Tag: weight loss

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The science of weight loss

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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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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. […]

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Hard work makes food taste better

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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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This is a quirky study, published this week in Proceedings of the Royal Society B by researchers at Johns Hopkins. The basic message is: if you have to work harder to get a certain type of food, you end up finding it tastier than food that you didn’t have to work as hard for. As the press release explains:

[M]ice were trained to respond to two levers. If the mice pressed one lever once, they were rewarded with a sugary treat. Another lever had to be pressed 15 times to deliver a similar snack. Later, when given free access to both tidbits, the rodents clearly preferred “the food that they worked harder for,” [researcher Alexander] Johnson said.

The results held up even when the hard-to-get food was a low-calorie version of the treat. This means, Johnson suggests, that “down the road, obese individuals might be able to alter their eating habits so as to prefer healthier, low calorie food by manipulating the amount of work required to obtain the food.”

That’s a heck of a public health message. Yes, our problem is that healthy food is too easily available, and junk food is too hard to get. To solve the obesity crisis, we need to make potato chips freely available on every corner, while making possession of a carrot a felony offense — that’ll train people to love the taste of carrots!

Okay, okay. It’s a neat (and amusing) study, and it confirms something most of us already knew: food tastes better when you’ve worked up an appetite. Let’s leave it at that, and not pretend we’re going to use this idea to train our taste buds.

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Your neighbourhood affects your BMI — in unexpected ways

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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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Researchers at the University of Alberta just published some interesting data from a six-year longitudinal study looking at links between neighbourhoods, physical activity and body-mass index. Of the people who moved during the study, those who chose new neighbourhoods based in part on walkability maintained their weight (as expected), while those who chose locations based on proximity to outdoor recreation opportunities (surprisingly) gained weight.

This is by no means a perfectly controlled experiement — for example, as the researchers point out, it could be that the subjects choosing to live near outdoor recreation were doing so primarily for their kids. But it certainly fits with other data, like the fact that New York City — highly walkable but terrible for outdoor recreation opportunities —  is among the thinnest cities in the U.S. (42% of people there were overweight, compared to 67% nationally, according to a 2009 study). And it underlines the point that a healthy lifestyle is more dependent on the little things you do on a daily basis, rather than the big excursions you make on weekends.

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High-intensity vs. low intensity exercise for weight loss

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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This week’s Jockology column in the Globe and Mail takes a look at what workout intensity is best for losing weight. Some recent studies suggest that high-intensity exercise can help fight the “efficiency trap” that occurs when you start losing weight and your body tries to revert to your original weight. Other studies suggest that very low intensity physical activity can burn calories without stimulating your appetite hormones. The one suggestion that doesn’t check out is the so-called “fat-burning” zone, according to a recent Australian study in which mice were engineered to burn more fat than carbohydrate. For details, read the full article here.

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Distance running trains the heart, intervals train the muscles

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)

***

“High-intensity interval training” (HIIT) has been receiving lots of research attention recently as a time-efficient way to get in shape. An interesting pre-print has just appeared in Medicine & Science in Sports & Exercise (thanks to Amby Burfoot for noticing it) that adds a couple of interesting wrinkles.

First of all, the study used running rather than the usual stationary biking — so it provides some evidence that the same kinds of protocols that have been extensively studied in cycling also apply to running. Researchers at the University of Western Ontario had 20 (untrained) volunteers perform six weeks of training, three times a week. One group ran steadily at 65% VO2max, starting with 30-minute runs and building up to 60 minutes; the other group did 30-second sprints with four-minute recovery, starting with four repetitions and building up to six.

As expected, the sprinters improved almost exactly as much in a variety of outcomes as the subjects doing long, sustained runs. They both increased VO2max by about 12%; they both increased 2,000-metre time trial performance by about 5%; they both lost fat (the sprinters lost 1.7 kg while the long-runners lost 0.8 kg). So yes, the HIIT paradigm is applicable to running.

But the study offers one more twist. They measured maximal cardiac output (Qmax), which is the biggest volume of blood your heart can pump in a given amount of time. In this case, the long-runners increased Qmax by 9.5%, while the sprinters didn’t improve at all.

To understand what this means, consider that VO2max (the maximal amount of oxygen you can deliver to your muscles in a given amount of time) is the product of two quantities: Qmax (how much blood your heart can send to the muscles) and “maximal arterial-mixed venous oxygen difference” (how much of the oxygen sent to your muscles is actually extracted from the blood and used by the muscles before the blood heads back to your heart). This latter quantity (the researchers write) depends on “O2 delivery to active muscle fibres (blood flow distribution, capillary density, and arterial O2 content), local enzymatic adaptations, and mitochondrial density/volume.”

So what the study tells us is that short sprints and long, steady runs both increase endurance, but they do it in different ways. Sprints act peripherally (i.e. the muscles), while long runs act centrally (i.e. the heart).

Of course, nothing is quite so black-and-white in real life, and many types of training session will stimulate both types of adaptation. Still, it’s a good reminder that the best training programs will balance different types of stimulus — which is, of course, what every elite runner already does. But those looking to HIIT as a way of getting fit should ideally try to also make time for at least one more sustained session each week.