Obesity and Physical Inactivity: The Relevance of Reconsidering the Notion of Sedentariness
So, having already made one change to the structure of the research review and looking at more than paper at a time, I’ve decided that that approach is confusing, it also makes the titles and permalinks screwy which, as any good Internet marketer knows, is bad for SEO. So moving forwards, I’m going to go back to only looking at a single study at a time (but still in less detail) but do them more often.
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Chaput JP, Tremblay A. Obesity and Physical Inactivity: The Relevance of Reconsidering the Notion of Sedentariness. Obes Facts. (2009)2(4):249-254.
The population statistics of most countries of the world are indicating that industrialization and computerization have been associated with an increase in sedentariness and more recently with a significant shift from healthy weight to overweight. In general, this change in the overweight/obesity prevalence is attributed by health professionals to suboptimal diet and physical activity practices. However, recent data raised the possibility that excess weight gain might also be the outcome of changes imposed by our ‘24-hour’, hectic lifestyle. Parallel to an increase in body weight, one has observed a reduction in sleep time and an increase in knowledge-based work (KBW) that appear as a growing necessity in a context of economic competitiveness and globalization. Sleep and cognitive work both exert a trivial effect on energy expenditure and may thus be considered as sedentary activities. However, their respective effect on energy intake is opposite. Indeed, an increase in the practice of the most sedentary activity, i.e. sleep, is associated with a hormonal profile facilitating appetite control whereas KBW appears as a stimulus favoring a significant enhancing effect on food intake. Television viewing is another example of sedentary activity that has been shown to increase the intake of high-density foods. These observations demonstrate that the modern way of living has favored a change in human activities whose impact goes well beyond what has traditionally been attributed to a lack of physical exercise. Therefore, we will need to reconsider the notion of ’sedentariness’ which includes several activities having opposing effects on energy balance.
My comments: Traditionally, the treatment of obesity has focused on two primary components which are dietary intake and energy output; there are both good and bad reasons for this that I’ll address in a future article or research review but the fact remains that those two factors tend to represent the things we have the most control over (e.g. we can’t do anything about genetics, or about what mom did while she was pregnant). I tend to think I’ve spent enough time on the site talking about diet that I needn’t get into it here so I’m going to focus on the activity end of things.
Now, as discussed in Metabolic Rate Overview as well as The Energy Balance Equation, there are 4 primary components on the energy out side of the energy balance equation: Basal metabolic rate (BMR), Thermic effect of Food (TEF), Thermic Effect of Activity (TEA) and Spontaneous Physical Activity/Non-Exercise Activity Thermogenesis (SPA/NEAT). The two I’m going to focus on relative to today’s research review are the last two, a recent separation whereby formal exercise and all other daily activities have been separated out.
Now, traditionally obesity treatment has also focused on the exercise end of the equation but there have always been a few problems with this. Perhaps the largest relative to what I want to talk about today (and I’ll be doing a very thorough article at a later date on this so please be patient in the comments) is that the amount of exercise that is or can usually be done is actually fairly trivial compared to the rest of the day.
That is, the hour someone might spend engaged in exercise is still pretty small compared to what’s happening the other 23 hours of the day. And, as many have found out by using tools such as the Bodybugg/GoWear Fit, small changes during the majority of the day (e.g. getting up every so often during the day to walk around at work for 8 hours) end up having a far larger impact on daily energy expenditure compared to the hour of exercise they might do. As many have also found, being very inactive for those same 8 hours (e.g. jockeying a computer desk) doesn’t burn many more calories than laying in bed.
Which is all a very long introduction to today’s paper which looks in some detail at two of the major changes in modern life that contribute to our overall ‘inactivity’ during the day: sleep and what the researchers decided to call knowledge based work (KBW). Sleep is fairly explanatory but, by KBW, they are referring to things such as school, jobs involving thought and concentration and even potentially video games. Basically anything where you’re sitting on your ass for most of it but having to involve your brain rather intently.
And while both activities fall under the heading of ‘inactivity’ (in that you burn very few calories during either of them), they actually end up having not only different but diametrically opposed effects on the potential for weight gain and obesity. Basically, just saying that ‘inactivity causes weight gain’ is simplistic and, as it turns out, incorrect. The type of inactivity is relevant here.
In the case of sleep, and there has been a tremendous amount of literature in this regards in recent years, it’s turning out that sleep deprivation does rather horrible things not only for overall health but for weight gain and obesity risk. Sleep deprivation tends to decrease leptin level (removing the tonic ‘block’ that leptin exerts on appetite/hunger) and raise level of ghrelin (the only hormone shown to directly stimulate hunger in humans). I discuss both hormones in detail in the series on Hormones of Bodyweight Regulation but the end result of such a shift will be an increase in hunger/appetite along with a negative effect on calorie partitioning. Hormones such as cortisol, thyrotropin hormone (involved in thyroid function) and others are also impacted positively by sufficient sleep and negatively by too little sleep. As the authors state:
Hence the beneficial effect of sleep go well beyond its role in the restoration and maintenance of tissue structure and function…Despite the low energy cost of sleep, population studies have repeatedly shown that a short average duration of sleep is associated with excess body weight…recent research evidence showed that an average nightly sleep of 7-8 h in adults is associated with a lower risk of obesity, type 2 diabetes, coronary heart disease and all-cause mortality.
