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Archive for January, 2011

Sweat Science, the book: coming on May 24

January 30th, 2011

Some exciting news to announce: the book I’ve been working on for the past three years, on the science of fitness, exercise and performance, will arrive in stores on May 24 of this year! The title is Which Comes First, Cardio or Weights? Fitness Myths, Training Truths, and Other Surprising Discoveries from the Science of Exercise. Yeah, it’s a mouthful…

It’ll be published in Canada (pre-order from Amazon here) by McClelland & Stewart, and in the U.S. (pre-order from Amazon here) by HarperCollins. Japanese and Korean editions are in the works, and hopefully other international editions will follow. Note that if you click on the Canadian links, they still have old title listed, which was “Sweat Science” instead of “Which Comes First, Cardio or Weights?” It’s the same book — the marketing people determined that having a question in the title would cunningly lure people into picking up the book in search of an answer.

Anyway, there will be lots more about the book in the months to come — plus details about promotions, speaking engagements, and even some giveaways! — but for starters I just wanted to get everyone to mark May 24 in the calendar. :)

Heart health, exercise, and misleading correlations

January 28th, 2011

Just noticed a great post on Amby Burfoot’s Peak Performance blog where he interviews Paul Thompson, the Hartford Hospital cardiologist who’s the go-to guy for questions about exercise and heart health. It’s a fantastic interview, very wide-ranging, with Thompson sharing his thoughts, hunches and beliefs about a bunch of the current controversies in this area.

One part that caught my attention in particular was a question about a recent German study that found a high prevalence of hardened arteries among marathon runners (I blogged about it here). Thompson was a co-author on the study, and he shared a frank assessment of some of the study’s strengths and weaknesses:

[H]is marathon group includes a number of former smokers and others who might have been quite unhealthy before they began running…

The key issue with Mohlenkamp’s runners is that their cardiac risk scores are compared using their present cholesterol, blood pressure, and other health numbers. They might have had terrible numbers before they started running, so when their coronary calcium is compared with folks who are not athletes, but had good risk numbers all their lives, it looks like the runners had more calcium, ie, more atherosclerosis than predicted by their risk factors… Many of the runners “got religion” when they turned 40 or so.

This is a classic illustration of why a single study, or even a single group of studies, can so easily point us in the wrong direction. On the surface, it looks simple: take a bunch of marathoners, compare them to controls, and presto — marathoners have worse arteries. But it’s easy to be led astray by underlying factors (not to mention, as Thompson points out, that the hard, stable arterial plaques found in the runners may actually be a good thing, as opposed to soft, unstable plaques that are easily dislodged).

Anyway, it’s an interesting read, and Burfoot does a great job “pinning Thompson to the mat” to get his (well-informed) opinions and best guesses on a bunch of topics.

Does skipping breakfast make you fat or thin?

January 28th, 2011

I should state my bias up front: I’m a big believer in the importance of breakfast, fully indoctrinated by my mother from a very young age. So when I saw this press release, my skepticism ramped up to full power. It describes a new study in Nutrition Journal (full text available here) that analyzed the diets of 280 obese and 100 normal weight subjects for 10 to 14 days, concluding that eater a bigger breakfast led to greater overall caloric intake for the day:

Therefore, overweight and obese subjects should consider the reduction of breakfast calories as a simple option to improve their daily energy balance.

Heresy! Or is it… I decided I should at least read the paper. It turns out this is, indeed, a long-running debate. The authors of the new study, from the Else-Kröner-Fresenius Center of Nutritional Medicine (in Munich, where compound nouns are a way of life), argue that previous studies have been guilty of what seems like a fairly obvious error in interpretation. These previous studies have found that the higher the proportion of your daily calories you get at breakfast, the lower your overall caloric intake is that day. But these results are skewed by days when people choose to have unusually small lunches and dinners, the new study argues.

The details of this statistical debate are fairly intricate — and not that interesting, actually. Because the strongest arguments for breakfast were never predicated on the theory that you’d eat less later. It’s the other side of the energy balance equation that’s more interesting. By taking in the calories at the start of the day, you’re getting them right when you need them, rather than later when your physical activity for the day is done. You’re also getting your body out of starvation mode so that you’ll choose healthier foods and not store everything as fat when you finally cave in and have some food.

