Breaking Up Prolonged Sitting Reduces Postprandial Glucose and Insulin Responses

These findings provide initial experimental confirmation of hypotheses generated by epidemiologic observational studies on the deleterious health consequences of prolonged sedentary time (too much sitting as distinct from too little exercise). Of particular importance is the potential for reducing cardiovascular disease risk by briefly breaking up prolonged periods of sitting with activity of at least light intensity. Brief interruptions to sitting led to significant reductions in postprandial glucose and insulin, irrespective of the activity intensity. The 24–30% lowering in the plasma glucose iAUC and the 23% lowering in the insulin iAUC seen after the activity break conditions, at the very least, is comparable in magnitude to an acute bout of moderate-intensity aerobic or resistance exercise in overweight/obese individuals (32).

Our findings are the first to document, among overweight/obese adults, an elevated postprandial glucose and insulin response during an acute bout of prolonged sitting, relative to sitting with brief activity interruptions. Among young nonobese adults, significant reductions in whole-body insulin sensitivity have been observed after 1 day of prolonged sitting (24). The magnitudes of changes observed in postprandial glucose and insulin during the uninterrupted sitting condition in our study are consistent (∼23–30%) with the changes in metabolic outcomes reported after 1 day of prolonged sitting (24). The lowering of postprandial glucose and insulin suggests both increased insulin sensitivity and reduced insulin secretion, the latter effect consistent with preservation of pancreatic β-cell function. Intervention study findings demonstrating that blunting of postprandial spikes in glucose improves inflammation and endothelial function (33) and reduces carotid intima-media thickness (11,33) suggest that the blunted glucose response seen in our study through the inclusion of three brief (2-min) activity breaks per hour during prolonged sitting may ameliorate such consequences of postprandial hyperglycemia (9,18).

Although larger reductions in postprandial glycemia have yielded clinical benefits to surrogate cardiovascular end points, including carotid intima-media thickness (8), smaller differentials in the postprandial glucose seen in response to pharmaceutical agents, generally comparable in magnitude to those seen in the activity break conditions, have been linked to reductions in oxidative stress, circulating adhesion molecules, and endothelial function in patients with and without type 2 diabetes (6,8,33). Additional research using measures of inflammation and endothelial function will be necessary to further elucidate the influence of frequent breaks from sitting and whether the exaggerated postprandial glucose response observed after 5 h of uninterrupted sitting is more pronounced when imposed over multiple days. Potential long-term consequences, both beneficial and deleterious, of different sitting-time patterns are needed to strengthen the case for relevant public health and clinical initiatives.

These findings support the hypothesis that brief interruptions to sedentary time with a minimum of light-intensity physical activity can attenuate acute postprandial plasma glucose and serum insulin response during prolonged sitting. Importantly, the brevity of the interruptions to sitting (2 min) indicates that such breaks would not count toward the minimum amount of aerobic activity necessary for substantial health benefits within current physical activity guidelines because at least 10-min episodes of activity are stipulated (34). However, consistent with studies of the effects of continuous exercise on glucose metabolism (35), the sum of total activity time over a 5-h period was 28 min. A logical next step would be to build on these findings to design a study that would provide a head-to-head comparison of a single continuous exercise bout to the breaking up of prolonged sitting protocol used in this study.

The moderate-intensity activity break condition was relatively strenuous for some of our study participants. Our original protocol called for a consistent 6.4 km/h for all participants, but we found it necessary to slightly reduce the speed for some so that they could complete the prescribed 2-min moderate-intensity bouts without discomfort. Thus, the higher-intensity breaks condition was close to the practical maximal feasible intensity for these overweight/obese individuals and likely close to the tolerable upper limit of activity for expected physiologic benefit.

Our trial does have some potential limitations. First, it examined acute effects of a 1-day exposure to prolonged uninterrupted versus interrupted sitting; thus, implications cannot be extrapolated to long-term exposures. Second, it examined activity bouts of fixed frequency and length. Systematic variations in length and frequency of activity bouts and possible moderating effects of factors such as sex and adiposity status should be examined.

