nap in the afternoons or evenings as we watch a movie or tv, like I used to. Some have CPAP machines and don’t use them (find them uncomfortable and cumbersome), and some refuse to see a problem. And, many, of course, can’t afford the sleep studies and machines without good health insurance (I was lucky as insurance paid for all of my expenses).

    If you have a friend or family member who snores and/or sleeps in the day, please make sure they see a doctor.

  9. SimonW says:

    “The possible causal connection goes both ways”, and the correlation might also be explained by underlying metabolic disorders, or even dietary deficiencies, which affect both one’s weight and one’s sleep.

    But I’ll never know as it is behind a pay wall….

  10. SARA says:

    @conspicouscarl. There are studies that show that we have lower ability to make decisions (particularly ones that go against an automatic desire or habit) when we are fatigued.

    @Kawarthjon. I struggled with the idea that there is no choice myself a couple of weeks ago. I decided that we a brain that evolved from a totally automated processing center to one that allows limited choice making. We have executive function, but I think we mostly don’t use it. We train ourselves into lots of automatic habits because our brain only allows us limited amounts of willful choices. I base my thoughts on the studies I refer to above. Anyway this idea helps me sleep at night.

  11. HHC says:

    Since when does the New York Major think it is his executive function to monitor New Yorkers’ dietary indiscretions?

  12. ConspicuousCarl says:

    SARA on 11 Jun 2012 at 7:28 pm

    @conspicouscarl. There are studies that show that we have lower ability to make decisions (particularly ones that go against an automatic desire or habit) when we are fatigued.

    Sure, but it’s the non-particular category I wonder about. All of the studies I have seen like to point at how our high-level executive whatchamacallits are affected, but there is no mention (that I recall) of exactly what the effects are on those primitive intuitive judgments. It might be out there. I only just now realized that I had not thought or heard of it.

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