[pullquote source="] [i]This article was taken from the April 2013 issue of Wired magazine. Be the first to read Wired's articles in print before they're posted online, and get your hands on loads of additional content by [link url="https://www.circules.com/subscribe/wired-uk/60606"]subscribing online[/link].[/i] I'm in the foetal position at the bottom of a swimming pool. Water temperature: 15 degrees celsius. A 9kg weight is anchoring me in place. All I'm wearing is a pair of Speedos, a nose plug, goggles and a snorkel resembling an oversized asthma inhaler. The mouthpiece connects to two 1.2-metre hoses feeding into a PC-sized box next to a laptop. I'm shivering intensely and have an unbearable headache. My suffering is natural, I tell myself. It could even be good for me. After 20 minutes, my torturer, Ray Cronise, signals that my time is up. A former Nasa material scientist who spent 15 years overseeing experiments aboard shuttles at Marshall Space Flight Center, Cronise is testing me at his home in Huntsville, Alabama. That snorkel contraption -- a $30,000 (£19,000) piece of kit -- is analysing my breathing to chart how the cold water affects my metabolism. (It tracks inhaled and exhaled carbon dioxide and oxygen, a proxy for the amount of fuel I'm burning.) He believes exposing the body to cold can be an effective spur for losing weight and is undertaking this research in the hope of formulating a Weight Watchers-style algorithm, app or device that can help people harness what he's convinced is the transformative power of cold. Cronise got the idea in 2008 while watching a TV programme about Michael Phelps. The coverage claimed that, while training, the US Olympic swimmer ate 12,000 calories a day. At the time, Cronise was on a diet of 12,000 calories per week. (He was carrying 95kg on his 1.75m frame and wanted to get back down to 82kg.) Something didn't add up. Even if Phelps had an exceptionally high metabolism and swam three hours a day, he still should have turned into a blob. Then it hit Cronise: Phelps was spending hours every day in water, which was sucking heat from his body. He was burning extra calories just to maintain his core temperature of 37 degrees celsius. That autumn, Cronise grew obsessed. He took cool showers, wore light clothing, slept without sheets and took five-kilometre "shiver walks" in freezing weather wearing a T-shirt, shorts, gloves and earmuffs. In six weeks he shed 12kg, nearly tripling his weight-loss rate without changing his calorie-restricted diet. [Quote"] [/pullquote]

Cronise set off on a full-blown weight-loss fad. In 2010, he talked about his self-experimentation in a presentation, and then the Pied Piper of body-hacking, Timothy Ferriss, name-checked Cronise and prescribed 20-minute ice baths in his book The 4-Hour Body. ABC's Nightline aired a segment on Ferriss and "thermal dieting". Right on cue, bloggers began documenting their own cold-exposure experiences. On websites and forums such as fatburningman.com, diehards started sharing tips on making DIY ice packs. "My body," one guy confessed after sleeping with ice-filled Ziplocs on his abs, "felt like it had been beaten with heavy sticks." Today the trend has gone truly mass: diet books such as Six Weeks to OMG:

Get Skinnier Than All Your Friends urge readers to take cold baths. On Today, a US daytime TV show, presenter Kathie Lee Gifford praised a company called FreezeAwayFat, which sells Lycra bike shorts with pockets for frozen gel packs.

Just one problem: there's not much rigorous science behind any of this. It's exceedingly difficult to quantify how environmental temperature affects an individual's metabolism. Studies have shown cold exposure can boost the metabolism anywhere from eight to 80 percent, depending on variables including the degree and duration of the exposure, your diet, age, gender and fat mass.


Scientists are racing to separate the science from the pseudo. They're investigating the mechanisms by which the body adjusts to the cold and learning how our bodies burn fat. They're even trying to come up with a new kind of weight-loss pill -- a longtime ambition of the pharmaceutical industry -- that can mimic those processes and make us thinner faster, with less effort.

