Author: alex

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Does a rapid metabolism make you die earlier?

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My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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In many ways (particularly around dessert time), having a rapid metabolism is a blessing. But is there a downside? No one really believes that we have a “set number of heartbeats,” and we die when we use them up. On the other hand, it seems reasonable to view aging as the consequence of a series of cellular events, and “metabolism” as basically a measure of how fast those (and other) cellular events are proceeding in your body. That would certainly fit with all the research about caloric restriction extending lifespan. But frankly, it would kind of suck to think that boosting your metabolism was going to rob you of a few of your twilight years.

A new study in the Journal of Clinical Endocrinology & Metabolism looks into this question; the study will be published in June, and unfortunately I don’t have access to the advance online version, so the only details I have come from this press release. The researchers looked at 652 healthy Pima Indian volunteers between 1982 and 2006, measuring their resting metabolic rate and/or 24-hour energy expenditure (using a metabolic chamber). During the study, 27 of the participants died, and higher metabolism was one of the risk factors:

“We found that higher endogenous metabolic rate, that is how much energy the body uses for normal body functions, is a risk factor for earlier mortality,” said Reiner Jumpertz, MD, of the National Institute of Diabetes and Digestive and Kidney Diseases in Phoenix, Ariz., and lead author of the study. “This increased metabolic rate may lead to earlier organ damage (in effect accelerated aging) possibly by accumulation of toxic substances produced with the increase in energy turnover.”

“It is important to note that these data do not apply to exercise-related energy expenditure,” added Jumpertz. “This activity clearly has beneficial effects on human health.”

So that last part is reassuring, though I’m not sure on what basis he makes the claim. (Isn’t it possible that exercise-related energy expenditure produces the same negative effects as “endogenous” energy expenditure, but the downsides are more than compensated for by other benefits provided by exercise?) And he only seems to be referring to energy burned during exercise. But what about changes in basal metabolism induced by regular exercise? I’m under the impression (though I’m just assuming here, and happy to be corrected) that regular exercise does boost your metabolism throughout the rest of the day. Is that a problem?

Anyway, nothing to get too worked up about here: it’s clear from epidemiological data that the net effect of exercise is to increase rather than decrease lifespan. Still, I’ll be curious to see the full study when it’s published, to get a fuller sense of the research in this area than the press release provides.

[As an aside, I’m now back in Toronto after a week of travelling from Sydney to San Francisco to Vancouver, so the blog should get back to full throttle after last week’s lull! Many thanks to all those who dropped by Forerunners and the Vancouver Marathon expo to say hello and pick up advance copies of the book — and sorry I ran out so quickly!]

UPDATE May 2: A friend sent me a pdf of the full paper (thanks, Joe!), so I now have a fuller sense of the argument. The authors are interpreting their results in terms of the “free radical theory of aging” (though they acknowledge that some recent experiments have cast doubt on this theory). In this theory, it’s clear that a chronic elevation of free radicals due to excess food consumption (i.e. a faster basal metabolism) is bad, while a transient spike in free radicals due to exercise (which in turn spurs the body to adapt by developing a more powerful antioxidant response) is good rather than bad. One other point: the average BMI of the volunteers was ~34, and many of the deaths were linked to alcohol. So overall, I’m not necessarily confident that the primary result (faster metabolism = earlier death) is really generalizable to, say, a group of committed runners.

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Sports fans and their heroes in the wired age

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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A quick plug for an essay of mine that appeared in Maisonneuve a few months ago (the full text has just been made freely available online), about the changing relationship between sports fans and athletes in the wired age. It’s a long piece that mixes some personal history with sociology and (inevitably, as a runner!) some discussion of the Letsrun message boards:

A CBC video clip of the 1996 Canadian Olympic Track and Field Trials recently surfaced online. You can watch, in grainy low definition, the twelve finalists in the men’s 1,500 metres step to the line under starter’s orders. A momentary pause, as the runners crouch in anticipation—then the gun fires. Eleven runners explode down the track. The twelfth, inexplicably, stays frozen on the starting line for a brief instant, then snaps out of it and takes off after his competitors. He never quite catches up, and finishes last.

A surprising number of people have stumbled on this clip and emailed it to me, along with some variation of the question, “What the hell happened there?”… [READ ON]

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More on Taubes, Lustig and toxic sugar

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My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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A quick post with a couple of links for those interested in reading more about the Taubes/Lustig “toxic sugar” debate. To hear more from Taubes, check out his answers to numerous reader questions at the NYT site. And to read David Katz’s response to Taubes/Lustig (hat tip to Yoni Freedhoff at Weighty Matters), click here. A peek at Katz’s conclusion:

As dietary guidance, the vilification of one nutrient at a time has proven as flighty as hummingbirds, propelling us from one version of humbug to another. My advice is to grasp firmly your common sense, and stay grounded.

The hummingbird stuff makes more sense if you read the whole post, but it’s generally a Pollan-esque argument rather than a research-y one. Still, it’s about where I come down. Taubes’s response to that point:

This is a common argument over the years, that reductionism in nutrition research misses the point. Michael Pollan makes this argument in “In Defense of Food.” The counter argument is that this is, indeed, a science and one way sciences make progress is by reducing problems down to their basics. This can often be misleading, and Suzanne’s point (as with Michael Pollan’s) that it has been in the past is very true.

