OBESITY PANACEA

One of the most interesting (and most complicated) things about obesity is its very strong neural component.  Now of course at its most basic level, body weight comes down to the balance of energy intake versus energy expenditure.  Unfortunately, many aspects of this energy balance equation are outside the influence of conscious control.  The brain is constantly sensing nutrients like glucose, and hormones like leptin and insulin in order to determine current energy stores, and using this information to adjust energy intake and energy expenditure as needed.  It does this by influencing our hunger and satiety, in order to keep body weight around a chosen set-point, or to return to a set-point after a short-term perturbation (e.g. a crash diet).  So even though an individual may have decided to cut back on their caloric intake and increase their physical activity levels, this is obviously not so easy if their brain is making them feel hungry and lethargic all the time.  As you might expect, research suggests that this neural control of energy intake and energy expenditure plays an extremely important role in obesity, weight maintenance, and weight reduction.

One study that nicely illustrates the link between obesity and these neural mechanisms was performed by Dr C.W. le Roux and colleagues at the Imperial College of London titled "Attenuated Peptite YY Release in Obese Subjects is Associated with Reduced Satiety".  Peptide YY (aka PYY) is a hormone which is secreted from the intestines in response to a meal, and through its effects on the brain has a strong influence on satiety.  The larger a meal, the more PYY that is released and the fuller you feel.  In this study, Dr le Roux and colleagues examined the PYY response in lean and obese individuals. Each subject received 6 different meals throughout the course of the study, varying in both size and caloric density.  They report that for a given caloric load, obese individuals had a dramatically lower PYY response, which was matched by a lower feeling of fullness.  In fact, obese individuals required roughly double the meal calorie content to match the PYY levels in the lean subjects.  However, when the authors injected PYY into the subjects, it produced similar feelings of fullness in both the lean and obese participants.  These results suggest that PYY secretion is lowered in obese individuals, but unlike leptin, central sensitivity to PYY does not appear to be affected.

Unfortunately, the $64,000 question remains - does obesity cause changes in PYY secretion, or does a deficiency in PYY secretion cause obesity?  That question, to my knowledge, has yet to be definitively answered (although I'm going to guess it's a bit of both, which always seems to be a safe bet with this type of thing).  The point, however, is that body weight management is not quite so simple as telling someone to eat less and move more, although those behaviors are still the end goal.  If an individual never feels full, they are obviously going to find it more difficult to lose weight than someone who always feels full.  That's one of the reasons why gastric bypass is so effective - with a smaller stomach, people feel full much sooner!  The more that we know about the neural control of long-term energy balance, the more effective strategies we will be able to develop to help prevent or reduce obesity in the future.

If you find the role of the brain in obesity as interesting as I do, you may be interested in a free presentation by Dr Barry Levin at the University of Ottawa Health Sciences Campus at 1pm on Nov 20.  Dr Levin is an internationally renowned researcher on the area of the brain-obesity connection, and it looks to be a terrific presentation.  It is open to the public, so if you live within driving distance of Ottawa and are interested in obesity research, this event might be for you.  For more info on Dr Levin's presentation, please click here.

Have a great weekend,

Travis

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le Roux, C. (2005). Attenuated Peptide YY Release in Obese Subjects Is Associated with Reduced Satiety Endocrinology, 147 (1), 3-8 DOI: 10.1210/en.2005-0972

International obesity expert Dr Barry Levin will be giving a free lecture at the University of Ottawa Health Sciences campus at 1:00pm on Friday, Nov 20 titled "Strategies for preventing diet-induced obesity".  Dr Levin's work focuses on the role that the brain plays in obesity, and it is expected to be a terrific presentation.  Although the lecture is being hosted by the University of Ottawa chapter of the Canadian Obesity Network Student and New Professionals, it will be open the the public, and I highly recommend that anyone within driving distance of Ottawa consider attending (I'm looking at you, Queen's University!  McGill too!).  For more information you can contact Dr Siham Yasari or myself (I share a lab with the co-chair of the event).