But Cronise doesn't have plans for a pill, backing or VC funding. He's not waiting for peer review. He wants to see results -- now. That's why he's got me submerged in his plunge pool. He's conducting his own experiments, trying to figure out how much cold affects metabolism, how best to administer the cold, and for how long.

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After 20 minutes in the pool, I emerge from the water, but I'm still breathing through the snorkel.

Cronise wants to monitor me for any sustained acceleration of my metabolism for at least 30 minutes. The air temperature is 30 degrees celsius. I can't stop shivering.


Eleven hundred kilometres away, at the National Institute of Diabetes and Digestive and Kidney Diseases in Maryland, Kong Chen is conducting his own (it must be said, more rigorous) experiments to understand the effect of cold on human metabolism. Chen, the director of a team of researchers at the institute, studies something called thermal neutral zone. It's a range where the body requires very little energy to maintain its core temperature. It's a state of biological equilibrium with the environment.

Researchers want to understand the physiological mechanisms at work when mammals live in a thermal neutral zone and what changes in colder conditions. Little is known about the zone in humans. "We're only in the infancy of getting to know the body better," says Chen. To fix this, he's charting metabolic variability among lean and obese people exposed for up to five hours a day to air temperatures between 16 and 31 degrees celsius. That way he can map the variables that lead to different thermal neutral zones and learn why some people burn more calories at lower temperatures.

One of the crucial variables Chen has been studying is brown adipose tissue (BAT). Unlike white fat, which merely stores calories, brown adipose cells burn them to produce heat. When your body gets cold, this metabolically active tissue kicks into gear to warm you up. BAT tends to be scattered in little deposits throughout the upper back and neck. Rodents and hibernating mammals have a lot of brown fat. Humans are born with a healthy supply to warm them once they're outside the womb. But for decades it was widely believed that the tissue vanished before adulthood.

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Adam Voorhes

In the 70s, autopsies occasionally turned up unusual tissue samples suggesting some adults might maintain reserves of BAT. But they were rare enough to be discounted. Then in 2004, Jan Nedergaard and his wife, Barbara Cannon, both physiologists at Stockholm University, noted an anomaly. While conducting PET scans in search of tumours, some radiologists had noticed dark spots in cancer patients' necks.

Typically, such findings -- which indicate areas of elevated glucose uptake -- were signs of tumour presence. But tumours are irregularly shaped, and these spots were symmetrical. They realised it must be BAT. The pair published a review of the PET scans in 2007 in the American Journal of Physiology - Endocrinology and Metabolism.

In spring 2009, three papers published in the same issue of The New England Journal of Medicine established that BAT exists and is functionally relevant in at least some adults. One of the studies was coauthored by Aaron Cypess, an endocrinologist at Beth Israel Deaconess Medical Center in Boston. He and his colleagues had dug through his hospital's records and examined 3,640 full-body PET-CT scans. Sure enough, there were plenty of symmetrical spots. He acquired a biopsy specimen from the pathology library to corroborate the scans. Under a microscope the tissue sample was confirmed -- they were brown fat cells.

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This discovery has set off a flurry of research into the prevalence of BAT and the ways it might be tapped to accelerate weight loss. In adults, BAT activates within minutes when the body loses heat; experimenters often trigger it by exposing subjects to temperatures between 16 and 19 degrees celsius. So BAT researchers now routinely chill subjects before placing them in PET-CT scanners. The hope is that by stimulating more of the tissue to "turn on" -- and light up in the scans -- scientists can better determine who has more brown fat and why.

At Beth Israel in July 2012, Cypess stood over a trim 23-year-old male volunteer, one of 19 paid lab rats that Cypess is examining for his follow-up study. "I have no idea if he's gonna have BAT or not," says Cypess. "We're on the verge of statistical significance."

The medical centre has a designated cold room for BAT studies. It's a windowless vault with a gurney and 21-inch television. To administer the cold, Cypess puts the volunteer in a vest lined with blue plastic tubing that circulates 14-degree water around his torso. We watch The Wedding Singer on VHS while his blood is drawn and he receives a 12-millicurie intravenous injection of 18F-fluorodeoxyglucose, an isotope tracer that is taken up by tissue just like glucose.

