If you go to your physician’s office and inquire about your weight status, he or she will measure your height and weight to derive your BMI (weight in kg divided by height in m squared). Then they will compare your BMI to that of established criteria to decide whether you are underweight (<18.5 kg/m2), normal weight (18.5-24.9 kg/m2), overweight (25-29.9 kg/m2), or obese (>30 kg/m2) . Often times, this measure alone determines whether or not you receive lifestyle treatment.
But how useful is this measure anyways? What does it tell you about your health? And finally, how helpful is it to measure when assessing the effect of a lifestyle (diet/exercise) intervention?
Before I get into the various limitations of BMI, I must point out that the measure is quite useful across large populations, as it is well correlated with the degree of adiposity, and of course it is extremely simple to measure in clinical practice.
Nevertheless, here are some of the key issues with BMI, particularly when used on an individual basis.
1. BMI does not differentiate between the Michelin Man and The Terminator
Ok, we might as well just get this abundantly obvious problem out of the way. I have heard countless times how one buff celebrity or another (e.g. Tom Cruise, Arnold Schwarzenegger, The Rock etc.) would be classified as overweight or obese according to their BMI due to their excess amount of muscle. Yes, this is absolutely true. BMI is a measure of relative weight; fat mass and muscle mass are not distinguished. Here’s what is equally true: the large majority of the general population with a BMI in the overweight or obese range does not look like Jerry Maguire or the Terminator. Also, if you seek advice from your physician about your “excess weight”, in case you have body dysmorphia and cannot yourself decide, they will quickly be able to assess whether your excess weight is due to your bulging muscles or your rolls of adipose tissue. So while this is an obvious problem, I would argue not the main issue. Continue reading »
Travis’ Note: Today’s guest post comes from our friend and colleague Atif Kukaswadia, aka Mr Epidemiology. You can find more on Atif at the bottom of this post.
I’d like you to watch that video [email subscribers can view the video by visiting the blog itself]. After watching it, tell me you’re not fascinated by what Neil deGrasse Tyson says. I’ve seen a few interviews he’s done, and every time I leave shaking my head and being completely blown away. Excitement and passion is contagious, and seeing someone be that energized about their work can influence the way you think about a topic, encouraging you to further explore that field. Nowhere is this more valuable or noticeable than in STEM careers and school-aged youth (STEM = Science, Technology, Engineering and Math).
Role models are an important part of life. When you’re a kid, there are always people you look up to, who, in your 10 year old mind, are the most amazing people in the history of the world. They can make you interested in an area you otherwise wouldn’t consider, or make you take guitar lessons to learn the guitar solo from Sweet Child O’ Mine (a young Mr Epidemiology really liked rock music). Role models can range from professional athletes to business people, and include parents and older siblings. But while there are lots of athletes, musicians and movie stars who can be considered role models, how many science role models are there?
With the exception of your middle or high school science teacher, how often would a child interested in science have a chance to interact with a real scientist? This blog post from Sociological Images highlights how a sample of seventh graders view scientists. In short, we all wear lab coats, have crazy hair and live in our own world. I don’t know about you, but I haven’t worn a lab coat since undergrad – my SAS code isn’t going to spill all over me. A lot of youth don’t understand what we do, and more importantly, the range of what it is we do.
There are some “famous” scientists including Bill Nye, Carl Sagan and Neil deGrasse Tyson (featured in the video above), and there have been attempts to make scientists more interesting and accessible, such as the Rock Stars of Science Campaign and Science Cheerleaders. But how often do youth get to actually talk to them? And do youth ever get a chance to meet them?
Not likely. But you can help.
As someone in a STEM career path, you can talk to youth about your experiences and encourage them to consider a future in STEM fields. There are a myriad of programs aimed at bringing science to life for youth.Let’s Talk Science and Actua are both STEM-based outreach programs, where undergraduate and graduate students are paired with teachers to go into classes and give a talk. CIHR has the Synapse program that will send you regular emails about upcoming mentorship opportunities in your area. Being on the mailing list doesn’t obligate you to participate, but if you see something interesting, you can volunteer your time.