So what are the long-term effects of skipping (or not skipping) breakfast? A study in December’s American Journal of Clinical Nutrition followed 2,184 Australian kids back in 1985, and then checked in again in 2004-2006. The study looked for the effects of skipping breakfast as a kid, an adult, both, or neither. The results:

[P]articipants who skipped breakfast in both childhood and adulthood had a larger waist circumference and higher fasting insulin, total cholesterol, and LDL cholesterol concentrations than did those who ate breakfast at both time points.

Now, you might say that the people who skipped breakfast also happened to be Very Bad People in other aspects of their health. That’s a fair point — though the researchers do at least try to account for the possibility that the breakfast-skippers were eating trash for the rest of the day:

Additional adjustments for diet quality and waist circumference attenuated the associations with cardiometabolic variables, but the differences remained significant.

If you’re still not convinced, consider this final salvo, from the European Journal of Clinical Nutrition in September. Researchers at King’s College London analyzed the breakfasts eaten by 60 kids, then gave them a battery of cognitive tests. Now, it’s old news that breakfast makes you smarter. The new wrinkle in this study is that they broke the data down into four groups depending on glycemic index (how quickly sugars will enter the bloodstream) and glycemic load (glycemic index times portion size). The results weren’t entirely straightforward, but the best option seemed to be a low-GI, high-GL breakfast — in others words, have a big breakfast but make sure it’s not just a bunch of sugar and refined cereal or bread.

Last point: this isn’t carte blanche to totally ravage the breakfast buffet. In the study that sparked this post, one of the foods that contributed most to breakfast calories was cake (51 cal for the obese group, 132 cal for the normal group!). I mean, come on! If the Else-Kröner-Fresenius folks are advocating skipping breakfast to lose weight, then I heartily disagree. But if they’re just suggesting that you should go easy on the cake and sausages, then yeah, that sounds like pretty good advice — at any meal.

Turn down the thermostat to battle the obesity epidemic

January 27th, 2011

Here’s one I hadn’t heard before:

Increases in winter indoor temperatures in the United Kingdom, United States and other developed countries may be contributing to rises in obesity in those populations, according to [University College London] research published today.

The claim comes from a new paper in Obesity Reviews (press release here), and on the surface, at least, seems plausible.

Reduced exposure to cold may have two effects on the ability to maintain a healthy weight: minimizing the need for energy expenditure to stay warm and reducing the body’s capacity to produce heat.

In particular, the authors note, exposure to cold is thought to stimulate the production of the famous but elusive “brown fat” that burns calories to generate heat. The paper itself goes into great depth about the proposed mechanisms and the expected effect size. Two graphs that I found interesting; first, indoor temperature trends in the U.S. and U.K.:

indoortempI love that U.K. bedroom temperature data! I lived in an unbelievably leaky apartment in Montreal for a couple of years — it was the former “coach house” behind a grander building, so it had no insulation. We were paying for our own heat, and had no money, so we kept the thermostat in the living room down about 13-15 C, and didn’t bother heating the bedrooms, kitchen or bathroom. We kept a “guest blanket” on the couch for anyone foolish enough to visit. And both my roommate and I were pretty skinny throughout those two years…

tempvsenergy

This is the crucial data — 24-hour energy expenditure as a function of temperature. Could it make a difference? Maybe. But before anyone gets too upset about this, I should note that even the authors of the paper aren’t proposing that this is the cause of obesity — they’re just suggesting it could be one of the many contributing factors.

Carb needs for different exercise durations

January 24th, 2011

Today’s Globe column brings together a few recent topics of discussion from the blog about carbohydrate needs for short, medium and long exercise bouts:

The question

How long can I go before I need to “refuel” with carbs, and how much do I really need?

The answer

If you’re spending nine hours doing an Ironman triathlon, you definitely need fuel. Samantha McGlone, the 2007 World Championship silver medalist, downs five sports drinks during the bike ride, and adds one or two energy gels an hour to her drinks during the run.

“But I have done Olympic-distance races [which take about two hours] on water,” says the Montreal native, who represented Canada in triathlon at the 2004 Olympics. “Maybe not the best, but back in the day …”

Researchers have been arguing for years about whether carbohydrates make any difference during exercise lasting an hour or two and, if so, how much you need. Recent experiments suggest that during shorter workouts, carbs are for the brain rather than the muscles, and that during longer workouts, not all carbs are created equal… [READ THE WHOLE ARTICLE]

Also worth checking out is Trish McAlaster’s nice graphic that accompanied the article, based on information provided by Asker Jeukendrup:

carb-needs

How many carbs can a super-carb-absorber absorb during a triathlon?