When Cypess looks at the resulting scan he sees four symmetrical black splotches within the grey-and-white outline of the volunteer's body. According to preliminary analysis, the subject has 70g to 100g of BAT -- enough to fill one, maybe two shot glasses. That's an above-average amount, based on the data that exists. For a more precise figure, Cypess will scrutinise the 50 axial slices of the subject's PET-CT scan, which could take many hours.

Cypess will spend months tabulating his results. Then he will comb through the blood work -- the levels of glucose, pyruvate, fatty acids, lactate and norepinephrine. He hopes to uncover correlations between a subject's quantity of BAT and the chemicals that are most active when that person's metabolism is stimulated by cold.

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Cypess warns that until more studies are completed, dieters should be wary of freezing themselves to get skinny.

If cold speeds-up weight loss, and if the effects of cold are the result of an underlying physiological process, then it follows that theoretically you could synthesise a drug to induce that physiological process without ever having to bother with cold exposure. In other words: a magic diet pill. That possibility is enticing to drugmakers.

More than 30 percent of adults in the US are obese (in England, it's 26 percent). It's easy to fathom the broad appeal and potential payoff of a weight-loss pill that can activate BAT -- or spur its formation in the body. "Every major pharmaceutical company is interested in brown fat right now," says Lou Tartaglia, CEO of Ember Therapeutics, a Massachusetts startup that in 2011 raised $34 million (£22.5 million) to develop BAT pharmaceuticals. In January 2012, Ember cofounder Bruce Spiegelman, a Harvard professor and Dana-Farber Cancer Institute researcher, published the identification of a hormone he named irisin, which transforms white fat into brown fat -- a process called browning.

And in July, Spiegelman's team isolated a third type of fat cell, one that's neither white nor brown. Dubbed beige fat, this third distinct tissue can be found within white fat cells and functions much like BAT.

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Ember just has to distill all these developments into a pharmaceutical cocktail: a bit of irisin and maybe a dash of the growth factor BMP7 to brown your white fat, then a few other proteins to jump-start the metabolic process that causes energy-burning.

Every major pharmaceutical company is interested in brown fat right now Lou Tartaglia, CEO, Ember Therapeutics

Tartaglia isn't wasting time. Last September Ember opened a 1,400 metre squared office with a wet lab in Watertown, Massachusetts and went on a hiring spree. He says he expects Ember to begin testing its first BAT drugs on primates by the end of 2013. But even if all goes according to plan, drugs for humans won't hit the market until at least 2020.

Critics say the whole effort misses the point. "Obesity is not a disease of insufficient BAT, but rather one of overconsumption and reduced calorie expenditure: couch potato-itis," says Shaun Morrison, a neurobiologist studying BAT at Oregon Health & Science University. "Obese individuals will simply eat their way through the therapy and remain obese."

Cronise, the man who kicked off the freeze-yourself-thin fad, doesn't care whether BAT is responsible for his weight loss. His obsession is figuring out how people can most effectively lose weight, not why. And he's concerned that some of his acolytes have adopted "stupid crazy" tactics -- cold showers, frigid ice baths -- that can be uncomfortable, dangerous and unnecessary.

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Cronise thinks there's a way to lose weight without subjecting your body to extreme temperatures.

Studies have shown that the same thermogenic mechanism used by BAT also occurs in skeletal muscles during cold exposure. Before you shiver, your muscles produce heat -- just as BAT does. The findings suggest that exposing yourself to less extreme cold could still be beneficial -- even if you have very little BAT.

Since 2008, Cronise has tried to invent a user-friendly way for people to tap into the power of cold exposure. By 2010 he settled on his ultimate goal: a wearable device that would make it simple for anybody to shed weight. It would have a temperature sensor and could connect wirelessly to an app on your laptop. You'd type in what you were wearing and the software would factor in the ambient temperature and estimate the net effect on your metabolism.

