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Sit less and stand more to improve heart disease risk factors

and trim waistline, urge researchers

Caroline White

Friday, 31 July 2015

Sitting less and standing more is linked to lower blood glucose, blood fats, and cholesterol levels, finds research* published today in the European Heart Journal.

Replacing time spent sitting with time walking could have added benefits by helping to trim the waistline and lower body mass index (BMI).

The study adds to an accumulating body of research to suggest that prolonged bouts of time spent sitting are harmful to health.
 
The Australian researchers gave activity monitors to 782 men and women, aged 36-80, all of whom were taking part in the Australian Diabetes, Obesity and Lifestyle Study.

The monitors tracked how long each participant spent sleeping, sitting or lying down, standing and stepping (including walking and running).

After providing blood samples and measurements of their blood pressure, height, weight and waist circumference, participants each wore an activity monitor on their thigh for 24 hours a day for seven days.

The researchers then used a statistical technique called isotemporal analysis to estimate the potential impact on health of replacing sitting time with standing or stepping time.

Isotemporal substitution analysis simultaneously models the specific activity being performed and the specific activity being displaced in an equal time-exchange manner, while keeping waking hours unchanged.

An extra two hours a day spent standing rather than sitting was associated with approximately 2% lower average fasting blood sugar levels and 11% lower average triglycerides.

Extra standing time was also associated with 0.06 mmol/l higher average levels of high density lipoprotein (HDL), and a 6% lower average total: HDL cholesterol ratio. 

Replacing two hours a day of sitting time with stepping was associated with an approximately 11% lower average BMI and a 7.5 cm smaller average waist circumference.

Furthermore, average blood sugar levels fell by approximately 11% and average triglycerides by 14% for every two hours spent walking rather than sitting, while HDL cholesterol was 0.10 mmol/l higher. There was no significant effect on BMI or on waistline circumference of replacing sitting time with standing.

Dr Genevieve Healy, senior research fellow at the School of Public Health, The University of Queensland, Australia, who led the study, said: “While the study cannot show that less time spent sitting causes the improvements in these markers of health, the associations it reveals are consistent with what is known already about the benefits of a non-sedentary lifestyle. More work is needed to understand cause and effect.”
 
But she added: “These findings provide important preliminary evidence that strategies to increase the amount of time spent standing or walking rather than sitting may benefit the heart and metabolism of many people.”

Standing could be encouraged in the workplace with interventions such as sit-stand desks, she said.
 
“It is important to say that not all sitting is bad; but if people can incorporate alternatives to sitting wherever possible, it may benefit their heart and metabolic health. Our message is: ‘Stand Up, Sit Less, Move More’,” she continued.
   
In an accompanying editorial**, Professor Francisco Lopez-Jimenez of the Mayo Clinic and Mayo College of Medicine, Minnesota, USA, writes that the study “provides an important addition to the wealth of scientific evidence highlighting the importance of avoiding sedentary behaviour”.

He adds that “the fight against sedentary behaviour cannot be won based only on the promotion of regular exercise” and that while exercise should continue to be recommended, it is important to promote non-sedentary behaviour in everyday life.

“A person walking while at work for two hours, standing for another four hours, and performing some daily chores at home for another hour will burn more calories than jogging or running for 60 minutes,” he said.
 
Sedentary behaviour and environments that promote it are “seen as a sign of progress and economic power,” but the unintended consequences of modern life promoting sedentary behaviours can be reversed.

“Health care providers, policy makers, and people in general need to stand up for this. Literally,” he concluded.


* Genevieve N. Healy, et al. Replacing sitting time with standing or stepping: associations with cardio-metabolic risk biomarkers. European Heart Journal, July 2015. DOI: 10.1093/eurheartj/ehv308

** Francisco Lopez-Jimenez. Standing for healthier lives—literally. European Heart Journal, July 2015.DOI: 10.1093/eurheartj/ehv356

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