Our experimental protocol involved brief and regular interruptions (2 min of activity for every 20 min sitting) to prolonged sitting time. Interrupting sedentary time in this way could be feasible in domestic and workplace settings where adults sit for prolonged periods (36). However, further experimental evidence that can define dose-response relationships is required. For example, evidence from animal studies (37) suggests that it may be important primarily to interrupt the contractile inactivity in postural muscles that takes place during prolonged sitting. From body weight–dependent equations (38), it is estimated that treadmill walking at 3.2 km/h in people weighing 90.5 kg demands an energy expenditure of only 18.8 kJ/min, yet most forms of nonexercise activity that naturally interrupt sitting would be expected to yield even less energy expenditure. Although the body weight–dependent equations do not cover the 5.6–6.4 km/h walking speed used in this trial, it would be realistic to expect that the energy expenditure for the moderate walking bouts would be expected to exceed the 25.6 kJ/min estimated for walking at 4.8 km/h. Simply regularly standing up for a short period may have beneficial metabolic effects. Estimating the caloric expenditure of such changes would be informative; the increased substrate utilization that is required to meet differences in energy demands when transitioning from sitting to standing may be an important mechanism (37,38). However, whether simple brief standing, as opposed to longer activity bouts, will be protective for metabolic health, remains to be determined.

Given the high prevalence of overweight and obesity among those of low socioeconomic status living in affluent populations (39) and the average “greying” of demographic profiles, our study participants are representative of large numbers at risk for developing type 2 diabetes and subsequent cardiovascular complications. Pragmatic trials with large numbers of participants would be highly informative (40), such as demonstrating metabolic health effects of reducing and breaking up sitting time in the workplace over sustained periods of time (i.e., months or years) among representative groups of working adults.

Read the full study

Sedentary Behavior and Prevalent Diabetes in 6,166 Older Women: The Objective Physical Activity and Cardiovascular Health Study

Background

We examined associations of sedentary time and sedentary accumulation patterns (ie, how sedentary time is accumulated) with prevalent diabetes in an ethnically diverse cohort of older women.

Methods

Community-dwelling women aged 63–99 (n = 6,116; median age = 79) wore ActiGraph GT3X+ accelerometers 24 h/day for up to 7 days from which we derived average daily sedentary time and three measures of sedentary accumulation patterns: breaks in sedentary time, usual sedentary bout duration, and alpha. Odds ratios (ORs) and 95% confidence intervals (CIs) for prevalent diabetes were estimated using multivariable logistic regression.

Results

Twenty-one percent (n = 1,282) of participants had diabetes. Women in the highest quartile of sedentary time (≥10.3 h/day) had higher odds of diabetes (OR = 2.18; 95% CI = 1.77–2.70) than women in the lowest quartile (≤8.3 h/day). Prolonged accumulation patterns (ie, accumulating sedentary time in longer sedentary bouts) was associated with higher odds of diabetes than regularly interrupted patterns (comparing quartiles with the most vs least prolonged patterns: usual bout duration OR = 1.57, 95% CI = 1.28–1.92; alpha OR = 1.61, 95% CI = 1.32–1.97); however, there was no significant association for breaks in sedentary time (OR = 1.00, 95% CI = 0.82–1.20).

Conclusions

High levels of sedentary time and accumulating it in prolonged patterns were associated with increased odds of diabetes among older women.

Original full study

Sitting kills

When you sit for long periods without getting up, the large weight-bearing muscles of the legs remain dormant. 

With no action, these muscles are unable to efficiently use the sugars and fats that float around in your blood - and in theory, this could lead to weight gain and metabolic diseases such as diabetes.

At the same time, reduced blood flow in your arteries leads to hostile conditions that promote injury to the blood vessel walls. 

Over a lifetime, this injury likely contributes to heart disease and to peripheral artery disease. 

Furthermore, when your leg muscles remain shut off for long periods, blood collects in your veins which leads to an increased risk for blood clots, or deep venous thrombosis. Standing up and moving around can stop these processes, but all too often, we just keep sitting.

Sitting patterns

Sitting patterns describe how people sit throughout the day. 

Some people commonly sit for long periods at a time, rarely getting up. They are said to have prolonged sitting patterns.

Others rarely sit still.They regularly get up after sitting for just short periods. 

These sitters are said to have interrupted sitting patterns. Where do you fit on the sitting pattern spectrum?

Are sitting patterns important for metabolic health? 