I would also like to congratulate the local chapter of the Canadian Obesity Network Student and New Professionals organization for managing to scrounge up enough money to fly in a world-renowned obesity expert, AND to provide free beverages and snacks for those in attendance (that's right - snacks and beverages!).  This is likely going to be a top-notch presentation, and it is thanks to the hard work of several already over-worked graduate students, as well as the financial support of the University of Ottawa and the Canadian Obesity Network.  Well done to Zach, Angela, and everyone else who has contributed to what promises to be a great event.

Hope to see you on the 20th!

Travis

That's right!

For something a little different, I decided to record and post on Obesity Panacea a lecture I gave this Monday to a 2nd year Physical Activity and Health course at Queen's University. The title of the lecture was: "Physical Activity in the Treatment of Obesity: Beyond Weight Loss."

In the lecture I covered topics such as:

How much weight loss is enough?

Is physical activity without weight loss a failure?

The importance of looking at body composition, cardiovascular fitness, and metabolic risk instead of body weight when assessing the benefit of a physical activity intervention.

And many others...

Enjoy the lecture as posted below in six 10-minute segments. (Reminder to our email subscribers, you must log onto Obesity Panacea to view the videos)













Special thanks to Jenn Tomasone who provided fantastic technical assistance. Also, thanks to the class of KNPE255 for being one of the best classes I have had the pleasure to teach.

Peter

I came across a very cool study last week which was published in the latest issue of the American Journal of Preventive Medicine. In this new paper, Dr Gabrielle Turner-McGrievy and colleagues at the University of North Carolina at Chapel Hill examined the impact of listening to a weight-loss podcast on body weight, physical activity, and fruit and vegetable consumption in overweight men and women. Subjects were randomly allocated to one of two groups; the control group which received a popular and freely available podcast focused on avoiding over-eating, and the experimental group, which received an "enhanced" podcast created by the study authors.  This enhanced podcast was based on Social Cognitive Theory, and included specific information on what to expect when attempting to lose weight, specific goals to achieve, and knowledge about how to achieve these goals.  Both groups received 2 podcasts each week for 12 weeks, and only met face-to-face with the researchers at the baseline and post-testing sessions.

So, what happened?  In comparison to the control group, the group which received the "enhanced" podcast experienced significant increases in their knowledge of weight loss topics, fruit and vegetable consumption, and their level of vigorous physical activity.  Finally, the enhanced group also experienced a 2.9 kg (~6.5 lb) reduction in body weight.

Now I find this study very interesting for several reasons.  First and foremost, it was done in the real world.  This was not a study where the authors strictly controlled the diet and physical activity levels of their participants.  In fact, they purposely minimized contact with their participants!  This is the opposite of many studies, which strictly control the lifestyle of their participants, effectively sequestering them from the day-to-day life.  So while the weight loss and positive lifestyle changes in the experimental group were modest, there is good reason to think that they could persist over the long-term, since they have presumably been incorporated into normal daily life.  And if any type of lifestyle change is to be maintained over the long-term, this is what has to occur.  I also find the idea of podcasting interventions extremely appealing because they are cheap and easy to make as well as to download, making them incredibly accessible.  And finally, in contrast to interventions which provide information in print, people don't need to sit down to listen to a podcast!  I listen to podcasts all the time during my ride to work, during workouts, and when walking to school, and it really is an easy way to take-in information.

Now keep in mind, this study was only 12 weeks long, and the participants in the experimental group only lost about 6.5 lbs.  Also, diet and physical activity measures were obtained through self-questionnaire, rather than being objectively measured, which introduces quite a bit of error.  And finally, the control podcast - which the authors report is a very popular weight-loss podcast - had absolutely no impact on body weight or any other variable of interest. So to answer my own question in the title of this post, podcasts are probably not the cure for obesity.  But evidence-based podcasts like the "enhanced" podcast in the present study may provide a useful tool for people looking to make a positive lifestyle change, and that's definitely a good thing.