January 22nd, 2011

Following up on my post on maximizing carbohydrate absorption during exercise a few months ago, I got an interesting e-mail from a triathlete named Josh (yeah, I’m still way behind in catching up on e-mail since the trip to Nepal!). His question was basically: Forget about averages, how high can an individual outlier push his or her rate of carb absorption, with training and good genetics?

I’m a tall and lean guy and at Ironman this past year I ate 600 calories [150 g] per hour for 5 hours on the bike and ate at around 450 cal [~112 g]/hour on the run. That’s well in excess of ANY average rate that anyone has ever suggested is “possible on average”…

It’s an interesting question. After all, as Josh pointed out, the average marathon time is around four hours, but we don’t focus our training discussions on how to be average. So I dug up Asker Jeukendrup’s recent review of multiple transportable carbs to see if it would shed any light.

The first key point, of course, is the difference between ingestion and absorption. While Josh was ingesting 150 g an hour, that doesn’t mean all those carbs were reaching his muscles — they could be hanging around in his stomach, or passing through his intestine without being absorbed into the bloodstream, destined for an eventual rear exit. A very nice table in Jeukendrup’s paper sums of the results of 13 studies: Read more…

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Known knowns, unknown unknowns and the limits of science

January 22nd, 2011

Every once in a while, I’m contacted by product reps who offer to send me the latest high-tech sports gear to try out and review on the site. While I sincerely appreciate their offers, I decided when I started the site that I wouldn’t do first-person reviews. That’s partly so that readers can assume that when I do criticize or compliment a product, it’s an unbiased opinion. But it’s also because I really don’t place much value on n=1 experiments. (If I try a pair of compression tights, I can obviously judge whether they’re comfortable and come in pretty colours, but it’s impossible for me to tell in any meaningful way whether they made me faster or less sore. Or more precisely, if I run faster and feel less sore, it’s impossible for me know what really caused it.)

This question of what constitutes meaningful evidence is a constant undercurrent on this blog, and it occasionally pops to the surface. For example, I’ve been arguing about the fundamental mechanisms of weight loss for most of this week — and I think I generally agree with the guy I’m arguing with, we just differ on the extent to which the science is settled. Or, for a different take on the nature of evidence, here’s a few lines from a comment that popped up yesterday on an old post about “cryotherapy”:

[Y]ou see people getting in and out of them constantly… like a revolving door! Why would people put themselves in such cold temperatures if it doesnt help them with something?? I only went in once so I dont know if I reaped any long term benifits but I loved the way I felt after I got out! I couldnt stop giggling and I didnt know why! [...] I hope you stubborn North Americans learn to see past your ignorance to the rest of the world and try something before you knock it

All of this is on my mind these days because of a few very interesting recent articles on the systematic problems inherent in the medical literature. (And let’s not kid ourselves, the sports science literature has a long way to go before it reaches even that level of unreliability!) So on that note, some suggested weekend reading:

If I could summarize the articles in a few lines, I would. But they’re not simple — particularly Lehrer’s article, which covers some pretty broad territory beyond the obvious problems of publication bias, study design, bad statistics, and so on. If it’s a topic that interests you at all, they’re both worth a read.

Finally, for a slightly more practical (and optimistic) take on how these somewhat abstract concerns intersect with real life, read Steve Magness’s post on “Science Vs. Practice: Should our training be evidence based?

(Thanks to Amby B., Ian R. and Amy M. for pointing these articles out to me.)

Why I like Gary Taubes but don’t believe he’s the Messiah

January 18th, 2011

Weight loss is a pretty controversial topic, so I always expect to take some flack when I write about it, from people who are convinced they know “the truth.” (The fact that I hear from so many different people with so many different versions of “the truth” is a good reminder that it’s impossible to make everyone happy.)

I certainly don’t know the full truth about weight loss, but I did my best in Monday’s Globe article to summarize my understanding of the current literature. The most common complaint I’ve heard so far relates to my treatment of Gary Taubes’s ideas. Early in the piece, I referred to his latest book as an “anti-carb polemic.” Later in the piece, I wrote “Mr. Taubes’ core idea, that refined carbs cause a damaging spike of glucose that can affect insulin function (and thus fat storage) is backed by quite a bit of science.” To me, that seems like a fairly even-handed treatment — if anything, I’m coming down on his side. Nonetheless, I’ve heard from several people who say I’ve careless misinterpreted or misunderstood Taubes’s point.