Hard to get much clearer than that. Basically, despite the unbelievably low caloric cost of sleeping (usually around 1 cal/min), the indirect impact is massive in terms of the benefits for getting enough sleep and harm for not.
Moving on to the other topic of the paper we get to KBW, again referring to activities such where you’re sedentary but engaged in large amount of mental activity. The paper mentions work, school, even video games and computer ‘chatting’ (you Facebook people know who you are) and other related activities as potential examples of KBW.
And, as you might expect, while similarly sedentary like sleeping, the impact of KBW on appetite and body weight regulation tend to be rather negative. The brain, unlike skeletal muscle, can’t use fat for fuel and studies have shown that intense thinking can screw blood glucose levels; this is relevant as some work shows that falling or lowered blood glucose can stimulate hunger. And usually for junkier food (which is invariably found in large amounts in the work space).
Studies have found that even short bouts of intense KBW can increase total energy and fat intake as well. In one, for example, females were assigned to a 45-min mental work session and then provided an ad-lib buffet. Despite only burning 3 extra calories during the task, the KBW group ate 229 more calories compared to a group that only rested. In the long-term, this adds up big time.
And while it hasn’t been studied directly, the researchers question whether such things as video games and Internet chatting might be similarly stimulatory of appetite (and let’s be honest, is anybody eating non-junk food when they play WoW). The amount of time spent watching Tv is a known risk factor for obesity in children, increasing the intake of high-energy density tasty foods; whether this is related to the same mechanism as KBW such as work or studying is currently unknown.
Finally, it’s worth mentioning that Tv and computer involvement is often done late at night and this can interrupt sleeping patterns (the constant influx of photos into the eyes makes it harder to get to sleep). So there’s a potential double whammy.
Summing up: So that’s that, a quick look at two different types of ‘inactivity’ that end up having diametrically opposed effects on the risk for weight gain, obesity and other health risks. Those two are sleep, perhaps the most sedentary activity of all (unless you get lucky) and knowledge based work (KBW).
Getting sufficient sleep, something that is becoming harder for many to do (by choice or life requirement) is a key aspect of not only overall health but limiting obesity risk. With good sleep hygiene and habits (e.g. get off the computer earlier, go to bed a bit earlier every night), this is at least within the realm of some people’s control.
The issue of KBW is tougher as folks have to make a living and many jobs involve long hours of KBW (often in an environment where nothing but crappy food is available). Clearly quitting your job and sleeping all day, while attractive, isn’t an option for most. At least being aware that intense bouts of KBW can screw with blood glucose and appetite may help with finding strategies around it.
Keeping better snack foods handy to stave off hunger following such work efforts would be one strategy, I have to wonder if a small amount of carbohydrate during the activity would help to stabilize blood glucose. Perhaps Gatorade can come up with a ‘Conference Call Gatorade XXXtreme’ version of their drink. Yes, XXXtreme with three X’s.
So do you or trainers you know ascribe adequate sleep for people you train? When I worked with Martin, it was purely diet/training.
Very interesting, and I’d like to see other related studies. Anecdotally, I’d have to say that my best studying is done while exercising (walking outside or on the treadmill). It seems counterintuitive that exercising helps the focus, where I would expect blood glucose to be diverted to the working muscles instead of the brain, but that’s my experience. Does exercise metabolize blood glucose faster than it uses it?
I also think of eating small sugar doses like jelly beans (or milk/sugar in my coffee?). I notice that my reaction to intense KBW feels similar to emotional stress; it turns on the munchies. Getting enough protein in the day does help, though.
Are there other things one can do to keep blood glucose levels high while doing intense KBW?
Not sure what you mean by ‘prescribe’? Adequate sleep is important for all kinds of things, not just what’s in todays article. If someone is having issues, it’s one of many things to look at. Also keep in mind that this is another place where there is a huge difference in people actively monitoring caloric intake and those that aren’t. This is just another variable that tends to promote overeating/weight gain, it won’t magically make it occur in a deficit or when folks are consciously controlling calories. But that’s not most people.
RG: Exercise does different things to blood glucose depending on intensity. At high intensities, blood glucose can actually go up as mobilzation is higher than use. At moderate intensities, it tends to stay fairly stable. It gets complicated fast depending on overall diet, training status, gender, etc.
Thanks! I use low to moderate intensity for my training status. At intense levels, my entire focus is on exercising, but maybe I should throw in short bursts of that. The stretch break, or doing a lap around the building; it’s hard to tell how much of the effect there is just “clearing your head” but I often go to a 45 minute study – 15 minute “run an errand” balance. Just pacing while trying to read a difficult paper seems to help, but a moderate “can talk but still a noticeable exertion” feels like the sweet spot for focus.