Emerging evidence suggests yes. From observational studies, we learned that adults with prolonged sitting patterns had larger waistlines, higher BMI, and in their blood had less good fats, more bad fats, and higher levels of sugar compared to adults with interrupted sitting patterns.

To test whether problems with fat and sugar metabolism were being caused by sitting patterns, researchers around the world conducted experiments. 

They brought adults into a laboratory at least two times each, having them sit continuously for about eight hours (an extreme prolonged pattern. 

On the second day, the participants were asked to get up every 20-30 minutes (a highly interrupted pattern). The interruptions lasted for two to five minutes and included standing still, light walking, simple resistance exercises or moderate-intensity walking, depending on the study.

When researchers synthesized evidence from most of the laboratory studies, the results were clear. 

On days with prolonged patterns, our bodies are not able to metabolize fats or sugar as well as they are on days with interrupted patterns. 

Blood pressure and fatigue were also higher on days with prolonged sitting compared to days with interrupted patterns.

These groundbreaking laboratory studies provided strong evidence that sitting patterns had an immediate effect on how the body processes fats and sugar, otherwise known as metabolism. 

This led to the idea that prolonged sitting patterns over a lifetime could contribute to metabolic diseases such as diabetes in later life. 

Since diabetes can take a long time to develop, this question cannot be feasibly tested in a laboratory. Instead, we turned to an observational study of the population to help answer the question.

Are sitting patterns related to diabetes?

We recruited over 6,000 women aged 65-99 from the Women’s Health Initiative and measured their sedentary patterns for seven days using research-grade activity monitors. We also had over 20 years of detailed health records, which included information on whether the women had ever been diagnosed by a physician with diabetes.

As expected, the group with the most prolonged sedentary patterns had the most women with diabetes. The group with the most interrupted patterns had the fewest women with diabetes.

We used advanced statistical procedures to account for differences in other factors such as dietary habits, physical activity, medication use, weight, age, alcohol and cigarette use, and overall health, giving us more confidence that the sitting patterns were in fact driving the findings. 

We should caution, however, that since we did not measure sitting patterns before the women were first diagnosed with diabetes, we do not know whether the sitting patterns contributed to diabetes or whether the diabetes changed their sitting patterns. 

We ran additional statistical tests to try to untangle that, which indicated that sitting patterns contributed to diabetes. However, additional studies specifically suited to answer the question of causation are needed.

While this was the first study of sedentary patterns and diabetes exclusively in older adults, our results were remarkably similar to recent findings in a younger cohort. 

Researchers from the Netherlands studied 2,500 adults ages 40-75 and found that prolonged sitting patterns were associated with Type 2 diabetes and with metabolic syndrome.

Conclusions and words of advice 

Based on the findings from our study and those of the Dutch researchers, when viewed with the earlier epidemiologic data and findings from the laboratory experiments, it seems that sitting patterns may contribute to the growing international diabetes epidemic.

With that said, as with all science, these first few studies are only the beginning of the story. Much more work lies ahead. 

For the time being, there is a possibility that changing your sitting patterns might provide protection against diabetes, especially if long sitting bouts were always broken with light activity or even better, moderate-intensity activity, as recommended by the American Diabetes Association.

Read the original article with links

Health risk

• Research shows that the more time you spend sitting, the shorter and less healthy your life will tend to be, even if you exercise regularly, thanks to the negative impacts on your cardiovascular and metabolic function
• When you sit, lack of muscle contraction decreases blood flow through your body, reducing the efficiency of biological processes
• For every hour you sit, your life expectancy decreases by two hours. Research has also found that sitting for more than three hours a day causes 3.8 percent of all-cause deaths
• Twenty to 25 minutes of walking per day may add anywhere from three to seven years to your life span. As little as two hours of walking per week may also reduce mortality risk in older adults. Brisk walking has even been shown to improve life expectancy in smokers and overweight individuals
• For optimal health, aim to sit less than three hours a day, walk 10,000 to 15,000 steps per day, incorporate the Nitric Oxide Dump exercise into your daily routine. Then, when ready, add a comprehensive workout plan
• 
  

The elderly and those struggling with chronic disease that prevents them from engaging in more strenuous fitness regimens would also do well to consider walking more. While often underestimated, studies show you can reap significant health benefits from it. For example:

