Sedentary behaviour in the workplace

First of all, I’d like to wish a happy blog-versary to Peter; today marks 6 years of blogging at Obesity Panacea in its various forms (the traditional gifts are apparently candy and iron).  To be fair, I actually forgot (but he did not), and this is my public way of making amends.  Thanks also to the readers that have followed us over the years.

On a completely separate note, below is a video of a recent webinar on sedentary behaviour in the workplace, organized by the Physical Activity Resource Centre in Ontario. In the video, I discuss the health impacts of sedentary behaviour, as well as the reasons why sedentary behaviour is bad for health (my presentation begins around the 6 minute mark).  I put together some (in my opinion) pretty nifty power point animations outlining the mechanisms that link sitting with chronic disease risk.

Also presenting in the webinar was Jennifer Jenkins-Scott, a Health Promotion specialist from the Halton Region Health Department.  Jennifer discusses ways that organizations can help their employees reduce their sedentary time.



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Could smoking cigarettes make you a better runner?

(Image source)

A few years ago the Canadian Medical Association Journal published a fascinating article by Ken Myers discussing the (as-yet unexamined) benefits of cigarette smoking on endurance running performance.  Ken is a friend and elite distance runner (we used to literally run with the same crowd while I was doing my undergrad in Calgary) so I was very excited and a bit confused when I saw his article.  Could smoking really be beneficial for distance runners like myself?

Here are Ken’s arguments:

  1. Serum hemoglobin is related to endurance running performance.  Smoking is known to enhance serum hemoglobin levels and (added bonus), alcohol may further enhance this beneficial adaptation.
  2. Lung volume also correlates with running performance, and training increases lung volume.  Guess what else increases lung volume? Smoking.
  3. Running is a weight-bearing sport, and therefore lighter distance runners are typically faster runners.  Smoking is associated with reduced body weight, especially in individuals with chronic obstructive pulmonary disease (these folks require so much energy just to breath that they often lose weight).

In the discussion, Ken goes on to point out that:

Cigarette smoking has been shown to increase serum hemoglobin, increase total lung capacity and stimulate weight loss, factors that all contribute to enhanced performance in endurance sports. Despite this scientific evidence, the prevalence of smoking in elite athletes is actually many times lower than in the general population. The reasons for this are unclear; however, there has been little to no effort made on the part of national governing bodies to encourage smoking among athletes.

Now at this point I assume that people are wondering how something this insane came to be published in a respected medical journal (at the time the article was published, CMAJ was ranked 9th of out 40 medical journals, with an impact factor of 9).  The answer, of course, is that the point of Ken’s article was to illustrate how you can fashion a review article to support almost any crazy theory if you’re willing to cherry-pick the right data.  Here is the paper’s abstract:

The review paper is a staple of medical literature and, when well executed by an expert in the field, can provide a summary of literature that generates useful recommendations and new conceptualizations of a topic. However, if research results are selectively chosen, a review has the potential to create a convincing argument for a faulty hypothesis. Improper correlation or extrapolation of data can result in dangerously flawed conclusions. The following paper seeks to illustrate this point, using existing research to argue the hypothesis that cigarette smoking enhances endurance performance and should be incorporated into high-level training programs.

While people might be able to spot the implausibility of smoking improving distance running performance, it’s a lot harder to spot with more specialized topics.  For example, if I were to argue that “Intervention X” influences body fat distribution and pulled together a few mechanistic resources supporting my arguments, it would be very difficult for an educated lay-person to know if my arguments were sound or not.  Which unfortunately is the situation almost all of us are in, anytime we read anything that is even slightly outside of our own area of research.

Even with systematic reviews, which are the highest form of scientific evidence, there is still a lot of room for subjectivity. You can develop a systematic review in a way that makes it more or less likely that you will find a certain outcome, just as you could with an individual study. Not only that, but the review depends on the objectivity of the people screening articles, who could (intentionally or accidentally) systematically include or exclude articles that may have an impact on the review’s ultimate conclusions.  And then of course the authors have to synthesize data and come to conclusions, both of which are mostly subjective activities.

That doesn’t mean that there is always a nefarious intent on the part of researchers – I would argue that there almost never is.  But take the phenomenon of “White Hat Bias“, where researchers distort “information in the service of what may be perceived to be righteous ends”. And even the most objective and ethical researcher is still going to be looking at data through their own world-view, which may cause them to miss something that is in the data, or to “see” something that isn’t really there.

The point being that whether you’re reading a blog post or a systematic review paper in a prestigious medical journal, you really do need to be skeptical at all times.