Maybe I should take a break every half hour from studying to do some burpees in the law school library.
Greetings All,
After the quote: “…an average nightly sleep of 7-8 h in adults is associated with a lower risk of obesity, type 2 diabetes, coronary heart disease and all-cause mortality.”
You say: “Hard to get much clearer than that.”
These are associations; they might not be causal. Perhaps overweight people sleep poorly? It could be the weight interferes with their breathing. Or maybe poor diet leads to both obesity and to poor sleep.
Thanks for the blog.
Brent: While a good point, there has been data where sleep duration has been manipulated with the end-results (e.g. effects on hormones) measured. And it’s the duration of sleep causing the hormonal perturbations, not the other way around.
I’d also note that this can become a feedforwards loop, for example, obesity can cause sleep apnea and the inability to sleep well causes further problems.
But the impact of short sleep on a variety of parameters has been measured in an intervention (not just correlational sense) type of study and the impact is there.
I normally sleep only 6 hours per day. I find it interesting how the right amount of sleep can ward off (or minimize) so many health risks. I guess I really have to establish a healthy sleeping pattern.
Would saltines be a good snack for KBW as long as you are wise with your portions? Most of their calories come from carbs, is it too slow acting though?
“The brain, unlike skeletal muscle, can’t use fat for fuel…” What about ketones? Could a lack of post-KBW excess caloric intake be one of the mysterious magical properties of a ketogenic diet?
Scott: Ketones, while fat derived, are not fat and I doubt it, in that order. Becuase keto diets aren’t magical.
Waffle: Here’s the thing it doesn’t really matter. The bloodstream only holds 5-10 grams of glucose and just about anything ranging from a small piece of candy to a piece of fruit to everything in-between will work sufficiently to normalize/stabilize blood glucose if it’s low. Pick whatever you like to eat but won’t overconsume.
Gotcha. I wasn’t referring to keto diets as being “magical” in a performance sense, but more in terms of compliance.
I know that sitting on an excercise ball instead of a chair assists greatly with core muscles and thus posture, but can it help to counter some of the negative effects of sitting at a desk for 8 hours a day? Does utilising these core muscles instead of just sitting on a chair increase caloric output at all?
The study you quoted on ad lib feeding and KBW – the exercise used in that study was perceived as a stressor by the women (as shown by higher cortisol levels vs the control condition), and that’s a significant confounder. KBW is not the trigger for overeating, stress is. I don’t think this was made clear enough in the article.
Is there a link between non-stressful KBW and higher calorie intakes in a similar fashion? I don’t think so.
Could chatting and WOW contribute to overeating in a similar fasion? Perhaps if they are perceived as stressful events.
You ever had a raid go wrong?
More seriously, it’s a good point and I’m quite sure that it is the relationship of stress with the types of KBW being discussed here that is at issue.
Lyle – do you have any good resources to help with the sleep portion of the equation?
I should stop doing things like reading and playing videogames. Drinking beer doesnt require much thought, I guess that is my next main mission.
very interesting review, Im way too obsessive to make my reading and playing make me fat. Drugs help as well.
NOOOOOOOOOOOOOOOO!!!11 WHy did I read this. My blood sugar levelssss noooooo…
Chris: Sleep is very complicated and I cannot claim to be an expert in sleep dynamics. Certainly the first thing to deal with is sleep hygiene (your habits at sleep time) and there is a ton of stuff on the web about this. But avoiding computer/light in the eye, stimulants, having a set sleep time a whole bunch of stuff goes into helping people sleep better.
When that doesn’t work, there are numerous supplements that can help with sleep ranging from melatonin to 5-htp to taurine to all kinds of stuff in-between. The problem is that nothing works for everyone and there is often trial and error involved. This is because sleep can get messed up by a variety of different mechanisms and the different products all hit different pathways.
When that fails, drugs are an option, something I truly know nothing about.
Marclee: Ha ha.
Lyle – interesting post. thank you. i’m not sure i get your meaning when Scott questioned your statement that the brain can only use glucose, not fat. in a ketotic state the brain uses more ketones and less glucose than on our usual diet. but of course you know that; was your reply kind of shorthand?
i hope i don’t stay awake worrying about it……………
I was merely making a rather pedantic correction regarding his disagreement with what I wrote in the article. And the brain still uses some glucose (~25% of it’s full requirements still come from glucose even after full blown keto-adaptation). And as anyone who’s done a ketogenic diet, blood sugar can still get crashed. Does that happen during KBW? I have no idea. Most of the studies that suggest that ‘ketogenic diets impair brain function’ look at them during the first week or so, long before adaptation has had time to take place.
You mentioned video games such as WoW increasing caloric intake, however I have put many hours on that game and always seem to not be hungry or eat while I am playing. I have friends that also play that say the same thing happens to them, not eating for hours at a time while engrossed in gaming.
Will: Do you know what a generality/generalization is?