Middle East Health speaks to Dr. Robert Ojiambo, Ph.D., Associate Professor of Physiology and Biophysics, Weill Cornell Medicine-Qatar about the health risks associated with a sedentary lifestyle.
Can you describe sedentary behavior and elaborate on why it is considered an independent predictor of adverse health outcomes?
Sedentary behavior is any waking behavior spent in a sitting position or supine. Scientifically, it is defined as energy expenditure that is less than 1.5 metabolic equivalent tasks (METS). This results in the conservation of metabolic energy, which can then be used to fuel pathophysiological processes. There is existing evidence that if you spend time in sedentary behavior, you are conserving energy, and this conserved energy has negative health implications.
What are the primary cardiovascular risks associated with prolonged sitting?
Engaging in 150 minutes of moderate to vigorous physical activity (MVPA) per week protects against adverse cardiovascular (CVD) outcomes such as atrial fibrillation, myocardial infarction, heart failure, and cardiovascular mortality. A large study of 17,000 Canadian adults followed over 12 years showed a significant dose-response relationship between sitting time and cardiovascular mortality. In addition, an Australian study of 8,800 people found that individuals spending over four hours a day in screen-based activity, for instance, watching television, experienced up to 80% increased risk of cardiovascular mortality. A more recent study based on the UK Biobank examined a large sample of about 89,000 individuals over 8 years. It showed that even for individuals who meet the physical activity guidelines, engaging in more than 10 hours of sedentary behavior per day was associated with an increased risk of heart failure and cardiovascular mortality. That means even those who met the recommended physical activity guidelines were still exposed to some level of cardiovascular risk.
How does energy allocation to metabolic processes during sedentary behavior contribute to harmful health signals?
Current evidence supports the theory that human energy expenditure is constrained. All humans have an upper limit of sustainable energy expenditure levels. Total energy expenditure comprises basal energy expenditure (energy spent to maintain physiological processes) and activity energy expenditure (energy spent to support physical activity). It is worth noting that sedentary and active individuals tend to have similar total energy expenditure values.
Given that total energy expenditure is constrained (has an upper limit), it follows that for highly active individuals, energy will have to be reallocated from basal energy expenditure to support the high demands of physical activity. On the other hand, sedentary individuals have higher basal energy expenditure (reallocated from the unspent physical activity energy expenditure). Put differently, sedentary individuals have higher Basal Metabolic Rates (BMR) than active individuals. This high BMR is harmful because it is associated with cardiovascular disorders such as Type II Diabetes and correlates with increased visceral adiposity, chronic inflammation, and higher levels of circulating stress hormones – cortisol, adrenaline, and other dysregulated metabolic processes that are detrimental to health, resulting in poor cardiovascular outcomes. There is a clear pathophysiological connection in that when you have excess basal energy (higher BMR), it supports chronic inflammation and increased hormonal production, which are signals of dysregulation linked to cardiovascular disorders.
How do accelerometers help measure sedentary time accurately, and what limitations do they have?
Accurate measurement of sedentary behavior is problematic. Self-reporting tends to underestimate the time spent sedentary. Modern accelerometers with posture and heart rate detection features can accurately measure sedentary behavior since they generate counts when one moves. However, these devices are expensive for use in large-scale epidemiological studies. On the other hand, wearable technologies, such as smartwatch Apps, can be used to track personal sedentary behavior. Given the threshold for sedentary time of 10 hours per day, these devices can be customized to sound an alarm when approaching this threshold, thus acting as an effective population intervention strategy to reduce sedentary time.
With prolonged occupational sitting being unavoidable in many modern workplaces, how can workplaces reduce health effects?
There is already some evidence that reducing sedentary time by just 30 minutes and reallocating this time to moderate to vigorous physical activity can have health benefits.
Providing active workstations such as standing desks to promote working in an upstanding position can help minimize sitting. In addition, a cultural shift to allow standing during formal meetings, intelligent office designs with walking pads, intermittent exercise snacks (less than one-minute bouts of exercise to interrupt prolonged sitting), and office gyms allow one to be physically active in the workplace and minimize toxic sitting. Moreover, offices can encourage physical activity by placing office equipment at a distance from the desk, for instance, a printer where one must stand up and walk to the printer.
In Qatar, strategies are in place to encourage people to move more, such as large, airconditioned shopping malls, pedestrian walkways, parks, and souqs that provide opportunities to move and intuitively encourage ambulatory behavior.
There are also several innovative community initiatives to promote physical activity and healthy behavior at Weill Cornell Medicine-Qatar (WCM-Q) that fall under the Division of Continuing Professional Development (CPD), the Institute for Population Health (IPH), and Sahtak Awalan – Your Health First, WCM-Q’s flagship public health campaign. In addition, the intelligent building design at WCM-Q encourages movement across offices, lecture halls, labs, classrooms, and theatres.
How does urban living worsen sedentary behavior, and what is the cumulative impact of a sedentary lifestyle across work, commute, and leisure activities?
The conveniences of modern living promote sedentary lifestyles – screen-based entertainment, passive commute, and extensive use of labor-saving devices cumulatively spare energy. Deliberate effort is required to spend energy, and any opportunity at work or home should be used. There is a difference between physical activity and exercise. Exercise is planned and structured, like going to the gym. On the other hand, physical activity is spontaneous and natural. Running on a treadmill for 30 minutes is unnatural; walking to the mall to buy groceries is natural and doesn’t feel like work. The built environment design in urban areas has an impact on the population’s physical activity levels, and therefore, ecological designs should promote physical activity and minimize sedentary behavior.
Are there any ongoing studies or promising developments in this field?
Current studies in global cohorts are examining the energy demands of modern living and will shed light on energy balance and health. Currently, I am involved in a multinational initiative by the International Atomic Energy Agency (Total Energy Expenditure Across the Lifecourse), where we are looking at the energy demands of modern living and studying energy expenditures in China, Africa, Brazil, and other countries. Since the world is facing the obesity epidemic, we need to understand whether it is because of an inactive lifestyle or changes in diet.
There is existing evidence that if you spend time in sedentary behavior, you are conserving energy, and this conserved energy has negative health implications.
Additionally, mechanistic studies, such as those examining visceral adiposity, altered mitochondrial function, chronic inflammation, and dysregulated metabolic pathways, are recommended to investigate the relation between sedentary behavior/physical inactivity and CVD pathophysiology.
Studies to quantify thresholds for sedentary time with other clinical endpoints, CVD (ischemic heart disease), and all-cause mortality are also needed in the MENA region, as most evidence is in Western populations.
Learn more about combating obesity
To learn more about the clinical application of the concepts discussed in this interview, healthcare professionals can attend the ‘Tackling Obesity: Multidisciplinary Approaches for Comprehensive Care’ symposium. Hosted by the Division of Continuing Professional Development (CPD) at WCM-Q, the seminar will take place on January 25, 2025. Scan the QR code to register.
About Dr. Robert Ojiambo
Dr. Robert Ojiambo joined Weill Cornell Medicine-Qatar (WCM-Q) in July 2024 and currently holds the position of associate professor of physiology and biophysics. His research focuses on human energy balance and the relationship between energy intake, energy expenditure, and health.
Previously, Dr. Ojiambo served as the founding head of the physiology department and the chair of the division of basic medical sciences at the University of Global Health Equity in Rwanda.
Dr. Ojiambo has been actively involved with organizations in this field in Kenya, UK, China, and Austria. His work has been supported by funding from various organizations, including the Chinese Academy of Sciences, Catholic Relief Services, the Harvard University Center for African Studies, the Havey Institute for Global Health, and the International Atomic Energy Agency.