Cronise started by modelling some basic assumptions about the body and creating a unit of measurement he called thermal load. The idea was to boil all the variables down to one simple number that helps people understand the amount of cold exposure they're getting and then approximate its impact on metabolism. Cronise has filled ten binders with notes, journal articles and data about his own energy-use patterns.

But to build his dream device he needed more data, so in 2011 he spent $1,500 (£990) building his own calorimeter out of sensors from LabQuest, a continuous positive airway pressure (CPAP) mask normally used for treating sleep apnea, and a lunchbox-sized plastic tub. He designed a custom air valve in CAD and had it 3D-printed. But it didn't work well enough, so he got a $3,000 (£1980) BodyGem, a version of the handheld device used to assess metabolic changes in contestants on the NBC show The Biggest Loser.

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In March 2012, Cronise turned off his home thermostat, opened his windows and spent a month letting in the cool outdoor air. His body burned 22.5 percent more calories, without any change in diet or exercise. He was, in theory, losing weight while he was sleeping. But Cronise wanted better, less anecdotal data.

Which brings us to the snorkel-inhaler we're using in the pool. Cronise bought the Cosmed Quark cardiopulmonary exercise testing (CPET) machine in August 2012, because it's the gold standard for measuring metabolism. The setup can be calibrated to the environment and can quantify the percentage of fat versus carbohydrate that a subject metabolises.

He wants to pinpoint how various types of cold exposure burn fat.

I'm the fifth person he has analysed but the first he has subjected to water torture.

It's the final day of our experiments in Huntsville. I'm luxuriating in the sunshine. I finished a 26-degree soak -- it was more pleasant than my first 15-degree submersion. I shivered, just not as violently.

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Cronise and I are looking at my energy expenditure and respiratory quotient, or RQ, which reflects what kind of fuel I was burning. Ideally my RQ should stay as close to 0.7 for as long as possible, because that indicates 100 per cent of the energy being generated by my body is coming from fat (RQ = carbon dioxide eliminated/oxygen consumed). When RQ shoots up to 1.0, the body is fuelling itself on carbohydrates only. But sustained fat burning is the goal of cold exposure.

He walks me through the data. During and after running, cycling or swinging kettle bells and while I swam, my RQ hovered around 0.9, often spiking closer to 1.0. Not good. I was burning carbs instead of just fat.

But Cronise assures me that "slobbering in a tube underwater, looking like a bondage slave" was worth it. He points out that my RQ dropped noticeably; I was burning fat steadily every time I exited the pool. After the 20-minute swim in 21-degree water, my RQ averaged 0.73 for 15 minutes. Following a 20-minute swim in 15 degrees, I hit 0.695 for 12 minutes. After that first miserable soak in 15-degree water?

0.73 for 15 minutes.

The cold had a prolonged effect on my metabolism. The data confirms what Cronise has been saying: water is an efficient way to force the body to produce a lot more heat for a sustained period of time. If my goal is to burn fat, I'm better off swimming -- or even sitting -- in San Francisco Bay than jogging or cycling, provided I let my body warm itself naturally afterward (no hot showers or sauna allowed). "Do we know it was BAT?" Cronise asks. "We don't know. Not for sure. You were definitely burning more calories after cold exposure." Conceivably, I'm walking around with a generous supply of brown fat that makes the cold worth my while. But it could also be my muscles burning the calories. For now there's no way to know. None of the researchers I interviewed would give me a PET-CT scan. Unless it can be included in a study, one scan is pointless to them, not to mention costly: it can cost up to $4,000 (£2,600).

Cronise's data has whetted my appetite. Could less extreme measures help me maintain my weight without changing my diet? How long in a cold shower would equal my results from the pool? Do I need to measure the water temperature?


Before leaving, I head for the shower. Our last test was a 20-minute jog, so I'm sweaty and tired.

I'm about to catch a plane, where I'll wrap myself in a blanket and sit in a climate-controlled cabin for hours. I reach for the tap, turn on the water and feel the first cold drops splash my hand.

Steven Leckart (@stevenleckart) wrote about flipped universities in 05.12