In addition, currently, school boards across Canada and the US are gearing up for Science Fair season. Young, impressionable minds are putting together posters and displays, collecting data all in the name of science and preparing talks to explain what they did.
And those fairs need judges.
Most of my readers are in university in some capacity – ranging from first year undergraduates all the way to new investigators. I encourage you to find a science fair near you, and volunteer an evening to help judge those programs. Tell your friends, make an evening of it – go judge posters and then go for drinks afterwards! My research group has sent a few people for the past two years, and we always leave blown away by how innovative these youth are [Peter's note: I did this for a few years while in grad school as well and it was always a wonderful time. Some of these kids are brilliant!]
In particular, I would like to encourage my female colleagues to volunteer at these events. There has been a lot of work looking at why there are fewer females than males inSTEMcareers. As a female in those fields, you can have a conversation with these young researchers that male scientists simply cannot, either through the activities above, or through organizations set up specifically toencourageyoung girlstoconsiderSTEM careers. I can’t comment on this issue myself, so for a better understanding, here are some great pieceson thisimportantissue. The Sociological Images link above raises an interesting point about this: Girls were asked to draw a scientist before and after meeting one. Before meeting a scientist, only 36% of girls drew a female scientist, and this increased to 57% after meeting a scientist.
As a student in a STEM field, you’re uniquely positioned to help stimulate curiosity and foster interest among youth. Many of us wouldn’t be here if we didn’t have a mentor or someone who encouraged that passion when we were that age, and it is our responsibility to pass that onto the next generation of young scientists.
I’m going to leave you with this quote from Neil deGrasse Tyson (if it wasn’t already clear, he’s my science idol):
The best educators are the ones that inspire their students. That inspiration comes from a passion that teachers have for the subject they’re teaching. Most commonly, that person spent their lives studying that subject, and they bring an infectious enthusiasm to the audience.
— Neil deGrasse Tyson
Do you know other ways young researchers and students can mentor school-aged youth that I’ve missed? Let me know in the comments!
Atif Kukaswadia
About the author: I’m an Epidemiologist. Well, I’m learning how to be one – I’m currently doing my PhD. Contrary to popular belief, that doesn’t mean I’m a skin doctor. Epidemiology is a broad field that encompasses methods and techniques used to address issues that affect populations. Or, put more eloquently “Epidemiology is the study of the distribution and determinants of disease, and disease related states, in a population of individuals.” In short – we study who is getting sick, what is making them sick, and how sick they are getting. You can replace “sick” with any health outcome there, and there’s an epidemiologist looking at it. We do other stuff too, but that’s a story for another day. He blogs at MrEpidemiology.com, and can be found on twitter @MrEpid.
Over the past few days, a number of people have sent me a video of the push-up competition that went down on the daytime show, Ellen, between the show’s host and the first lady, Michelle Obama.
Although one of the women technically did a greater number of push-ups, quite the debate has arisen online surrounding the form used in performing the exercise.
To be perfectly honest, regardless of how ideal their form may have been, for women in their late 40′s to mid 50′s to easily do more push-ups (a very popular exercise among men) than most guys in their 20′s and 30′s is certainly inspiring – not to mention intimidating.
Check the video for yourself:
(Note to email subscribers to click on the title of the post to log onto the site to view the video)
The past few months have been great for media coverage of sedentary behaviour, and I’ve been fortunate to be on the receiving end of a few interviews. I thought it would be fun to put them up here on the blog, so today I have 4 different clips – 2 video and 2 audio (email subscribers can view the videos by clicking on the title of today’s email).
The first video clip is from an interview with CTV News Channel, which I did in early December. I was in Ottawa while the hosts were interviewing me from Toronto, so my only connection to them was an earpiece (ps – do they wash those things between interviews?). I was asked to stare directly into the camera, which is a bit intimidating to say the least! My mother especially likes this clip as the interviewer was really challenging me on my answers, which kept me on my toes. Unfortunately most journalists want a concise answer for “how much sedentary time is too much”, and so far we just don’t know much more than “people who sit less are healthier than those who sit more”. Apologies for the bootleg quality of the first video, it’s the best we could do!
