Sitting And Mortality

A few days ago the Archives of Internal Medicine published the timely results of the effects of sitting on mortality rates. van der Ploeg and her colleagues followed over 220,000 Australians over a 3 year period. The subjects were 45 years or older and sadly 5405 people passed away during the course of the study. The researchers found that mortality risks increased with daily sitting time. Compared to people who sat less than 4 hours a day, those that sat for 4-8 hrs had a 2% increased risk of mortality. Whereas those that sat for 8-11 hrs a day increased their risk by 15% and the subjects that sat for over 11 hrs increased their risk of death by a whopping 40%!

Fascinatingly, their results revealed that prolonged sitting was a risk factor for mortality independent of physical activity. Probably because “time spent doing moderate or vigorous exercise and time being totally sedentary may affect long-term disease risks separately.”

Don’t be too depressed about it…we all have to go at some stage…but if you prefer to leave later rather than sooner, have a look at my previous post ‘I Wouldn’t Sit For That (Part 2)‘ for some helpful tips!

The Obesity Paradox

According to research, obesity is to a certain extent genetically determined. The pandemic now affects a billion people and has gradually grown over the last 150 years. Interestingly, our genes have not changed over that period. So how could obesity, which is genetically determined, have appeared over a time when our genes have remained unchanged? What has changed?

Well, over 150 years ago 90% of the population lived an agricultural lifestyle. They walked to work, performed active physical work, walked home after work. Water had to be carried and clothes washed by hand. Our lifestyles were much more similar to those of our distant ancestors in that, we stood and walked for most of the day.

With the advent of industrialisation and urbanisation 50% of the world’s population moved to the cities. This figure is even higher in developed countries. Factory work became prevalent and chair-based work replaced standing just like machine operation replaced tool use. The biggest change has taken place over the last 25 years…over half the population in the developed world now sits in front of a computer for 8 hours a day. As a result of these changes, our occupational energy expenditure could have decreased by as much as 1200 kcal/day.

At home most of us have a personal computer and we spend a few more hours banking, shopping, browsing and even socialising (Facebook, Twitter, MySpace, etc)! Oh, and if we’re not sitting in front of the computer it’s probably the television…another brilliant invention that appeared in the last century. Sales of labour-saving devices like washing machines, dishwashers and cars track obesity rates and it’s estimated that mechanisation saves  around 111 kcal/day.

Obviously food has become more available (in industrialised countries) and one could assume that our intake has increased. Surprisingly, in the UK since the 1980s, energy intake seems to have decreased whereas obesity rates have doubled! Statistics in the US show that intake hasn’t changed but obesity has skyrocketed…

Here’s a quick thermodynamics refresher…when energy is added to a system it’s either used to perform work or stored…if the energy intake is greater than the energy expenditure, the excess is stored as fat…if the energy imbalance continues over several months or years it leads to obesity. It’s becoming clear that it’s the decrease in our activity that has lead to the weight gain.

How come we haven’t all been affected by this? This is where the genetics plays it’s part. Those of us that are genetically programmed to conserve energy have blossomed in this new modern environment, the rest have found other ways to replace their need for movement: walking or cycling to work, pacing about at work, getting involved in DIY at home, going to the gym or taking part in sports or active hobbies. Crucial research shows that lean sedentary people stand and walk for about 2.5 hrs/day more than obese people. If obese individuals were to stand and walk 2.5 hrs more each day it would equate to an expenditure of 350 kcal/day which is exactly the figure that was identified in a different study to determine the amount of exercise that obese people had to undertake to help weight loss.

Why should we care about obesity? Perhaps because it’s been linked to type 2 diabetes, hypertension, stroke, arthritis, sleep apnea and cancer…maybe because obesity related medical expenses are out of control and  in the US they reached $75 billion in 2003!

