Is strength training really better than cardio for weight loss?

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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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I did a radio interview today with Angela Kokott on QR77 in Calgary, and one of the questions we discussed was the perennial claim that lifting weights is better than aerobic exercise for burning calories. It’s a claim that isn’t totally crazy — even the most recent American College of Sports Medicine position stand on weight loss reverses earlier stands by acknowledging the possibility that resistance training could contribute to weight loss by elevating resting metabolic rate, increasing fat oxidation, and making people more active generally. Here’s the funky flowchart they use to illustrate this process:

Still, the “evidence statement” endorsed by the position stand is: “Resistance training will not promote clinically significant weight loss.” In other words, it’s a nice theory, but the studies of actual people losing weight don’t back it up.

The reason I bring this up is that James Fell has a good article in the Los Angeles Times that tackles this topic — in particular, taking on the oft-repeated whopper that every pound of muscle burns an extra 50 calories a day. He turns to Claude Bouchard of Pennington Biomedical Research Center, who offers the following breakdown of resting metabolic rate (RMR):

Brain function makes up close to 20% of RMR. Next is the heart, which is beating all the time and accounts for another 15-20%. The liver, which also functions at rest, contributes another 15-20%. Then you have the kidneys and lungs and other tissues, so what remains is muscle, contributing only 20-25% of total resting metabolism.

The punchline, according to Bouchard: a pound of muscle burns about six calories a day while a pound of fat burns two calories a day. Don’t get me wrong: strength training is great for many reasons, and I certainly encourage everyone (including, reluctantly, myself) to do some. But it’s not a miracle weight-loss technique.

Does fat matter?

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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Just a decade ago, our concept of “healthy eating” was so simple and straightforward: fat is bad. These days, not so much. Amby Burfoot’s most recent Peak Performance blog post summarizes the key points from “The Great Fat Debate” held among four highly respected nutrition experts (Walter Willett, Alice Lichtenstein, Lewis Kuller, and Darius Mozaffarian) in the current issue of the Journal of the American Dietetic Association.

There was plenty of disagreement, but some common ground. For example, total fat is less important than the type of fat: saturated fats (e.g. dairy and meat) are less desirable than unsaturated fats (e.g. olive oil). But replacing fats with processed carbs isn’t the answer, and will probably make things worse — which brings up the fundamental problem with this kind of debate. As Harvard’s Mozaffarian puts it:

Dietary recommendations that focus on selected nutrients, such as total fat or saturated fat, are often confusing for the public, result in illogical dietary decisions, and increase the potential for manipulation of nutrient targets by the food industry… If we’re eating an otherwise healthful diet including plenty of vegetable oils, fruits, vegetables, fish, and nuts, it will be much less important what the saturated fat level is.

Or as Lichtenstein (of Tufts) puts it, more simply:

I think we have to stop talking about individual dietary components because when one goes up another goes down.

Given the continuing disagreement about fundamental questions (is cholesterol bad?), it seems pretty clear to me that we don’t have enough understanding of the complex relationship between diet and health to successfully micromanage the ratios of specific nutrients. On the other hand, we have pretty unambiguous evidence about the benefits of certain patterns of eating — like getting lots of vegetables and fruit. Until the research is a little less murky, that’s the approach I’m sticking with.

Arthur Lydiard recording

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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Bit of an obscure find for distance running fans out there: a three-hour recording of a speech by Arthur Lydiard in 1963 at San Jose State University, with Peter Snell and Murray Halberg throwing in their two cents and answering questions. This was three years after Snell, Halberg and marathoner Barry Magee took gold at the Rome Olympics, and the year before Snell took double gold in Tokyo. It’s on sale at BudWinter.com — Winter was the coach at San Jose State from 1941 to 1970, and he’s the one who hosted the talk and introduces Lydiard.

I’d never actually heard Lydiard speaking; it’s pretty funny in places. For example, Peter Snell’s first 22-mile run with the group:

[With 2.5 miles to go], he started crying like a kid, tears running down his face. And no one would help him. We said, ‘Look, you’ve only got a little way to go, just keep plodding’… He lay on the bed and he sobbed for half an hour like a kid. Now we’re not very sympathetic. We said, ‘Look, Snell, in two weeks’ time you’re going around there again.’