For the record, I think Taubes’s critiques of existing nutritional orthodoxy are enormously important, and I made significant changes to my diet after reading Good Calories, Bad Calories. However, I also think he does exactly what he accuses his opponents of: drawing conclusions from epidemiological and mechanistic studies without confirmation from intervention trials. Or to put it another way, just because everyone else is wrong doesn’t mean Taubes is right and his orthodoxy can’t be questioned.

I had a very long and very interesting interview with Taubes a few years ago. In case anyone’s interested, here’s a transcript of one of the last questions I asked him. This question — and his response — is one of the reasons I don’t believe he has the “final solution” to understanding weight loss, diet and health.

AH: The last thing that I was trying to reconcile is the role of exercise. If you were to take a sample of 100 serious marathon runners, you’d have a fairly emaciated group who, traditionally, have been instructed to eat as many carbs as they can. Read more…

The science of weight loss

January 17th, 2011

I have a fairly lengthy article in today’s Globe and Mail on the science of weight loss. My assignment was basically to sum up what works, what doesn’t work, and what we still don’t know. Yeah, it was a big topic…

[...] “People want to hear that there are ‘good’ and ‘bad’ foods, and that you simply need to avoid the bad foods and only eat the good foods and you’ll be fine,” says Yoni Freedhoff, the founder of Ottawa’s Bariatric Medical Clinic and one of Canada’s foremost obesity clinicians [and author of the excellent Weighty Matters blog].

Over the past few decades, we’ve tried cutting carbs, eliminating fat – or meticulously optimizing the ratio between them; we’ve eliminated meat and subsisted on liquids; we’ve even eaten according to our blood type. The result? When Statistics Canada went out and actually measured thousands of Canadians (instead of trusting them to tell the truth about their weight) between 2007 and 2009, they found that 61 per cent of us were overweight.

As we begin a new decade, obesity researchers are turning away from this search for “good” foods – a quest that has led us down a nutritional rabbit hole, in which the rich complexities of the human diet are reduced to didactic edicts that change every few years.

Instead, they’re focusing more on the physiology and psychology of why people eat what they do, how societal forces influence their choices, and what they can do to change. The code hasn’t been cracked yet, but here’s what we do know about weight loss. [...]

More evidence that sitting too much is bad even if you exercise

January 16th, 2011

One of the most surprising bits of research to emerge last year was the finding that too much sitting can be very bad your health, no matter how much exercise you do. In other words, going to the gym every day can’t undo the damage done by sitting in front of a computer all day then laying on the couch all evening.

The trickle of research that started last year is now becoming a flood — for example, I noticed two more studies released in the last few days. One, in the American Journal of Cardiology, reported the following:

Data show that compared to people who spend less than two hours each day on screen-based entertainment like watching TV, using the computer or playing video games, those who devote more than four hours to these activities are more than twice as likely to have a major cardiac event that involves hospitalization, death or both.

The other, in the European Heart Journal, puts a more positive spin on how to mitigate the risks of prolonged sitting:

“Our research showed that even small changes, which could be as little as standing up for one minute, might help to lower this health risk. It is likely that regular breaks in prolonged sitting time could be readily incorporated into the working environment without any detrimental impact on productivity, although this still needs to be determined by further research…”

This whole topic is still a little bewildering for those of us who’ve grown up thinking that getting enough daily exercise means you’re not “sedentary.” Fortunately, just last week Travis Saunders of Obesity Panacea did a nice job of explaining what’s currently known about the science in this area in a guest post at Scientific American. For example:

But what I find truly fascinating is that sedentary behavior also results in rapid and dramatic changes in skeletal muscle. For example, in rat models, it has been shown that just 1 day of complete rest results in dramatic reductions in muscle triglyceride uptake, as well as reductions in HDL cholesterol (the good cholesterol). And in healthy human subjects, just 5 days of bed rest has been shown to result in increased plasma triglycerides and LDL cholesterol, as well as increased insulin resistance—all very bad things. And these weren’t small changes—triglyceride levels increased by 35%, and insulin resistance by 50%!

[...] What is most interesting to me personally is that these physiological changes in skeletal muscle have little or nothing to do with the accumulation of body fat, and occur under extremely rapid time-frames. This means that both lean and obese individuals, and even those with otherwise active lifestyles, are at increased health risk when they spend excessive amounts of time sitting down.

Travis’s whole post is definitely worth a read, as its puts the whole body of research into context (and there are some good questions and answers in the comments section).