• Walking 2 miles a day or more can cut your chances of hospitalization from a severe episode of chronic obstructive pulmonary disease by about half16,17
• Walking has also been shown to reduce the risk of stroke in men over 60. Walking for one to two hours a day cut a man’s stroke risk by as much as one-third, and it didn’t matter how brisk the pace was. Taking a three-hour walk each day slashed the risk by two-thirds18
• Twenty to 25 minutes of walking per day may add anywhere from three to seven years to your life span19
• As little as two hours of walking per week may also reduce mortality risk in older adults, compared to inactivity. Meeting or exceeding the activity guidelines of 2.5 hours of moderate activity per week in the form of walking lowered all-cause mortality by 20 percent20
• Research published in 2012 found brisk walking improved life expectancy even in those who are overweight.21 Smokers may also increase their life span by nearly four years by taking regular walks22

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Sitting is killing you but....

In short, if you are standing all day:

• You are going to burn more calories.
• You will most likely increase your HDL cholesterol (aka the ‘good’ cholesterol).
• You may lose a little weight.
• You’ll probably be in a better mood.
• And even cooler, standing has an anti-aging benefit.

And while there isn’t a ton of scientific research to back this up, I will argue that you are more creatively engaged with your project and can maintain focus for longer periods of time. As Walter Murch said in our podcast together, being a film editor (like many other highly creative professions) is a combination of being a surgeon, an orchestra conductor, and a short order cook…all of whom stand while working.  

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Sitting is killing us

Humans are not sedentary creatures, but modern televisions, computers, and automobiles have forced people to spend far longer sitting down than standing up. This has serious consequences for the weight of individuals, the posture of many people, and ultimately the lifespan. This infographic explains the candid truth about the amount of time we all spend sitting on a daily basis.

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Sitting

"Women who lead a sedentary lifestyle have faster-ageing cells than those who exercise every day," BBC News reports.

This research looked at telomeres – often likened to the caps at the end of shoelaces, they are made up of molecules that protect strands of chromosomes from "fraying".

Telomeres shorten every time the genetic information in cells is duplicated. It's believed that this leads to cell ageing and death.

In a sample of older women, the researchers looked at whether there was an association between time spent sitting down and telomere length.

Telomeres are measured in the small sections of nucleic acids that make up DNA, known as base pairs. 

Among women in the study who did less than about 40 minutes of physical activity a day, those who sat longest had shorter telomeres by an average 170 base pairs.

The researchers say telomeres shorten at a rate of 21 base pairs a year – using a rough "back of a fag packet" calculation, 170 equals about eight years.

Sitting time did not seem linked to telomere length for women who did at least 30 minutes of physical activity a day.

We don't know whether the results apply to men or younger people.

And, importantly, as the study only looked at the women's activity levels and telomeres at one point in time, we don't know whether activity levels or sitting causes telomeres to shorten.

Still, arguably, most of us would benefit from spending less time sitting down.

Where did the story come from?

The study was carried out by researchers from the University of California, San Diego State University, the State University of New York at Buffalo, the University of Washington, the Fred Hutchinson Cancer Research Centre, George Washington University, the University of Florida and Northwestern University, all in the US.

It was funded by the US National Heart, Lung and Blood Institute. 

The study was published in the peer-reviewed American Journal of Epidemiology on an open access basis, so it's free to read online.

All of the UK media outlets that covered the study implied that a direct cause and effect relationship between sitting down and cell ageing had been proven.

For example, the Mail's headline stated that, "Women who spend at least 10 hours on their backsides each day speed up their aging process."

This is untrue. While there certainly seems to be an association worthy of further research, no causal link has been established.

What kind of research was this?

This cross-sectional study used data from women taking part in a much bigger study of health called the Women's Health Initiative.

Cross-sectional studies can find correlations between different factors – in this case, sitting time and telomere length.

But because this type of study only looks at one point in time, researchers can't say which factor happened first, so it's not very useful for telling us whether one causes the other.

What did the research involve?

Researchers used information about 1,481 women aged over 65 who'd taken part in various sub-studies of the Women's Health Initiative.

They used information from women who'd had their physical activity measured using accelerometers (devices that measure movement) and had also given DNA samples that had been tested for telomere length.