The next two clips come from my visit to New Brunswick earlier this month. I was in town visiting my parents for the holidays, and had the opportunity to give a guest lecture at the University of New Brunswick Fredericton campus. The talk was open to the public, and we were fortunate to get a surprising amount of media attention focusing on sedentary behaviour research leading up to the event.
Below are two reports (one from CBC Radio, and one from CBC TV) that came out the day of the talk, which may be of interest to those of you interested in sedentary behaviour. The reports cover the field in general, as well as a bit of info on my thesis project itself, which I haven’t discussed much here on the blog (I’m asking kids to sit for extended periods of time, then looking to see if that has a measurable impact on their metabolic health). I also demonstrate the pedal machine I use when working in the student lab, including my patented “backward pedaling” technique, which for some reason makes it much easier to pedal without whacking my knees on my desk (this is a relief not only for my knees, but also for my labmate Richard who has to put up with my pedaling).
Of note, the CBC TV piece was actually picked up and re-aired on CNN. You can expect to see an “As seen on CNN” logo on Obesity Panacea in the near future (look out, Fireyourfat.com!).
As a bonus, the TV spot also features a short clip of me juggling as a 13 year-old, back from my days a professional street performer (more than once in my life I have benefited from a slow news week in Fredericton). Also, the trophies in the background of the interview shots belong to my father, a 3-time Canadian baseball champion (my wife was disappointed to find out they weren’t mine!).
Unfortunately I’ve had a hard time embedding the radio interview here on the blog, but it can be heard at the following link: CBC radio interview.
Finally, a bonus clip from a podcast I recorded last week with the guys from 1 Meal, 1 Workout (my interview starts around the 10 minute mark). You can download the clip here, or subscribe to their podcast in itunes.
Travis’ Note: Today’s guest post comes from Registered Dietitian Julie Rochefort, in response to my post last week titled “Time to Watch My Weight“? More information on Julie can be found at the bottom of this post. On a personal note, I should add that I don’t believe that weight loss is always a bad goal, but nor do I think it’s the solution for all individuals. Enjoy the post!
PS. For those interested in the Health at Every Size Movement and the treatment of obesity, we will be hosting a debate in Ottawa in June of this year on the topic “Is Obesity a Disease?”, with two prominent speakers looking at the pros and cons of the medicalization of obesity, among other things. More details on that event coming soon.
The Problem
As a frequent flyer within the twitterverse (@julie_rochefort; @shift_the_focus), I came across Travis’s tweet which indentified a very pressing and ethical issue facing health care practice today: weight bias.
my bmi is <25. at my physical, the nurse [asked] me to “watch my weight”, lest it should eventually increase to 25
The Issue
Subsequently in his post, Travis questions why his nurse focused on his weight rather than other relevant health behaviours such as, food intake and physical activity. While I cannot speak from a nursing perspective (albeit, there are many commonalities among health care professions); I argue that the way in which obesity is framed and discussed within healthcare professional education may help to explain the maintenance of the acceptable weight=health mentality.
The Dietitians’ View
During my professional development in dietetics, dietitians were identified as a key player in the national fight against obesity; which in turn defined our role as weight loss “experts”. Accordingly, during my education and training, I was taught and mastered, how to calculate the BMI and, appropriately classify individuals into their respective weight categories. Normal. Overweight. Obese. Obese Class I, II, III. Once classified, I was expected to ensure those in the normal category maintained their weight and the fat people lost weight. Failure to keep individuals within the supposedly safe BMI range of 18.5-24.9 would question my duties as a professional and put my patient’s health at risk.
While research continues to demonstrate that obese individuals can improve metabolic indicators (e.g. high blood pressure, high cholesterol, insulin resistance and glucose intolerance) independent of weight loss (Bacon and Aphramor, 2011), why is there still such a focus on weight at the clinical level?