A big hat tip to my girlfriend Daun for sending me the link to this study.

Travis

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Turner-McGrievy, G., Campbell, M., Tate, D., Truesdale, K., Bowling, J., & Crosby, L. (2009). Pounds Off Digitally StudyA Randomized Podcasting Weight-Loss Intervention American Journal of Preventive Medicine, 37 (4), 263-269 DOI: 10.1016/j.amepre.2009.06.010

Back in June, I discussed the results of a large epidemiological study in women that showed that women with larger breasts have an increased risk of developing type-2 diabetes.

As soon as Travis and I read this study, we knew we had to do a follow-up study of our own to see if this finding was simply spurious or if there was actually something to large breasts that indicated health risk – beyond that explained by obesity per se.

The project that Travis and I began over a year ago has culminated in both a hot-off-the-press publication in the journal Obesity, as well as my presentation at this year’s Obesity Society meeting in Washington D.C.

In the study, we used body composition data acquired through MRI on about 100 premenopausal women to directly quantify breast size. By using MRI data we significantly improved the methodology used by the authors of the original study on breast size and diabetes risk, who relied on over 20 year recall of cup size as their key measure.

First, we sought to examine if breast tissue volume was associated with any cardiometabolic risk factors, such as glucose tolerance (a known antecedent to type 2 diabetes) and various blood lipids. Since the original authors found an association between cup size and diabetes risk, we expected to find an association between breast volume and cardiometabolic risk factors.

What did we actually find?

Breast volume was not associated with any of the cardiometabolic risk factors measured in any of the statistical models used. However, in these analyses, visceral or intra-abdominal fat was a strong predictor of numerous risk factors – a finding reported in numerous studies.

Next we decided to examine the associations between breast volume and other body fat depots. Here is where the story got interesting. First off, as one would predict, women with larger breasts had more subcutaneous (under the skin) fat in their thighs, abdomen, as well as more visceral and inter-muscular (or ectopic) fat. That is, bigger breasted women tended to carry more fat everywhere.

However, once we controlled for their level of obesity (body mass index and waist circumference) bigger breasted women were no more likely to have more subcutaneous fat in either lower body or abdomen, but were much more likely to have excess fat deposition in the dangerous visceral and inter-muscular depots.

Specifically, our study found that given the same age, body mass index (total obesity), waist circumference (abdominal obesity), women with the highest breast volume had approximately 1.1 and 1.3 kg more visceral fat and intermuscular fat in comparison to women with the smallest breast volume.

In other words, large breasts appear to indicate a phenotype characterized by the augmented deposition of fat in ectopic depots, such as visceral and inter-muscular fat – each of which is independently associated with increased cardiometabolic risk. The extrapolation of our findings suggests that excess visceral or intermuscular fat may be the conduit which explains the previously documented association between breast size and type-2 diabetes.

While our findings are intriguing (someone at the Obesity Society conference suggested I should get an award from the most “unique” study), there exist a couple clinical examples which corroborate our findings.

For example, approximately 40-50% of women undergoing liposuction of subcutaneous adipose tissue from the hips, thighs, or abdomen present with a paradoxical enlargement of breast size of at least one cup as well as a relative increase in visceral fat post-surgery. Additionally, highly active antiretroviral therapy among HIV-positive women is associated with a peripheral loss of functional subcutaneous fat but a compensatory increase in visceral and intermuscular fat (well documented lipodystrophy), in association with a significant enlargement in breast size.

Now before women with large breasts head out to get breast reductions, it is key to consider that our findings are quite preliminary, and furthermore that breast size only appears to be a proxy for other factors which are more likely to be causally related to health risk. Thus, further research in this area is clearly warranted before we begin screening disease risk by breast size. Nevertheless, when explaining our study findings at the conference, I heard many sighs of relief from women who perceived themselves to have smaller breasts.