After accounting for other factors, they looked at whether telomere length was linked to the amount of time spent sitting.

The information about physical activity was measured over one week, during which time women wore their accelerometer all the time, except when bathing or swimming.

Women taking part also completed a questionnaire about their physical activity and kept a record of their sleep. Telomere length was measured from DNA in blood cells.

The researchers took account of the following possible confounding factors:

• age and ethnic background
• education level
• marital status
• smoking and alcohol consumption
• body mass index
• hours of moderate to vigorous physical activity each day
• long-term diseases
• use of hormone medicines

They also redid their calculations to divide the women into those who did more or less than the average amount of physical activity (about 40 minutes).

They then looked at the link between time spent sitting and telomere length for women who did more or less than 40 minutes physical activity a day.

They also looked at the link between sitting and telomere length for women who did 30 minutes or more a day, the recommended activity level for all adults.

It's unclear whether these additional calculations were planned from the start of the study, or whether the researchers decided to do them because the initial findings did not show a link between time spent sitting and telomere length.

What were the basic results?

The length of time spent sitting was not linked to telomere length for women who did 30 minutes or more of moderate physical exercise a day.

For women who did less than the average amount of moderate physical activity each day, time spent sitting did show a link to telomere length.

Among these women, those who spent more than about 10 hours a day sitting had shorter telomeres than those who spent less than about eight hours a day sitting. The average difference was 170 base pairs (95% confidence interval [CI] 4 to 340).

Women who spent the most time sitting were more likely to be older, white, obese and have long-term illnesses.

How did the researchers interpret the results?

The researchers said their results suggest that, "Prolonged sedentary time and limited engagement in moderate to vigorous physical activity may act synergistically to shorten leukocyte telomere length among older women."

In other words, being both sedentary for long periods and not getting much physical activity may act together to shorten telomeres in blood cells.

They speculated that causes of the link might include insulin resistance, lack of the anti-inflammatory responses the body has to exercise, or obesity.

They also acknowledged women who have long-term illnesses are more likely to have a sedentary lifestyle, and the illness rather than the lack of exercise may cause shortened telomeres.

Conclusion

It's not news to anyone that being more physically active and spending less time sitting around is likely to keep people in better health.

But this study has many limitations that make it difficult for us to rely on its results.

While they are used as a marker for ageing cells, telomeres are not a direct measure of ageing. Although shortened telomeres have been linked to certain diseases, everyone's telomeres shorten over time.

Saying shorter telomeres make someone "biologically older" doesn't mean much. This hasn't stopped the emergence of private companies offering to measure your telomeres – but it's unclear what exactly you could usefully do with that information. 

And the only cells studied in this research were blood cells, so we don't know whether the results would have held for brain cells, muscle cells or any other cells in the body.

Doctors have tried to disentangle the effects of physical activity from the effects of being sedentary before without much success.

Generally, as in this study, research seems to show that if you get plenty of moderate to vigorous physical exercise, the amount of time you spend sitting or lying down doesn't make much difference.

The researchers carried out a lot of comparisons and used multiple models to try to show sedentary time was linked to telomere length.

In most of these models, once you take account of women's age, ethnicity, body mass index and long-term illnesses, there was no link.

Only when the researchers stratified the results by how much physical activity women did could they show a link in one category: those who did the least physical activity.

That suggests sedentary behaviour is not the strongest factor to affect telomere length.

Another problem with the study is it only looked at telomere length and physical activity at one point in the women's lives.

We don't know how much physical activity they'd done throughout their lives, or whether their telomeres had shortened faster than other women recently or at an earlier stage in life.

The study doesn't add much to what we already know: physical activity is likely to be beneficial for people at all stages of life, and everyone should aim to get at least the recommended level of 30 minutes of moderate to vigorous physical activity a day.

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Sitting

"Middle-aged male office workers 'more sedentary than over-75-year-olds'," The Daily Telegraph reports.

A survey in Scotland suggests previous studies may have underestimated sedentary behaviour in middle-age by not asking about time at work, which for many people increasingly involves sitting at a desk.

Researchers surveyed more than 14,000 people about their time spent doing activities – including work – sitting down. They found that on weekdays, people who worked reported a longer amount of time sitting down compared to those aged 75 and above.

