What Happens If We Sit for More Than 8 Hours Per Day?
Sitting for more than 8 hours per day increases the chances of becoming overweight or obese, unlike sitting for only 4 hours per day, according to a recent Latin American study published in BMC Public Health.
These data come from almost 8000 people aged 20 to 65 years (half of whom are women) who participated in the Latin American Study on Nutrition and Health (ELANS). The cross-sectional survey included representative samples from urban populations in Argentina, Brazil, Chile, Colombia, Costa Rica, Ecuador, Peru, and Venezuela. The average time spent sitting was 420 min/d. Ecuador had the lowest time (300 min/d), and Argentina and Peru had the highest (480 min/d).
No amount of sitting time has been associated with a greater health risk, but the World Health Organization recommends that sitting time be minimal.
“We used to believe that any intense physical exercise could compensate for a sedentary life. But now we know that a sedentary lifestyle in general and sitting time in particular have a direct effect and are an independent risk factor for chronic diseases,” said study author Irina Kovalskys, PhD, a pediatric specialist in nutrition and a professor of nutrition at the Catholic University of Argentina and a principal investigator of ELANS.
Kovalskys stated that the 420-min average sitting time is worrying in a population such as the one studied, in which 60% of adults are obese and there are high rates of cardiometabolic risk factors. She affirmed that it is important to raise awareness among the population and focus on adolescents.
Felipe Lobelo, PhD, is a Colombian physician, an associate professor of global health at the Rollins School of Public Health at Emory University, and director of epidemiology at Kaiser Permanente Georgia, in Atlanta, Georgia. He did not participate in this study but promotes the concept of exercise in medicine. The activity of the patient must be included in a clinical setting, and improving the level of physical activity can have a positive impact on health prognosis, he said.
“To make public health recommendations or even advise patients, a cutoff point is needed. Guidelines recommend 150 minutes per week of moderate to vigorous physical activity, and some countries have started to indicate that we should be concerned about people’s sitting time. There is still no equivalent to the 150 minutes, therefore, these studies are important, especially in the Latin American population,” said Lobelo.
He explained that the concept of an increased risk of death or chronic disease due to lack of physical activity arose in the past 50 years, but only in the past two decades have we started thinking about sitting time.
“Spending more than 8 hours sitting per day clearly causes a much higher risk of chronic diseases, including obesity and diabetes. It may be a continuous and progressive association, and the point at which this increase becomes exponential is clearly between 6 and 8 hours of sitting time,” Lobelo added.
The authors expected to find a linear association with risk for being overweight or obese after 4 hours, but they did not find one. “This study has limitations. Among them was that other indicators were not considered, such as health indicators. Collaborations are starting with other research groups, and other studies are being designed,” said study author Gerson Ferrari, PhD, an associate professor at the School of Sciences in Physical Activity, Sports, and Health at the Medical Sciences Faculty of the Santiago de Chile University.
The Latin American study tried to establish a sitting cutoff time after which the risk of becoming overweight or obese increases. It used three indicators of excess weight: body mass index (BMI), waist circumference, and neck circumference.
Sitting for more than 8 hours increased the chances of excess weight by 10% when measured by BMI and by 13% when neck circumference was used.
Ferrari stated that the result obtained measuring BMI is the one that should be considered, because it is used in public policy. Neck circumference is a more recent measurement of detection and it is less studied, but it is a valid indicator, with good sensitivity and advantages over others, such as ease of measurement and lack of variation over time.
According to the results of this study, measuring neck circumference may be the most sensitive method of the three. Neck circumference was proportionally greater in people who sat for ≥4, ≥6, and ≥8 h/d than in those who sat for < 4, < 6, and < 8 h/d. This relationship was not observed with the other indicators.
Broaching the Topic
“What is important is uninterrupted sitting time. The recommendation is to break up those sitting times with active periods. Health professionals have already incorporated the concept of moderate to vigorous physical exercise, but nonintense activities are sufficient to reduce sitting time. Yoga may not be vigorous, but it is valuable at reducing sitting time,” said Kovalskys.