And his thoughts on stretching and other conditioning drills:

I don’t think Halberg or Snell or any of those guys could touch their toes. I honestly don’t. It’s not because I don’t believe in exercises, loosening and stretching. It’s solely because we haven’t got time to do it. And I don’t think it would make them run any faster anyway.

Anyway, a fun little piece of history for any Lydiard fans out there!

Cycling in the heat: knowing the temperature slows you down

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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You run or bike slower in hot conditions because your body overheats… right? Actually, it’s a bit more complicated than that, according to a neat study from the University of Bedfordshire and the University of Brighton posted online at the European Journal of Applied Physiology a couple of days ago.

Here’s what they did: seven cyclists performed three 30-minute time trials under different conditions:

  1. the control trial, at 21.8 C
  2. the hot trial, at 31.4 C
  3. the “deception” trial, at 31.6 C — but thermometers were “fixed” so that the room temperature was displayed as 26.0 C, and the rectal temperatures of the cyclists were displayed as 0.3 C lower than they really were.

As expected, the cyclists covered ~4% less distance in the hot trial than the control trial. But in the deception trial, the heat didn’t hurt them at all — they covered just as much distance (slightly more, actually) than in the control trial!

This study joins a long-running dispute about exercise in the heat, sparked by work from Ross Tucker and others in Tim Noakes’s group in Cape Town. What Tucker argues is that we don’t slow down because we’re dangerously hot; we slow down to avoid getting dangerously hot: the “central governor” in our brains forces us to slow down before we reach any critical temperature. That’s why, if you do a 30-minute cycling time trial in hot conditions, you’ll already be behind your “normal temperature” pace within the first five minutes, and your brain will be recruiting fewer muscle fibres — even though, at that early stage in the trial, your core temperature is still relatively low.

Tucker argued that this is all unconscious, and your brain monitors the rate of heat storage in your body. Others like Samuele Marcora at Bangor argue that it’s a conscious process dictated by your feelings of discomfort. The authors of the new study view their results as supporting the central governor model, but there are a few interesting wrinkles. In particular, the measured skin temperature of the participants was ~0.5 C lower in the deception trial than in the heat trial for the first 15 minutes. This is a real physical effect, not just “in the head,” which the authors explain as follows:

We speculatively propose that the perceived need for heat dissipation was less during the early stage of the TT in DEC, which caused an involuntary autonomic reflex to reduce peripheral blood flow, resulting in lower [skin temperature]…It appears that a response based on incorrect conscious information may be sufficient to produce a subconscious physiological effect that resulted in an improved performance.

Strange stuff. So any practical benefits? It’s hard to imagine convincing your coach or spouse to give you fake weather reports on race days (or at least, it’s hard to imagine falling for it more than once). On the other hand, this suggests that your beliefs about how weather affects you can actually become self-fulfilling prophecies. If you’re convinced that heat will slow you down, it will. On the other hand, maybe someone like Sammy Wanjiru (RIP) simply wasn’t burdened by the belief that heat would slow him down — which could help explain his otherwordly performance in the heat of the Beijing Olympic marathon.

Training in a carb-depleted state: pros and cons

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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This week’s Jockology column in the Globe and Mail takes a look at some of the benefits and risks of working out in a carbohydrate-depleted state:

For decades, sports nutritionists have been devising ever more sophisticated ways to ensure your body is perfectly fuelled before, during and after every workout. With gels, bars and belt-mounted drink bottles, you can have calories within reach no matter where you are.

But what if quaffing fewer carbs and calories – or even none – resulted in a better workout?

At a recent sports nutrition conference at the Australian Institute of Sport in Canberra, researchers and coaches were buzzing about an emerging practice they refer to as “train low, compete high.” The idea is to do some of your workouts in a carbohydrate-depleted state – the nutritional equivalent of training while wearing a weighted vest – then race with a full tank of carbohydrates.

With initial research showing the technique boosts fat-burning, as well as other metabolic responses to exercise, elite athletes aren’t the only ones taking note. It remains a controversial approach – but it’s relatively easy to give it a try… [READ ON]

For more on this topic, including the idea that low-carb training might be suitable during base training but not other times of year, check out this blog entry from last month.