Critical Obesity Studies
The weight-centered approach to health was a singular focus of my professional education and training. I wasn’t introduced to an alternative way of interpreting the weight/weight-loss imperative until my second semester of graduate school. Why was this alternative view not incorporated as part of my professional education? Perhaps dietetic educators can help shed some light on that question.
The overstated associations between weight and the risk of disease have given us permission to correct and pose shame onto the fat body defined by a BMI >25. While Travis was able to overlook the well-intended warnings from the nurse, unfortunately this is likely not the norm.
While clinicians often practice with the best of intentions, a shift away from promoting weight-loss needs to occur if we are to truly commit to our ethical responsibility to ‘do no harm”.
The Next Steps
Incorporating alternative views of fatness is imperative to promoting the health and well being of the population. I am not sure how this shift will take place. A good way to start this shift is by questioning our traditional approaches to body weight and engaging in dialogue with all members of the health care team, including the patient.
Julie Rochefort is a Health at Every Size (HAES) Registered Dietitian and recent graduate from Ryerson University’s Masters in Nutrition Communication program. Her research interests involve examining weight bias and size discrimination and the impacts on health.
Shikany, J., Thomas, A., O. McCubrey, R., Beasley, T., & Allison, D. (2011). Randomized Controlled Trial of Chewing Gum for Weight Loss Obesity DOI: 10.1038/oby.2011.336
[Update: For the clinical perspective on today's topic, check out the accompanying article on Dr Yoni Freedhoff's blog Weighty Matters]
I had an interesting experience at my last physical exam, and I thought it would be worth sharing here on the blog. Before the physical a nurse put me through an eye test, then took my blood pressure, height and weight. She then calculated my BMI, and told me that I was in the “normal range” (it was around 24.5). But, she continued, I was pretty close to the overweight cut-off of 25.0, so I should “watch my weight” moving forward.
I said “un-huh” and sort of laughed inside my head, given that I’m an obesity researcher and we have written the oddpostaboutBMI here on Obesity Panacea. But the more I talked about the episode with other people, the more ridiculous it seemed. Here’s why.
BMI is only one aspect of health
As we have said before,weight ≠ health. BMI is moderately useful at estimating body fat, and therefore health risk (especially at the population level). However, as Peter and I have argued many times, your behaviour matters as much (or more) than your weight when it comes to health. If you are physically active and eat a healthy diet, you’re likely to be relatively healthy whether your BMI is 22 or 32. It’s not that weight doesn’t matter at all, but it’s far from the only thing that matters.
(For more on the relationship between BMI and health, I suggest this excellent post by Peter while Obesity Panacea was hosted on Scienceblogs. Or, for a review paper on the health-benefits of exercise regardless of body weight, click here.)
Context matters
My weight has been stable for several years. I am (extremely) physically active. I try to limit the amount of time I spend sitting. And thanks to my wife’s positive influence, I eat a reasonably healthy diet (mostly homemade vegetarian food for breakfast and supper, with leftovers and/or pizza for lunch). My metabolic health is also fine although, ironically, I had to specifically ask before I was be told my HDL and triglyceride levels.
Why would you counsel a weight stable person with a BMI in the healthy range about their weight (as opposed to their behaviour) anyway? I’m certainly not the only person to have this experience – here’s what colleague Atif Kukaswadia had to say on twitter:
My BMI is around 24.9. My doc told me to “not gain any more weight” for the same reason.
Yet, as our science blogging friend DrugMonkey pointed out on twitter, none of that means that we’re going to be weight stable forever. I’m in my late 20′s, cutting back on my participation in competitive sports, recently married, and nearing the end of grad school. It wouldn’t be at all surprising if someone in my position were to begin putting on a few pounds over the next few years. In that context, the nurse’s advice seems to make perfect sense.
Except for one (very big) oversight.
How do you “watch your weight”, anyway?
This is really the crux of the problem. Weight is an outcome, not a behaviour. When someone tells you to watch your weight, what do they really mean?