Ferrari recommended giving patients concrete messages so that they spend as little time possible sitting. “It is better to stand on the bus or the subway even when there is a place to sit. Are you going to talk on the phone? It is better to do it while walking or at least standing instead of sitting.”
A recent literature review conducted by investigators of the University of Birmingham in the United Kingdom studied the possible molecular and physiologic mechanisms of inactivity time, health consequences, and protection strategies. It offers an evaluation of interventions that can compensate for the immediate negative consequences of inactivity.
Some studies suggest that more than 60 min/d of moderate-intensity exercise or more than 150 min/wk of moderate-intensity to vigorous exercise may be effective at mitigating the increased risk for mortality associated with sitting time, but reduced intensity may not be enough.
Interrupting sitting every 30 to 60 min to walk or cycle (2 to 10 min), performing 3 minutes of simple resistance activities every 30 minutes, such as calf or knee lifts, performing intermittent leg movements (1 minute of activity for every 4 minutes of inactivity during a 3-hour protocol session), or pausing to climb stairs (5 minutes every hour) may be beneficial for vascular health. However, not all studies have demonstrated these positive effects, therefore, some populations may need exercise of greater intensity or duration to counteract the negative vascular effects of acute inactivity periods.
Standing workstations are effective at reducing sitting time in offices but may be ineffective at reducing vascular alterations related to sitting time. Although some experimental studies indicate vascular benefits, epidemiologic studies suggest that long periods of standing can be harmful to vascular health, especially for venous diseases. Recommendations for use should be accompanied by specific regimens on the frequency and duration of the position to attain the maximum benefits and minimize other vascular complications.
One problem that Lobelo noted is that some doctors ask their patients how active they are, but they do so in a nonstandardized manner. This observation led him to publish, together with the American Heart Association, an article on the importance for health systems of considering physical activity as a vital sign and including it in records in a standardized manner.
He said that “one advantage of having physical activity as a vital sign in patient medical records is that it allows us to identify individuals who are at greater risk.”
Kaiser Permanente asks the following questions: how many minutes of physical activity do you perform regularly per week, and what is the average intensity of that activity? Patients can be classified into the following three groups: those who follow the recommendations, those with almost no activity, and those who perform some physical activity but do not meet the recommended 150 min/wk of moderate to vigorous activity.
Recording sitting time is more difficult. Lobelo indicated that “it is easier for a person to remember how much time they spent running than how long they were sitting.” Regarding the use of technology, he commented that most watches provide a good estimate. Without technology, it can be estimated by asking how much time is spent in the car, on the bus, or in front of the computer or television and then adding up these times.
Lobelo emphasized that the two behaviors, lack of physical activity and excessive sitting time, have independent associations with health outcomes. But if both are combined, the risk of obesity, diabetes, and cardiovascular diseases is not just added but rather is multiplied. These behaviors contribute to the epidemic of obesity and diabetes, since most people do not follow either of the two recommendations.
“Studies show that of the two behaviors, the more negative for health would be not following the physical activity recommendations,” said Lobelo. “If the recommendation of 150 min/wk of moderate to vigorous physical activity is followed, the associated risk of sitting too much declines by 80% to 90%. Additionally, we can prevent, help to manage, and decrease the risk of complications in more than 100 diseases, including infections. During the pandemic, it was observed that more active people had a lower risk of dying or of being hospitalized due to COVID-19 than less active people, independently of other factors, such as hypertension, diabetes, and obesity.”
Moreover, Lobelo believes in “practicing what you preach” and advocates that doctors become healthy models.
Lobelo, Ferrari, and Kovalskys, have disclosed no relevant financial relationships.
Follow Roxana Tabakman of Medscape Spanish Edition on Twitter @RoxanaTabakman
This article was translated from the Medscape Spanish edition.
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