I’ve been a strong journalistic opponent of the belief that salt causes hypertension or that dietary fat or saturated fat causes disease and in doing so I’ve attacked the bad science behind some of these reductionist arguments. But just because over the years one single nutrient after another has been singled out as harmful doesn’t mean that one single nutrient isn’t harmful. It only means that the research is poor and some of the beliefs about how research should be done in these fields are also misconceived.

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Does vitamin C block gains from training?

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My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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The traditional theory goes like this: strenuous exercise produces “reactive oxygen species” (ROS), which cause damage to cells and DNA in the body. Taking antioxidant supplements like vitamins C and E helps to neutralize the ROS, allowing the body to recover more quickly from workouts.

The new theory, in contrast, goes like this: strenuous exercise produces ROS, which signal to the body that it needs to adapt to this new training stress by becoming stronger and more efficient. Taking antioxidant supplements neutralizes the ROS, which means the body doesn’t receive the same signals telling it to adapt, so you make smaller gains in strength and endurance from your training.

So which is true? Back in 2009, a German study found that vitamins C and E did indeed block gains in insulin sensitivity — a key adaptation to exercise — in a group of sedentary volunteers. But in January 2010, a study of cyclists found no difference in fitness parameters like maximal oxygen consumption, power output, lactate threshold and so on between a placebo group and a vitamins C/E group. But then last December, a study with rats found that vitamin E did block gains in mitochondria, a key adaptation to endurance training.

Which brings us to the most recent study, published in March in the International Journal of Sports Physiology and Performance. A total of 17 recreational runners did a four-week training program consisting of four interval workouts a week (5x3min hard with 3min jog recovery — a bit of an odd program, but it succeed in significantly boosting VO2max, running economy, 10K time trial performance, etc.). Half the subjects took 1 gram of vitamin C every morning, while the other half took a placebo; the trial was double-blinded, so no one knew who was in which group. The results: no significant differences between the groups.

So where does this leave us? I’m not really sure. The paper discusses a couple of possible explanations. One is that antioxidants do block some training gains but that this study was too small to detect them. With nine subjects in one group and eight in the other, that’s certainly possible. For example, the subjects ran two  “YoYo Intermittent Recovery Tests” with slightly different parameters. In the first one, the vitamin C group improved 22% while the placebo group improved only 16%; in the second one, it was the other way around, with the placebo group improving 10% and the vitamin C group improving only 5%. This doesn’t give me a whole lot of confidence in the test-retest variability, or the ability to detect subtle differences in adaptation.

Another possibility relates to the initial fitness of the subjects. The 2009 German study used sedentary, unfit subjects, who thus would be expected to produce very high levels of ROS in response to the unfamiliar stress of exercise. In these subjects, one might expect antioxidant supplements to make a bigger difference to training adaptations. The new study, on the other hand, used subjects with higher initial aerobic fitness (“recreationally active,” not trained athletes). As the saying goes, “exercise is the most powerful antioxidant we have.” So it’s possible that fit subjects already have reasonably effective natural antioxidant defenses in place, so taking additional antioxidant supplements doesn’t make as much (or any) difference.

All of this leaves us with no firm answer — as usual, more studies are needed. My guess (thinking back to my last post about the pros and cons of training on empty) is that we’ll eventually conclude that the answer is “it depends.” Perhaps antioxidant supplements will be helpful during extremely heavy training blocks, but should be avoided as you approach competition. Or perhaps it’s the other way around: let the ROS run wild during heavy training blocks, but take antioxidants to ensure full repair as competition approaches. The latter approach fits with a Portugese study that found that antioxidants may delay muscle repair after heavy workouts, but could allow muscles to actually work harder in the heat of competition. It’s too soon to know for sure.

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Training without breakfast?

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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Training on “empty” — i.e. with low carbohydrate stores — is one of the hot topics in sports nutrition these days. (I’ve posted on it a few times, for example here and here.) Louise Burke of the Australian Institute of Sport has a good summary of the current thinking in the ACSM’s Sports Medicine Bulletin.

Traditionally, athletes have approached their daily workouts to train as hard as possible, using strategies that promote good performance, just as they would in a race or match. In many sports, these strategies involve fueling up with carbohydrates before, during and between workouts to sustain the capacity to produce power. Recently, however, scientists have proposed an alternative approach…

I won’t bother trying to summarize the whole thing, because Burke is already compressing a lot of information into a small space — if you’re interested in the topic, it’s worth a read. A couple of minor points to highlight, though:

While some publicity surrounding this study suggests otherwise, the outcomes from [training low] weren’t achieved by following a low carbohydrate diet.

This is about having low carb stores for a short period of time, for instance by depleting carbs with a prior workout, not being in a chronically low-carb state. And a very interesting point:

It makes sense that sessions completed at lower intensity or at the beginning of a training cycle are best suited for, or perhaps least disadvantaged by, [train low] strategies. Conversely, quality sessions done at higher intensities or in the transition to peaking for competition might best be undertaken with better fuel support.

In other words, nutrition should be periodized. What you eat — and how you think about the relationship between your food and your performance — should be different in base phase than it is come competition time.