ResearchBlogging.orgMyers, K. (2010). Cigarette smoking: an underused tool in high-performance endurance training Canadian Medical Association Journal, 182 (18) DOI: 10.1503/cmaj.100042


Today’s post was originally published in November of 2011.

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Can you build up a tolerance to ice cream?

ice-creamIn essence, yes.

Research suggests that those individuals who frequently eat a given highly palatable food derive less satisfaction from the subsequent consumption of that same food, such as ice cream.

In the study, published at the American Journal of Clinical Nutrition, researchers assessed the frequency with which the adolescent study participants ate specific types of foods, including ice cream, chocolate, and many others.

Next, each participant was fed either an ice-cream milkshake or a tasteless solution while the activity of their brain was surveyed via functional MRI. The researchers were looking to see if the brain regions previously associated with food reward were activated in response to the tasty shake.
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Dear Maclean’s: Public health agencies should prioritize public health based on evidence, not fear

I came across an editorial in Maclean’s this weekend which was both surprising and disappointing (and at times condescending).  The gist of the editorial was that public health agencies like the World Health Organization (WHO), Centers for Disease Control and Prevention, and Public Health Agency of Canada, should focus on infectious diseases (Ebola, smallpox, SARS, etc), rather than chronic diseases (heart disease, diabetes, cancer, etc).

I like Maclean’s, and read it regularly.  In fact, I was disappointed specifically because their science and medical coverage is so consistently excellent.  The now-retired Science-Ish column, written by current Vox contributor and Knight Science Journalism Fellow Julia Belluz, was a fantastic model of high profile science/medical communication.  Health feature writer Kate Lunau is also great. Everything I know about Polish democracy, I owe to Maclean’s political writer Paul Wells. So while Maclean’s is typically a great, evidence-based read, this editorial was neither.

Let me begin by saying that I’ve been appalled at how slow the response to the Ebola epidemic has been.  Before I get to the editorial, I would like to urge everyone to consider donating to Medecins sans Frontieres, who are coordinating much of the Ebola response.  There’s no question this is an important health issue that demands attention. However, I fail to see how prioritizing focus on infectious diseases over the long term at the expense of chronic disease will improve health (especially in developed nations).

Ok, now to my complaints. Below are my arguments, along with excerpts from the editorial (emphasis mine throughout).

Ebola vs cigarettes

From the editorial:

More than 4,500 Africans have died of Ebola to date. The number of new infections is doubling every month. Health facilities in hot-zone countries Guinea, Liberia and Sierra Leone are overwhelmed and understaffed. And while Canada has so far been lucky in avoiding infection, on Sunday, U.S. President Barack Obama mustered the Pentagon into the fight after the botched response by civilian authorities left the American public nervous. Meanwhile, the head of the World Health Organization (WHO)—the UN body meant to provide leadership during international health emergencies—has bigger things on her mind.

Last week, as the Ebola crisis deepened, the director-general of the WHO, Margaret Chan, was in Moscow hosting a conference on tobacco control. “Yes, Ebola is truly an issue of international concern,” she told the Wall Street Journal. “But tobacco—if we put the evidence on the table—tobacco control is still the most cost-effective and efficient way of reducing unnecessary diseases and deaths arising from using such harmful products.” The conference concluded with an agreement on the necessity for ever-higher tobacco taxes. (Canada and the U.S. boycotted the assembly because of sanctions against Russia.)

 Ebola may be scary, but cigarettes are scarier.

While diseases like Ebola are terrifying, the death tolls are still relatively small compared to chronic diseases, even in many developing countries. Smoking is the # 1 preventable cause of death worldwide, and is responsible for roughly 17% of deaths in Canada.  So quite frankly, it does make sense for the WHO and other public health agencies to discuss ways to reduce tobacco related deaths, even while the Ebola response is ongoing.

Let’s put this in perspective. So far, 4,922 people have died worldwide from Ebola. In Canada alone, 37,000  died in 2011 due to tobacco use. An astounding 480,000 Americans died in 2010 from tobacco related deaths.  Put another way: tobacco kills more people than Ebola every three days. So yes, cigarettes are scarier than Ebola, at least in terms of their ability to kill.

And that’s just cigarettes. As chronic diseases account for an ever greater percentage of deaths worldwide (68% of all deaths worldwide are due to chronic disease in 2012), it seems reasonable that public health agencies give them increased attention.  By any objective measure, reductions in smoking rates, and related reduction in tobacco-related deaths are an unmitigated public health success story.

Change of focus, or lack of funding?

