 Okay, Marian Rosenberger is about to step up if I'm correct here. Yeah, she's next on the list. So, Mary Rosenberger is our only postdoc on the presentation today. She works closely with Bill Haskell. She's interested in using technology for both measurement and providing feedback about physical activity behavior, and in particular, the challenging assessment of sedentary behavior. She gave an oral presentation on some of these data at American Heart's Epi and Prevention Meeting in Atlanta back in March of this year, and she was subsequently selected to present the same talk at the best of AHA specialty conferences at Scientific Sessions 2011 that will be in Orlando this November. Thanks for sharing it with us. We're so privileged. Thanks, Christopher. I don't actually have a lot of data, but I'll tell you what I found. So, sedentary behavior is kind of a hot topic right now, and as I talk about it, if you want to take advantage of the standing tables, I don't mind if you make that transition while I'm talking. Usually when I start to talk about it, people get a little antsy. So, in 2008, Russ Payt published this statement, and it was basically saying that sedentary behavior is just as important as physical activity when looking at health outcomes. And since then, there's been a lot of research on the effects of sedentary behavior, so increased risk for metabolic syndrome, increased cardiovascular disease risk factors, and recently it's published that increased mortality from all causes. So, it's associated with longer bouts of sedentary behavior. The definition has been a difficult thing to pin down, so it seems like sedentary behavior is sort of self-explanatory, but you can define it in terms of energy expenditure. So, one met is sitting quietly, and there's some consensus building around 1.5 met as the upper limit of sedentary behavior energy expenditure. You can define it in terms of activities. Now, is sleeping sedentary behavior probably not because it's a health behavior? Well, sedentary behavior is not a health behavior. And it's standing part of sedentary behavior. When you're standing, you're not expending much energy, but it's probably not included in sedentary behavior. And you can also define it in terms of motion. So, we use accelerometers, which measure motion to measure sedentary behavior. The research that Christopher was referring to was my work with the actigraphic accelerometer. It outputs counts, so more counts equal more motion, and my research determined that 100 counts is the separation between sedentary and not sedentary activity. Neville Owen is a leading sedentary behavior researcher, and he came up with this definition, that both sitting and low levels of energy expenditure make up sedentary behavior. Another definition would be muscular inactivity that came out about the same time. I have my own way of thinking about it that I'd like to share. Sitting on your duff, I think sort of encompasses all these definitions. So, why the interest in sedentary behavior now? One reason is that we're a very sedentary society, the most sedentary that we've ever been in evolution. We have better measurement tools for sedentary behavior, so accelerometers have come to the point where we can actually define when people are sedentary and when they're not objectively. A lot of studies in the physiology of sitting have started to come out, and they're really starting to pinpoint a detrimental metabolism that kicks in when you sit down and gets worse the longer you sit, and so it might be its own physiology. It's not just a lack of exercise, but the sitting in particular. And it offers a new area for intervention, so getting people to exercise is really, really difficult, but getting people out of their chair might not be as difficult. Looking at the traditional exercise model or lack of exercise model, you can define behavior in terms of moderate and vigorous physical activity or exercise, and then everything else. And when you look at that, the more you exercise, the better your outcomes are, and you can fill in the blank here for diabetes risk, for depression, all sorts of things that are associated with exercise. But we spend 96% of our time in that sedentary to light category. So when you look at the balance between sedentary activity and light physical activity or sitting on your duff and puttering around as I like to think of it, you're actually pulling yourself in the direction of health or in the direction of disease. And so it really has become its own risk factor. It's not physical inactivity, it's sedentary behavior. So one of my specialties is measurement, and the objective measurement of sedentary behavior can be done with accelerometers, as I mentioned. There's two accelerometers I want to point out in particular. The first is the active pal, and the second is the actograph. The actograph has been widely used in physical activity type research, and the active pal is newer, but I want to bring it up because it's a triaxial accelerometer. It's actually worn on the thigh and attached with stickers. And that's important for the measurement that it does. It does 24-hour measurement, but it can measure posture. So it can tell you when you're sitting and when you're standing, and all other motion sensors that are not worn on the thigh don't have that advantage. And so most of the research you'll see in sedentary behavior with the actograph accelerometer, but I think you'll see more of the active pal in days to come. So if you look at accelerometers and our definition of sedentary behavior, you should really know what you're measuring. And accelerometers don't measure energy expenditure, they