Obviously one would assume that the nurse meant that I should be physically active and eat a healthy diet. Except she didn’t say anything about either of those things. She didn’t ask about my level of activity or my diet (although it had been recorded during an earlier visit), nor did she give me any counseling on what a healthy diet should look like.
as I have said before, all weight loss attempts should be medically indicated and anyone attempting to lose weight needs to be warned that they may in fact be increasing their long term risk of becoming (even more) overweight or obese.
I don’t want to be too harsh on the nurse because she clearly meant well. But a clinical strategy that focuses exclusively on body weight, with no information or counselling related to healthy behaviours, and completely ignoring all context, is almost certainly going to fail (and possibly make things worse than they were at the beginning).
As always, I’m curious to hear what others think. Has anyone had a similar experience? Have a different perspective on the nurse’s advice? I’d love to hear about it in the comments section. And don’t forget to check out Dr Freedhoff’s thoughts on the issue over at Weighty Matters.
There is an interesting article today at the Sedentary Behaviour Research Network examining a new study suggesting that TV watching may lead to reduced fitness in children.
The article was written by our colleague Ash Routen, and here is his take-home message:
…it appears for most children that increased time spent engaged in screen-based SB may lead to lower cardiorespiratory fitness (CRF), regardless of how much PA they engage in. However the negative associations reported were not stable across the CRF distribution. That is, there appeared to be no significant relation at the lower end (10th percentile) in boys and girls, and at the upper end (90th percentile) in boys.
The authors speculated that genetic predisposition may account for this non-uniform association, with some individuals at the lower end of the CRF distribution displaying a resistance to age and SB driven changes in CRF.
You can find the full article (as well as the world’s largest database of sedentary-behaviour related research) on the Sedentary Behaviour Research Network website.
Today I’d like to take a moment and share something a bit more personal than we normally do on Obesity Panacea.
I hope you don’t mind my straying off topic.
When Travis and I started blogging back in 2008, we were sharing a small office at Queen’s university; Travis was just finishing up his Master’s and I was midway through my PhD.
Since that time much has changed for both of us.
For instance, our old office no longer exists; the building which housed it now stands vacant.
Travis finished his master’s, moved to Ottawa, and is now happily married.
Even our blog has had three homes since inception (at www.obesitypanacea.com, at ScienceBlogs, and now on PLoS blogs).
Our long-time readers may also remember that back in April of 2010, I defended my PhD. A couple of weeks later, my partner, Marina, also defended hers.
Since my defense I have been a bit more absent on the blog, leaving Travis to do much of the heavy lifting in terms of content (Thank you buddy!) As some of you have been wondering what I have been up during this time, I’ll briefly explain.
You see, near the end of our respective degrees, some 10 years deep into post-secondary education, Marina and I had realized that we had allowed our work to overshadow our lives. We had let hobbies, friendships, and even our relationship become secondary in importance to filling our respective CVs with more publications, presentations and other tokens of academic success.
Thus, around the time we were finishing up our theses, we made a pact to remedy this imbalance.
Not surprisingly, within 3 days of Marina’s defense, the two of us were on a one-way flight to Ecuador.
For the first time in our lives we didn’t have the next step planned out.
And it was exhilarating.
Not to mention frightening.
Since then, we haven’t really stopped moving. Over the past year and a half, Marina and I have lived in four cities in 3 different countries, have traveled to over a dozen other countries, and have finally checked off a few items off of our bucket lists.
I’m actually writing these words from our current temporary home in Auckland, New Zealand.
When we first set off for South America, I hastily started a blog to document our travels and named it PhD Nomads.
At the time I had no idea how accurate this moniker would soon become.
Nevertheless, here we are, as our tagline suggests: “an over-educated couple on an extended ‘workation’.”
If I haven’t bored you yet, and you’d like to learn all the juicy details behind our currently nomadic lifestyle, please click here.
Also, if you would like to follow our adventure you can sign up for updates via email or RSS reader – just as you do with Obesity Panacea.
Finally, if you have any questions pertaining to any of the travel we have done, please feel free to contact me.