As Maclean’s illustrated in their cover story last week, the WHO’s inability to deal with the Ebola outbreak isn’t due so much to their focus on chronic diseases like obesity, as to the fact that their funding has been diminishing for years.  From that cover story:

The WHO has failed to provide that leadership, [Kelley Lee, a global health professor at Simon Fraser University] explains, for a “perfect storm” of reasons: an ineffective WHO African regional office, political and economic instability in the area and, most of all, because it doesn’t have the money it needs to do its job. The WHO’s regular budget has promised “zero real growth” since the 1980s, only increasing spending to account for inflation. It tightened its belt further in the late ’90s and froze the budget in absolute terms.

In contrast to their article above, the editorial implied that the reason for the spread of Ebola was because of “mission drift” towards a focus on chronic diseases.  From the recent editorial:

Unfortunately, this sort of bizarre mission drift is not unique to the WHO. Public health officials around the world have succumbed to a similar preference for tackling issues of personal choice, the free market and political causes apparently inspired by the Occupy movement. The predominant public health fixation in developed countries these days is the so-called obesity epidemic and the alleged need for food taxes, along with other intrusive measures, such as New York’s failed Big Gulp soda ban, to correct this situation.

The mandate of any public health organization is to promote health. Period.

If your goal is to promote health/reduce the risk of disease, then it makes sense to focus on whatever factors are linked to disease… be they viruses, behaviours, or income.   At some times and locations it will make sense to focus on infectious diseases, at others on chronic diseases.  As discussed below, there are some countries that need to focus on both simultaneously.

The only real argument against focusing on all disease, and all causes of disease, is that some people object ideological grounds, in the absence of data. But there isn’t a strong case to be made in terms of evidence. The Social Determinants of Health framework has shown that the environment you are exposed to have direct impacts on your health – the neighbourhood you live in, the people you associate with, your family structure, all of these can impact health in a multitude of ways. Health is not exclusively at the mercy of bacteria or viruses. This was nicely illustrated in an article published in Macleans in 2013, which included this extremely informative infographic:

Image via

And now the most confusing portion of the editorial

Last year, Toronto’s activist public health office chastised ABC TV for adding actress Jenny McCarthy, a vaccination critic, to the cast of its talk show The View. It is apparently necessary to remind public health officials that their mandate (and competency) does not include individual food choices, income disparity, trade, agricultural policy or network programming decisions.

This year has shown a tremendous spike in the number of measles cases in the US (see image below).  Most of the infected individuals were unvaccinated.  Thus, the reason that public health agencies objected to Jenny McCarthy getting a daily television platform is that she is the standard bearer of the anti-vaccine movement.  Even if public health agencies focused primarily on infectious diseases as the editorial suggests, it would still make sense for them to publicly oppose her views, and to advocate against giving her a prominent daily platform on network TV. While we cannot stop the network from hiring her, we can be outspoken critics of the dangerous views she represents, and ensure that the public understands that her views do not represent the mainstream, and in fact represent a dangerous alternate reality.

Chronic diseases are a considerable (and increasing) burden, even in developing nations.

While the leading causes of death and disease in Africa are mostly infectious in origin, their role has been decreasing, while the role of chronic diseases has been increasing. Between 1990 and 2010, the disease burden of diabetes in sub-Saharan Africa increased by almost 90%.  Only HIV/AIDS saw a greater increase in disease burden than diabetes over this period.  The burden due to stroke and heart disease also saw increases of more than 30% during that period, while  the disease burden due to respiratory infections, diarrheal diseases and malnutrition all decreased by 15-35%.  This is not to say that infectious diseases have been vanquished – HIV and malaria remain the top causes of death and disease in Sub Saharan Africa – but developing nations have the unenviable task of addressing high rates of infectious disease while also seeing increasing levels of chronic disease; a situation referred to as the “double burden” of disease.

The line between infectious and chronic diseases is blurring.  

We’re now finding out that several types of cancer (cervical, throat, etc) are linked to viruses, and are therefore in some sense an infectious disease (so too is obesity, and other disease-virus links are likely to follow).  At the same time, advances in medications have led some to suggest that HIV is essentially a chronic disease, since it can be managed more or less indefinitely with proper medications (a key characteristic of chronic diseases is that they are long lasting, typically with no true “cure”).  If public health agencies were to focus primarily on infectious diseases, would cancer be included?  Only those that are specifically linked to viruses?  What about HIV? Would that be too much “mission drift”? Or should we only focus on diseases that are dominating the news cycle at any particular point in time?

