Since the original study by Morris in 19531 showing that bus conductors in London experienced less coronary heart disease and mortality than bus drivers who would be sitting most of the time, there has been a large body of evidence proving the health benefits of physical activity.2 Numerous studies have shown that physical activity reduces total mortality, cardiovascular events, type 2 diabetes, obesity, and several types of cancer. Over time, most of the research in the field focused on the health benefits of moderate to vigorous physical activity and, specifically, on the role of aerobic exercise in preventing cardiovascular events and death. All this has resulted in guidelines from federal agencies and scientific organizations recommending frequent moderate to vigorous physical activity.3 More recently, research studies have tested the role of sedentary behaviour, the counterpart of physical activity, as a major cardiovascular risk factor. Sedentary behaviour includes activities that require <1.5 METs (metabolic equivalents) of physical effort such as sitting, using a computer, watching television, driving, etc. Epidemiological studies have demonstrated that sedentary behaviour, particularly prolonged sitting, increases total and cardiovascular mortality even in individuals who meet the recommended goals of weekly physical activity.4,5 More recent studies, assessing the association between sedentary lifestyle and health, highlight the possible role of standing (vs. sitting) to prevent obesity and metabolic dysregulation.6
Research studies showing the harmful effects of sedentary behaviour beyond regular physical activity and exercise have carefully followed statistical procedures to reach those conclusions. However, the message regarding the importance of decreasing sedentary lifestyle, even for people who perform regular exercise, may be confusing at first, as those two behaviours may be wrongly considered as mutually exclusive. People can be physically active performing hours of vigorous physical activity every week and still spend many hours in sedentary mode. Other people might be moving all day long without performing any formal or structured exercise. Adding more confusion to this is the message highlighting the importance of standing vs. sitting, as standing is not seen as a form of physical activity.
The study by Healy et al.7 published in this issue provides an important addition to the wealth of scientific evidence highlighting the importance of avoiding sedentary behaviour. Using clever statistical methods of isotemporal substitution analysis, the authors were able to account for the complex relationship between sedentary lifestyle, physical activity and exercise, stepping, and standing time. This study, different from most studies assessing sedentary behaviour and health outcomes, measured sitting time objectively and did not rely on surveys to measure activity, providing a unique opportunity to assess accurately the potential metabolic benefit of standing vs. sitting. This study demonstrated that replacing sitting by standing improves fasting plasma glucose, triglycerides, and atherogenic cholesterol ratios. This study also demonstrated that stepping was strongly associated with a lower body mass index and waist circumference and also improved plasma glucose, triglycerides, and atherogenic lipids. More importantly, replacing standing by stepping resulted in better weight control but not necessarily in better atherogenic cholesterol ratios.
The results of this study have major public health implications and add to results of previous studies assessing the importance of avoiding sitting time and adding physical activity, even at levels of intensity that will not qualify for weekly goals of activity. With the growing epidemic of obesity, diabetes, and cardiovascular disease in the world, there is an urgent need for simple, pragmatic, and scalable recommendations to decrease sedentary behaviour in the population. It is very clear that the fight against sedentary behaviour cannot be won based only on the promotion of regular exercise. Relying on fitness centres to increase physical activity in the general population means that a city of 100 000 inhabitants would require at least 200 fitness centres to accommodate the needs of exercise for everybody. It is unrealistic to expect people in extreme climates to jog outdoors year-round or to expect most of the population to buy exercise equipment for home use. While pursuing exercise must continue as a recommendation for health promotion, it is clear that avoiding sedentary behaviour relies primarily on increasing non-exercise activity thermogenesis (NEAT) more than on achieving weekly goals of exercise.7 Indeed, the incorporation of NEAT in daily life may represent a major change in caloric expenditure, more significant than what regular exercise would do, as displayed in Figure 1. A person walking while at work for 2 h, standing for another 4 h, and performing some daily chores at home for another hour will burn more calories than jogging or running for 60 min. Thus, there is a need for more emphasis to increase NEAT in our daily lives than on achieving goals of vigorous exercise in order to decrease sedentary behaviour.
Total caloric expenditure in a 26-year-old man in different scenarios of physical activity/inactivity. The caloric expenditure enhancing non-exercise activity thermogenesis will lead to a higher caloric expense than performing 30–60 min of moderate to vigorous exercise.
The recommendations to decrease sedentary behaviour face significant challenges related to human nature and cultural factors. Naturally, humans will always try to use the shorter path and opt for activities that require the least amount of physical effort. To prove this, all we need to do is watch the car parks. People will generally park as close as they can to the destination, which is ironic in the car park of a fitness centre. In shopping centres and other buildings, you would see more people using the escalators than using the stairs, where many people use the escalator to go up or down only one or two floors. Cultural and environmental factors also affect our choices. We live in an environment that gives a higher value to things that promote sedentary behaviour and treats society as handicapped—automatic doors, escalators, petrol-powered lawn mowers, and even automatic dustbins whose lids open automatically. They represent socially desirable things promoting sedentary behaviour under the name of comfort and convenience. One of the most interesting paradoxes of the modern man is to pay extra money to buy a car with electric windows, power steering, and remote locking, and then drive to a fitness centre to push, pull, and lift heavy things. Conferences on health promotion and classes about the detrimental effects of sedentary behaviour occur when attendees are sitting for hours, equalling smoking cigars while attending a conference on the effects of tobacco. As a society, we have accepted ‘no physical effort’ as a desirable goal.
Sedentary behaviour and environments promoting it are also seen as a sign of progress and economic power. In low and middle income countries, measures of low socio-economic status include using a bicycle instead of a car and not having a maid to do household chores. In those countries, many activities of daily life requiring physical effort are generally performed by the poor, stigmatizing opportunities to avoid sedentary lifestyles. In every country, the bigger and more comfortable the chair, the more important is the job. Interestingly, in the English language, chair also means chief or director, making a piece of furniture a synonym of power and rank. Conversely, standing locations in football games across Europe are the cheapest, as are the tickets to watch the opera while standing, signalling that standing is for poorer people while sitting is for those who are better off. This pervasive culture that values sitting and other sedentary activities and depreciates physical effort requires a radical shift so changes to reduce sedentary behaviour can occur.
Fortunately, an ongoing revolution against sitting has already started. Countries such as Australia have campaigns promoting less sitting time as part of their public health initiatives.9 Some companies around the world are promoting the use of standing desks, reducing sitting time, and becoming creative to promote standing and stepping. It might sound very optimistic, but the time will probably come when classes in schools will include standing time, and office jobs will give employees the option to sit, stand, or walk on a treadmill while at work. People will eventually be able to attend a cinema or even conferences where everyone is using a treadmill, a small stepper, or a stationary bike while using headphones to listen. Stairs will become more visible and attractive in every building, while escalators and lifts to go up one floor or two will be reserved for the disabled. We might be required to pedal something in our office from time to time to maintain our computer screen on and will be holding walking meetings. Although some of those scenarios might seem like a scene from a science fiction movie, the reality is that our current pervasive sedentary-prone environment was also the result of intentional changes that happened over time to make our life better. The unintended consequences of modern life promoting sedentary behaviour can be reversed. Healthcare providers, policy makers, and people in general need to stand up for this. Literally.
The study was supported by a research grant by the European Regional Development Fund, project FNUSA-ICRC. (Z.1.05/1.1.00/02.0123).