In the meantime, as we temporarily reside in New Zealand, I’ll do my best to write about our adventures in Southeast Asia over the past 4 months, as well as provide new content for Obesity Panacea.
Image created using photos from goldberg and Bengt Neyman (Flickr)
I recently came across a very interesting study published in Circulation in 2001. In it, authors Darren McGuire and colleagues perform the 30-year follow-up on a group of 5 men who had taken part in the Dallas Bed Rest and Training Study (DBRTS). The DBRTS took place in 1966, when all 5 men were healthy 20 year-olds. They were assessed extensively at baseline, following 3 weeks months of bed rest, and following 8 weeks of physical training. In 1996 these same 5 men were re-assessed, allowing the researchers to compare the influence of 3 weeks of bed rest and 30 years of aging on markers of fitness.
As you’d expect, there was a significant increase in both body weight and body fat percentage over the 30 year period. But what I find more interesting is what happened to aerobic fitness. Below are the results of the VO2 max tests at baseline, post bed rest, and after 30 years of aging (error bars represent standard deviation)
It looks as though 3 weeks of bed rest resulted in a substantial reduction in fitness in the group as a whole, a reduction which was even larger than the one seen after 30 years of aging. Given that there are only 5 participants, it is not surprising that the above changes were not statistically significant. But when you look at the values for each individual participant (below), the results are even more striking.
The above figure would seem to suggest that 3 weeks of bed rest resulted in a consistent and rather substantial reduction in aerobic fitness in all 5 participants, while the impact of aging seems less consistent. Again, there is no statistical significance, but it’s an interesting figure nonetheless.
Even moreso than with most papers, this study has a number of obvious limitations. There were only 5 participants, the above results weren’t statistically significant, and the results were not controlled for other important factors. So why post it here? Frankly, because it’s kinda neat! I love studies with rigorous design, but opportunistic studies like this can go a long way to filling in gaps in the narrative where more rigorous studies end off. Not to mention that this was one of the first papers to suggest that sedentary time could have a strong influence on health. Interestingly, the authors conclude that it is the lack of physical activity – as opposed to sedentary behaviour – which resulted in the apparent reduction in fitness following 3 weeks of bed rest. Personally, I’m inclined to think that sedentary behaviour itself may have an independent impact on health, as I’ve discussed previously, but that’s a discussion for another day.
I know I’m reading more into this than the data itself might suggest. So what do you think – is bed rest likely to be as bad or worse for fitness as 30 years of aging, or is this nothing more than over-interpretation of a null result? I’d love to hear your thoughts.
Travis
McGuire DK, Levine BD, Williamson JW, Snell PG, Blomqvist CG, Saltin B, & Mitchell JH (2001). A 30-year follow-up of the Dallas Bedrest and Training Study: I. Effect of age on the cardiovascular response to exercise. Circulation, 104 (12), 1350-7 PMID: 11560849
Travis Saunders is a PhD student researching the relationship between sedentary time and chronic disease risk in children and youth. He is also a Certified Exercise Physiologist and competitive distance runner. You can connect with Travis on Twitter.
Peter Janiszewski has a PhD in clinical exercise physiology. He's a medical writer/editor, a published obesity researcher, university lecturer, and an advocate of new media in scientific knowledge translation. You can connect with Peter on Twitter. For more information please visit his website.
About Obesity Panacea
The opinions expressed here belong only to Peter and Travis and do not reflect the views of any organization. Any medical discussion on this page is intended to be of a general nature only. This page is not designed to give specific medical advice. If you have a medical problem you should consult your own physician for advice specific to your own situation.
If you go to your physician’s office and inquire about your weight status, he or she will measure your height and weight to derive your BMI (weight in kg divided by height in m squared). Then they will compare your BMI to that of established criteria to decide whether you are underweight (<18.5 kg/m2), normal weight (18.5-24.9 kg/m2), overweight (25-29.9 kg/m2), or obese (>30 kg/m2) . Often times, this measure alone determines whether or not you receive lifestyle treatment.