Final thoughts

Image source

Chronic diseases are much more complicated than infectious ones.  We know what causes Ebola, smallpox, and HIV.  While it’s not necessarily easy to prevent or cure these diseases, at least the process is itself relatively simple. Contrast that with the risk factors for obesity in the above graphic (a similar graphic could be made for heart disease or diabetes).  With a chronic disease it’s often difficult to even determine the key risk factors, let alone agree on the best methods of treatment or prevention.

I know that many people are ideologically opposed to public health agencies focusing on chronic diseases.  Chronic diseases are seen as being due to “lifestyle”, while infectious diseases are seen as something outside of our control.  Unfortunately there’s little evidence to support that view, and even less evidence that focusing our efforts on infectious diseases will result in better health or longevity in Canada or abroad.


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Everything you ever wanted to know about breast fat but were afraid to ask

Breast anatomy (1. Chest wall; 2. Pectoralis muscles; 3. Lobules; 4. Nipple; 5. Areola; 6. Milk duct; 7. Fatty tissue; 8. Skin) Source

Before I begin, I should admit that the title of this post probably oversells the depth and breadth of the content that follows.  In fact, this post is going to focus exclusively on the one breast-related issue on which I may be considered an expert, and that is the relationship between breast fat and metabolic risk (if it sounds like I’m bragging, I’m not).  I should also assure people that while this post does contain pictures, they are all completely safe for work.

As you can see in the above figure, fat tissue makes up a large proportion of the tissue – often the majority – within the breasts.  And from what I understand, differences in breast size are due primarily to differences in the amount of fat tissue, as opposed to differences in duct or lobule volume.  Similarly, changes in breast size due to weight loss (which can be seen in the photo at the bottom of this post) are due to reductions in the volume of fat within the breast.

Breast fat is a fascinating topic, but before we get to that specific fat depot, we need to briefly review the major types of fat within your body.  If you’ve been following our blog for a few years this issue will be old hat, so feel free to skip to the next section.

All body fat is not created equal

In contrast to what some advertisements might have you believe, the fat in our bodies is not simply sandwiched between other tissues like a layer of butter on a baguette.  Instead, fat is stored within specialized cells called “adipocytes” (hence fat is referred to as “adipose tissue”).  Regardless of your body size, everyone has adipocytes in their body (as Peter has discussed in the past, having too few fat cells is actually much worse than having too many).  When you lose or gain weight you are primarily changing the amount of fat stored in your adipocytes, rather than adding or removing actual fat cells.

The image below is taken from my Master’s thesis, which illustrates the three main adipocyte depots.  The top image is a cross section of an abdomen, while the two bottom images are cross-sections of a pair of thighs.

Key body fat depots

Visceral adipocytes – these adipocytes are found within the abdominal wall and surround the internal organs (e.g. the viscera).

Intermuscular adipocytes – these are the fat cells that are found in between your muscles. The marbling on a steak is fat stored in these intermuscular adipocytes.

Subcutaneous adipocytes – this is the fat that you can pinch directly underneath your skin.  Love handles, breasts, and anything mentioned in the song My Humps fall into this category.

The importance of this distinction is that these 3 fat depots have very different associations with health risk.  Visceral and intermuscular adipocytes are generally very bad places to store body fat.  Research has consistently shown that the more fat you store in these depots, the greater your risk of death and disease.

In contrast subcutaneous fat in the legs and buttocks actually seems to be protective against heath risk.  For example, this paper from my MSc found that people with more subcutaneous fat in their lower body are actually healthier than people with the same body weight but less subcutaneous lower body fat.  Despite being counter-intuitive, this is a very consistent finding (it made up the bulk of Peter’s PhD thesis).  It’s also the reason why an “apple” body shape (e.g. lots of abdominal fat with very little lower body subcutaneous fat) is associated with much more health risk than the “pear shape”, characterized by fat stored mainly in the hips and thighs.

I’ve borrowed the two images below from one of Peter’s slideshare presentations, which nicely summarize the contrasting effects of visceral and subcutaneous fat accumulation.

Image by Peter Janiszewski

Image by Peter Janiszewski

There are a number of reasons why visceral fat stores are so much worse than lower body subcutaneous stores – as they expand visceral adipocytes become insulin resistant and promote inflammation, while also releasing fat into the blood stream where it can do damage to other tissues like the heart and liver.  In contrast, subcutaneous adipocytes in the legs and butt tend to hold onto fat very tightly (hence why they are sometimes viewed as a “problem area” that are so difficult to slim down), which is actually quite beneficial from a health perspective.

For anyone interested in learning more on this topic, I’d recommend this previous post, or Peter’s excellent series on metabolically healthy obesity.

What is the health impact of breast fat?