At the weekends, this was reversed, possibly suggesting that some office workers were trying to compensate for their sedentary working week.

Among all men – workers and non-workers – most age groups reported being inactive for longer than pensioners. The opposite was true for women: overall, women were found to be more active than pensioners.

The authors suggest the sedentary lifestyle created by the work environment is a public health risk for cardiovascular disease, diabetes and some cancers. This suggestion is backed by a large body of research discussed in our article "Why we should sit less".

Getting active at work might be easier than you think: you could cycle or walk for part or all of your journey, walk over to someone's desk rather than emailing or phoning, use your lunch break to exercise and use the stairs instead of getting the lift. Read more advice about How to boost your health at work.

Where did the story come from?

The study was carried out by researchers from the Physical Activity for Health Research Centre in Edinburgh. One researcher was funded by a PhD college award from the University of Edinburgh, while the other authors all held positions at the University of Edinburgh.

The study was published in the peer-reviewed Journal of Sports Sciences.

The UK media reporting of the story is broadly accurate, highlighting the main finding that middle-aged workers were more sedentary than pensioners on weekdays.

But The Sun failed to mention that the trend was reversed at the weekends and those in the middle-aged categories were in fact the most active at these times.

Also, the Telegraph reports that "Middle-aged male office workers spend more time sitting down than pensioners", which implies that it is a gender specific problem. While the difference was more pronounced in men, female workers also spent a longer average time being sedentary compared with those 75 and above.

What kind of research was this?

This was a cross-sectional survey of Scottish adults looking at sedentary behaviour including time spent sat down at work and how this varies across age groups and gender.

This kind of study is good in that it can recruit a large number of people, and thus give a fair representation of the country as a whole.

However, as they are only surveyed once with no follow-up, it is a snapshot picture and we cannot say if these trends have been consistent over time.

What did the research involve?

Adults (those aged 16 and over) in Scotland were asked to participate in the Scottish Health Questionnaire in 2012, 2013 or 2014 to find out the amount of sedentary time in each age category and in men and women. The Scottish Health Survey is an ongoing project designed to provide a detailed picture of the health of the Scottish public.

In total, 14,367 participants were asked to report on their time spent in sedentary activities from three areas:

• time spent sitting at work on a standard day
• leisure time spent sitting watching the TV or other screen devices on a typical weekday and weekend day
• time spent in other leisure sedentary activities such as eating a meal, listening to music or reading, on a typical weekday and weekend day

They assumed that a typical working day was on a weekday.

The participants were split into 10-year age bands starting from the age of 16 and split by gender for analysis.

What were the basic results?

On weekdays:

• For all adults in work, total reported sedentary time was higher for each age category than for those 75 and over.
• For men in work, the biggest difference was between those aged 55 to 64, who were on average sedentary for 84 minutes longer than those aged 75 and above per day; 7.9 (95% confidence interval [CI] 7.6 to 8.2) versus 6.5 (95% CI 5.1 to 7.8) hours per day.
• For all men, the youngest age group (ages 16 to 24) reported less sedentary time than the oldest age group (75 and over); 6.6 (95% (CI) 6.3 to 6.9) hours per day versus 7.4 (95% CI 7.2 to 7.6) hours per day.
• For all men, the age group between 45 and 54 reported slightly more (24 minutes more) sedentary time than the oldest age group; 7.8 (95%CI 7.6 to 8.0) versus 7.4 (95% CI 7.2 to 7.6) hours per day.
• For all women, the oldest age group (75 and above) reported more sedentary time than those aged between 16 and 75 (7.4 (95% CI 7.2 to 7.6) versus 6.6 to 6.9 (95% CI 6.4 to 7.1) hours per day).
• For men not in work, most age groups reported less sedentary time than those aged 75 and above. The exception was those aged 45 to 54 who reported more sedentary time than the 75+ age group; 7.7 (95% CI 7.2 to 8.2) versus 7.4 (95% CI 7.2 to 7.7) hours per day.
• For women not in work, all age groups reported less sedentary time than those aged 75 and above, with the lowest being in the 25-34 age group.

