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

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As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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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: Continue reading “How many carbs can a super-carb-absorber absorb during a triathlon?”

Known knowns, unknown unknowns and the limits of science

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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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

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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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. Continue reading “Why I like Gary Taubes but don’t believe he’s the Messiah”

The science of weight loss

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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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

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

***

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).