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Category: News, Obesity Research, Peer Reviewed Research | 3 Comments

Do physical activity interventions also decrease sedentary time ?

Image Source 1 & 2.

Image Source 1 & 2.

Today’s post comes from friend and colleague Dr Stephanie Prince, discussing her important new paper published in Obesity Reviews (available free here).  More on Stephanie can be found at the bottom of this post.  And if you happen to be attending the Canadian Association of Cardiovascular Prevention and Rehabilitation (CACPR) conference in Vancouver this week, swing by to hear Stephanie present on Saturday in the Scientific Abstract Presentations session (details here).


Physical activity has long been established as a strong predictor of cardiometabolic health, disease and mortality.  For decades now researchers have been trying to develop interventions that will increase our physical activity levels, most notably at higher intensities – think moderate-to-vigorous physical activity (otherwise known as MVPA).  In Canada, we have physical activity guidelines which promote that adults (18-64 years) aspire to achieve a minimum of 150 minutes of MVPA per week in bouts of 10 minutes or more, with the idea that more physical activity is always better.  Canadians also have sedentary behaviour guidelines for children and youth which propose limits on screen time.

There is a rapidly growing body of literature which suggests that greater amounts of time spent being sedentary (watching TV, screen time, sitting time, total sedentary time) are associated with an increased risk for markers of cardiometabolic disease, cardiovascular disease, diabetes, some cancers and premature death (references here and here).  Sedentary behaviours refer to the time spent sitting or lying down and in a state where there is relatively minimal energy expended (not just the absence of MVPA).

While there has been a lot of research looking at the effectiveness of physical activity interventions, little has been done to examine whether these interventions also decrease the time we spend being sedentary.  Prior to this review I often wondered whether the opposite might occur whereby individuals who increased their physical activity levels may become more sedentary almost has a consequence of the satisfaction that they had already undertaken the necessary amount of physical activity needed to meet physical activity guidelines.  Although in its infancy compared to the physical activity field, the sedentary behaviour field is now proposing and testing a variety of interventions targeting sedentary behaviours exclusively  (with the majority to date having focused on office environments, where many of us spend the majority of ours days sitting at desks in front of computers).  While the efficacy of physical activity interventions is more known, it remains unknown whether these intervention also have the capacity to decrease sedentary time.  Further it is unknown whether interventions which target sedentary behaviours are any better at reducing these behaviours than physical activity interventions.

Therefore, the objective of our research was to systematically review the literature and compare the effectiveness of interventions with a focus on physical activity and/or sedentary behaviours (e.g.physical activity only interventions vs. physical activity + sedentary behaviour interventions vs. sedentary behaviour only interventions) for reducing time spent being sedentary in adults.

What did we do?

To examine all available literature we conducted a systematic review which searched six different bibliographic databases (you can see more details on this in the full article) looking for any study which described a physical activity and/or sedentary behaviour intervention and reported on changes in total sedentary time or time spent watching TV or sitting among adults. All of the studies included in the review can be found in the supplemental tables found here.  We were also very fortunate to obtain several unpublished results provided to us upon request from authors of original studies where sedentary time was captured, but not reported upon in previous articles.

We assessed the quality and risk of bias of every individual study and also used the GRADE (Grading of Recommendations Assessment, Development and Evaluation) framework, essentially the gold standard for assessing the overall quality of the evidence and for rendering a recommendation based on the current evidence.

[Travis’ note: This was a lot of work!!!]

What did we find?

Figure 1, Prince et al.

After we removed duplicate papers, we ended up retrieving 9,107 relevant papers.  That was a lot of papers to screen!  After many hours and days looking at the abstracts and then the full articles, 63 studies were kept in the review having met our inclusion criteria.  Of these 63, 33 were used in the meta-analyses which allowed us to group quantitative results to yield an overall effect of the interventions.  See Figure 1 for the PRISMA flow diagram to get a sense of how we screened out papers.

Figure 3, Prince et al. Click figure to view full size.

When we examined all of the evidence looking at both the more descriptive results of what the studies found and also at the quantitative results (see Figure 3 above) we found that on average the physical activity interventions resulted in significant, though very small reductions in sedentary time (average difference of 19 minutes/day).  When interventions had both a physical activity and sedentary behaviour component they resulted in significant, but slightly greater reductions in sedentary time (average difference of 35 minutes/day) (Figure 4). Most promising is that when interventions focused solely on the behaviour itself, they yielded an average reduction of 91 minutes/day.

Figure 4, Prince et al.

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Category: Peer Reviewed Research, Physical Activity, Sedentary Behaviour | Tagged | 2 Comments