What’s the best way to lose weight? Is it through exercise or non-exercise activity? Or both? According to Dr Levine, the majority of people who exercise for just under 2 hours a week expend an average of about 100 kcal/day. This is a drop in the ocean compared to what it’s possible to achieve by increasing non-exercise activity. Granted, we can’t all change our jobs and become lumberjacks or tree surgeons but we can become more active both at work and at home. Our muscles are almost completely silent when seated and as a consequence, our energy expenditure is negligible…our expenditure goes up 15% when standing and doubles when ambling…purposeful walking can double or triple it! So, spending less time sitting seems to be the key to burning up more calories.

Prolonged sitting time has been linked to metabolic syndrome, type 2 diabetes, obesity and cardiovascular disease. This is thought to be the result of poor fat metabolism due to the decreased production of lipoprotein lipase in muscles when seated. Non-exercise activity reverses this process.

It appears our technological innovations have had insidious effects on our health. The antidote lies in freeing ourselves from the chair…can we afford to wait for governments and corporations to reengineer our workplaces? Probably not…we must all take responsibility for our health and those among us that have a predisposition towards energy conservation need to take active measures by simply standing and walking about more often and for longer periods during the day.

Most of the information in this post is inspired from the work of Dr James Levine, Professor in the Department of Endocrinology at the Mayo Clinic in Rochester MN

Prolonged Sitting Affects Glucose Metabolism

New research published in the journal Diabetes Care has concluded that after meals, regular short bouts of light or moderate walking lower glucose and insulin levels. The subjects were asked to walk around for 2 mins every 20 mins. The effects of these short bouts of walking assist glucose metabolism and may reduce cardiovascular risk.

This adds to the mounting evidence regarding the health risks associated with prolonged sitting.

I Wouldn’t Sit For That (Part 2)

Here are my tips to help prevent back pain, obesity, heart disease, cancer and death from over sitting:

  • Stand whilst on public transport…there’ll be more than enough time to sit when you get to work
  • Get up from your desk at least 1-2 times an hour (less than 5 minutes standing and walking around is sufficient)
  • Drink more often, you’ll have to get up more frequently…to get a drink…and to go to the toilet
  • Rather than send an email, why not walk over and speak to someone? (research has shown that walking at a leisurely pace is enough to reverse the metabolic changes caused by prolonged sitting)
  • Don’t have lunch at your desk…go for a short walk…get some fresh air
  • Organise your work tasks so that they involve frequent movement
  • Here’s a little exercise you can do when you stand (breath in whilst you reach upwards and hold the position for about 5 seconds)…it will help your back
  • Don’t use your car when your feet will do just as well

The clear message is that health can be maintained by including frequent short periods of standing and walking in our normal daily activity…little and often is the way forward!


I Wouldn’t Sit For That

Most of us spend the overwhelming majority of our waking hours seated. We sit down to have breakfast. Then we sit in our cars or on the train or bus on the way to work. When we arrive at work, we sit at our desks until lunch and then sit a little more to enjoy lunch. After work, we once again sit in our cars or on the train or bus. As soon as we get home we rush in to “take the load off” and collapse into our sofas, from where we surreptitiously pretend to read the paper…until dinner is ready! We then sit down to savour our meal, after which we promptly return to our sofas to digest…whilst watching a little TV…sound familiar?

Unfortunately for us, sitting is a major risk factor in the development of low back pain and it has even been associated with disc herniation. I naïvely assumed that was the worst of it until I stumbled upon a thought-provoking article…

Can sitting too much kill you? Wow, talk about getting your attention! Research has shown that spending excessive periods of time sitting can lead to obesity, heart disease and cancer. This can happen even if we take part in regular exercise. As Dr Marc Hamilton says, “sitting too much is not the same as exercising too little”. One of the culprits may be an enzyme called lipoprotein lipase. It allows muscles to uptake fat thereby decreasing the levels of fat circulating in the blood stream…and preventing arteries from becoming clogged up. Sitting markedly decreases the secretion of lipoprotein lipase. A large study conducted by Dr Peter Katzmarzyk found those who sit more are at higher risk of death than those who sit less.

Shocking isn’t it? I bet you won’t complain the next time you don’t get a seat on the train or underground! Before you sell your sofa and chairs or hand in your notice in search of that coveted job as a parking attendant or postman…things may not be as bleak as they seem…check out my next post for some life saving tips!