At the weekend:

• Those aged 25 to 54 reported the lowest amount of sedentary time (5.2 to 5.7 (95% CI 5.0 to 6.0) hours per day, compared to those over 75 who reported sedentary time at the weekend as between 7.3 and 7.4 (95% CI 7.1 to 7.7) hours per day.

How did the researchers interpret the results?

The authors conclude that their "results challenge the conventional understanding that older adults in Scotland report the highest levels of sedentary time, as the majority of middle-aged adults reported similar levels to older adults. In light of these results, we suggest changing the way national prevalence estimates are calculated for Scotland and England, so that they include sedentary time at work."

They further add that "interventions to reduce sedentary time should consider differences in the relative contributions of ST [sedentary time] behaviours by age and work-status."

Conclusion

The results of this large Scottish survey indicate that for adults in work, time spent being inactive during weekdays is greater in all age groups compared with people aged 75 and above. This is reversed at the weekend.

This indicates that work has a huge impact on activity levels. The authors argue that long periods spent sitting at work have public health implications, including increased risk for cardiovascular disease, diabetes and some cancers.

However, there are a number of limitations to the study:

• The responses were self-reported, so might be subject to bias if people inaccurately estimate the amount of time they are inactive. However, this is not likely to change a great deal between age groups. Recall bias could well lead to underestimation of the amount of sedentary time so the problem could actually be worse than described.
• Other sedentary activities that are not specifically mentioned in the survey might be overlooked and under-reported. For example, people in younger age groups may spend more time sitting down driving but as this was not specifically asked they might not report it.
• The survey only had Scottish respondents and therefore may be less relevant for a UK-wide population in which activity in different age groups might differ.
• In younger age groups, more women than men reported not working, which might have affected overall results.

While it can be challenging to fit a regular exercise regime into a 9-5 lifestyle, it is possible, especially if you make an extra effort to get active during the weekend.

Read more advice about how to increase your activity levels.

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Sitting....

"Spending just 20 minutes less sitting a day reduces blood sugar levels, improves cholesterol AND even makes you more muscly," is the Mail Online's overly optimistic claim.

Researchers in Finland recruited people who worked in offices and had young children for a study investigating whether training could help cut the amount of time the parents spent sitting. Regular, prolonged periods of sitting puts people at risk of developing diseases such as diabetes and heart disease.

Despite a programme of counselling and a lecture aimed at making people more active during work and leisure hours, people sat for only 21 minutes less for every eight hours during the first three months of the study, and only during leisure time. By the end of the year-long study, people were only sitting for 8 minutes less than those in the control group.

Researchers reported "some small positive changes" in blood sugar during the first three months, and in cholesterol biomarkers and lean leg mass at the end of the study, compared with parents who had not received the intervention. It's not clear how clinically important these changes were.

While it's true that every little helps, there's very much a dose-dependent relationship when it comes to the benefits of exercise: the more you do, the more you benefit.

You should aim to at least meet the minimum physical activity guidelines for adults.

Where did the story come from?

The study was carried out by researchers from the University of Jyväskylä in Finland. It was funded by the Finnish Ministry of Education and Culture, the Ellen and Artturi Nyyssönen Foundation, the Juho Vainio Foundation and the Yrjö Jahnsson Foundation. It was published in the open-access, peer-reviewedPLOS One medical journal so is free to read online

The Mail Online's interpretation of the study does not stand up to much scrutiny.

The 20-minute figure cited in the headline was sustained for only three months and, rather than making people "more muscly", lean leg mass stayed about the same in people who were on the programme. It's just that those who weren't on the programme lost lean leg mass.

Reduced blood sugar levels lasted only three months, and the changes in proteins related to cholesterol metabolism were small and of uncertain importance.

What kind of research was this?

This was a cluster randomised controlled trial (RCT). In cluster RCTs, groups of people are randomised, rather than individuals. In this case, neighbourhoods in the Finnish city of Jyväskylä were randomised, with the people living in them recruited to either the control or intervention arm of the study. RCTs are usually good ways to measure the effect of an intervention.

However, in this study, the intervention – a lecture and counselling about reducing sedentary time – was not "blinded". People knew whether or not they were receiving the lecture and counselling, which reduces the reliability of the results.

What did the research involve?

Researchers picked 14 neighbourhoods in the city of Jyväskylä, with seven randomly assigned to receive the intervention programme and seven to act as controls.