measure motion. So you're estimating low levels of energy expenditure with low levels of motion. And with the actograph in particular, you have no idea whether someone is sitting or just standing quietly. So with accelerometers, we're measuring motion. So that's one of the challenges of measuring sedentary behavior. Here's some of the promise of accelerometry for measuring sedentary behavior. If you look at the top of this graph, there it is. Person A is sort of your typical go-to-work, sit at your desk, exercise after work, and then watch TV in the evening. So their profile looks pretty good because they're meeting physical activity guidelines by getting a moderate to vigorous bout of physical activity. But if you look at Person B, this person spends the entirety of their day in light physical activity and sedentary behavior. And you can see they're only sedentary for three and a half hours, whereas this person is sedentary for nine hours a day. If you did an energy expenditure calculation on these two participants, Participant B is actually spending more energy than Participant A. So while you might think Participant A is healthier because they're exercising, that might not be the case. So sedentary behavior research is really important. In the future, we'll have better measures of sedentary behavior. And I say that because this is our project. Our colleagues at MIT have developed a system. It's two accelerometers, one worn on the wrist, one worn on the ankle. The accelerometers automatically stream the motion data to the mobile phone. The mobile phone uses the data network to stream the data to our secure server. And we have real-time measurement of both physical activity and sedentary behavior. Beyond that, it's a 24-hour system, so we have information about sleep as well. So there's a lot of potential for this as a measurement system. There's also a lot of potential for this as a feedback mechanism. So if you want to intervene on sedentary behavior, you can do it at the moment that you need to through the mobile phone. And here's a shameless plug for our study. If anybody wants to be a participant, we'll be recruiting in a couple of weeks. So let me get down to some results with sedentary behavior. One day of sitting reduced insulin activity in healthy adults. This effect was much worse than people who had consumed more calories than they needed. So it's a worse energy surplus. One hour of increased TV viewing time increased the risk of metabolic syndrome by 26% in women. And it looks like there might be a different effect in men and women with sedentary behavior. There's altered lipoprotein lipase activity or lipid metabolism with the longer you sit. And some really interesting research by Genevieve Healy points out that if you take two people with equal amounts of sedentary time, but one of them is kind of a fidgeter and gets up more often, they have better outcomes in terms of waist circumference, BMI, two-hour fasting glucose, and triglycerides. So that specific metabolism that might be happening when you sit down might be worse the longer you sit there. And there's a dose-response relationship between sitting and mortality from all causes. And this leads us to the question is, what is the link between sedentary behavior and these bad outcomes? Is it due to the decreased energy expenditure of sitting around? Or is it due to this metabolic deficiencies? And just to look at it in terms of an intervention with energy expenditure, if you take an 80-kilogram person and you decide that a good intervention would be to get them out of their chair for two hours a day. So you're going from one met to 1.5 met sitting to standing for two hours a day. That works out to 80 extra calories. If you were going to get that same intervention through exercise, this is a very moderate walk. You're going from one to 3.5 metts. You would need to walk for about 24 minutes to get the same energy expenditure from standing for two hours. And so actually, if you're looking at this energy expenditure, it might be a real challenge to get people out of their chair long enough to make it meaningful. But if you did a combination of exercise and decreased sedentary behavior, it might be a lot easier to get a meaningful difference in energy expenditure. So my assumption that the link between sedentary behavior and health outcomes was you sit a lot and you have a decreased caloric expenditure. And that's going to lead for this group, specifically to obesity. But there was some research done in 2008 that shows that the link is the other way. Obesity people were more likely to be sedentary at a later time point. Sedentary people were not more likely to be obese at a later time point. So there could be an interesting relationship between the metabolism of sedentary behavior and obesity. It could be that it's confounding on itself. So I'd like to challenge you as obesity researchers, I'm the physical activity researcher, to think about it as a 24-hour activity cycle. For any health outcome, say healthy weight, we want to think of activity in terms of adequate sleep and luckily with accelerometers we can measure all four of these things. Meeting physical activity guidelines, guidelines, so not forgetting about the exercise but including it in our model here. Encouraging light activity and then finally discouraging any sedentary activity. And I think that will lead to better outcomes. So in conclusion, the message is, get off your duff. And as obesity researchers, if we're successful, we can do smaller duffs. The preceding program is copyrighted by the Board of Trustees of the Leland Stanford Junior University. Please visit us at med.stanford.edu.