Have a great Halloween weekend!

Peter

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Janiszewski, P., Saunders, T., & Ross, R. (2009). Breast Volume is an Independent Predictor of Visceral and Ectopic Fat in Premenopausal Women Obesity DOI: 10.1038/oby.2009.336

Not that long ago I discussed how making certain behaviours such as being physically active and eating a healthy diet easier or more fun increases the chances that these behaviours are adopted by most people. For example, the use of cell phone texts to prompt you to park further from the grocery store door or to choose veggies over chips was shown to lead to some weight loss. Also, the video I posted a while back on the Piano Stairs, which has since gone viral, clearly shows that if the healthy choice becomes the easy or more attractive choice, people are more likely to take it.

I just got back from the 2009 annual meeting of the Obesity Society in Washnigton D.C., where I had the great pleasure to meet with many friends and colleagues such as Dr. Yoni Freedhoff of Weighty Matters blog as well as Dr. Arya Sharma of Dr. Sharma’s Obesity Notes blog.

While at the conference hotel, I was once again struck by how difficult it can be to make the healthy choice. For example, I had to ask the concierge where the stairs were so I could walk the 4 flights to my room instead of taking one of the 8 prominently displayed elevators. It turned out the stairwell wasn’t even marked – it was behind an unmarked door in the seating area of one of the cafes. Thus, it was virtually impossible for anyone to be able to take the stairs even if they wanted to (unless they were as oddly persistent as me). Additionally, the hotel restaurant basically had 1 option for breakfast – a buffet including plenty of high fat favourites such as sausages and bacon and lots of sugary cakes, muffins, cupcakes, not to mention “Vitamin D” milk which in fact had the same amount of vitamin D as the fat free variety but contained 70 kcals of fat in one serving (I guess “Fat Milk” doesn’t sound as enticing).

It turns out that the folks who created the Piano Stairs video have also tested their “Fun Theory” in other ways, so I thought I would share 2 more examples of how “fun and easy” leads to behaviour change. Below you will see two neat approaches to get people to throw garbage into a trash bin and to recycle bottles (email subscribers need to log onto Obesity Panacea to view). As I discussed with Dr. Freedhoff (while we waited at the airport for our delayed flights out of DC) – I believe this is the way that we may be able to get people to become more active and eating healthy – by making small but effective changes to their environment. Simply telling people to follow current guidelines for diet or physical activity when our environment is set up to make these behaviours impossible is not only short-sighted but frankly useless.

Enjoy the videos.

Peter

I thought I'd take a quick break from talking about research today to advocate for a new campaign which I think will interest many of our Ontario readers, especially those who are interested in childhood obesity.  The program is called Spark Together for Healthy Kids, and is being coordinated by the Heart and Stroke Foundation of Ontario in the hopes of reducing childhood overweight and obesity, which currently affects 28% of Ontario children.

A background document on the program is available here, which makes a strong case that childhood obesity is a society problem, and requires a societal solution.  Thus, the goal of the campaign is to encourage a public movement in support of a healthier future for Ontario's children, and individuals are encouraged to join the campaign by signing The Spark Promise to our Children, which advocates for healthy, active places for kids to play.  People are also invited to join the Spark Facebook Group where they can connect with other individuals who feel strongly about childhood obesity, physical activity, and nutrition.  To me, the Facebook group is the coolest thing about this initiative, and I would encourage readers from anywhere in the world to check it out by clicking here.  Ending the childhood obesity epidemic is going to require that we come together as a community to advocate for positive changes, and this Facebook page is a great way to connect with like-minded individuals.  I've also got to say that it's nice to see a campaign like this using new media to engage their audience, and I hope that this becomes the norm for other public health initiatives.



Have you been involved with a project that has received a Spark Community Advocacy Grant?  We'd love to hear about your experience in the comments section below.

Travis