They recruited parents who had children aged three to eight in kindergartens and infant schools in the 14 neighbourhoods. The parents were recruited either individually or as pairs. There were 133 participants overall, with 71 parents from the intervention neighbourhoods and 62 from the control neighbourhoods.

Parents from the intervention neighbourhoods underwent the study programme of a lecture followed by counselling sessions. Researchers looked to see how activity levels and sedentary time changed over a year, and whether physical assessments also changed.

Everyone had a physical assessment and tests, including measurements of physical activity, at the start of the study, and after 3, 6 and 12 months. These included body composition, blood pressure, and blood tests to measure insulin resistance, cholesterol and blood sugar.

People were excluded from the study if starting body mass index was above 35 (which could be considered as being morbidly obese if they had other health problems), they were pregnant at the start of the study, they had long-term illnesses or if the child had a disability that delayed their development of movement skills.

Diet was assessed through participants keeping diaries for three weekdays and a weekend day at the beginning and end of the study, and on a weekday at three, six and nine months.

The intervention group's lecture explained the potentially harmful effects of being too sedentary. During counselling sessions, parents set goals to reduce their sedentary time at work and at home. During follow-up phone calls, they discussed their progress towards the goals and any problems they'd had achieving them.

The researchers compared the difference between the change from baseline between parents in the intervention and the control groups for:

• total sedentary time
• work sedentary time
• weekday leisure sedentary time
• weekend leisure time
• light activity time
• moderate to vigorous activity time
• breaks from sitting per hour during sedentary time

These were measured by giving people an accelerometer to wear (a device similar to a fitness tracker) for seven days at five points during the study year.

What were the basic results?

After three months, parents who went through the programme showed no changes in their total, workplace or weekend sedentary time compared with parents in the control group, but they were doing better on weekday leisure time:

• Compared with the control group, for every 8 hours, they sat for 21.2 minutes less (95% confidence interval [CI] -37.3 to -5.1).
• After 12 months, they were sitting for just 7.9 minutes less than the control group (95% CI -24.0 to 8.3). This difference wasn't statistically significant – it could have been down to chance.

In the first three months, the programme group did more moderate to vigorous physical activity than the control group, but that was because the control group's levels of activity dropped, not because the programme group did more activity.

There were a few differences in people's biochemical and physical test results.

Out of 12 tests of body composition and blood pressure, there was only one difference (lean leg mass, or muscle) between the groups after 12 months. However, this was mainly because the control group had lost muscle, whereas the programme group's stayed about the same (mean difference between groups 0.48%, 95% CI 0.18 to 0.77).

Of 14 biochemical test results, only two – involving levels of a protein called apolipoprotein A1, related to the metabolism of cholesterol – showed a difference between the two groups after 12 months.

How did the researchers interpret the results?

The researchers said their results showed their intervention "induced a small beneficial intervention effect on weekday sedentary leisure time throughout the whole year". They added that "some small positive changes in biomarkers were observed" at the same time.

They also noted that the initial decrease in overall sitting time achieved in the first three months of the study was not maintained over the year.

Conclusion

Despite the encouraging headlines, the study showed it isn't easy to get people to reduce their overall sedentary time. It's interesting that people were better able to make changes at home – especially when both parents had been through the programme – than in the office.

Future programmes could look at whether workplace interventions, which might include group activities or changes to the office environment, are more successful at reducing time spent sitting.

We don't know the clinical significance of the small changes in some of the physical and biochemical results found in the programme group.

It's surprising that any changes were found at all when the difference in activity levels was so small. One possibility is that the small number of participants and the large number of tests threw up some misleading results.

There are several other limitations to the study:

• It was subject to selection bias. Only 30% of people contacted showed any interest in participating, meaning those who did were likely to be more motivated in the first place, so the results may not be applicable to the general population.
• People may have changed their usual activity level when wearing the accelerometer.

Any effort to help people become less sedentary is to be applauded, but it's likely most people will need to do more than just sitting down for a few minutes less to make a big difference to their long-term health.

While 20 minutes more exercise a day is certainly better than none, if you have been inactive for a while, you should aim to gradually build up your activity levels until you meet the recommended minimum for adults.

Read more advice about getting started with or returning to exercise.

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