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'Cool' workouts could be the next hot fitness trend

Karen Weintraub
special for USA TODAY

The floor is puddled in sweat. Dark circles spread down necklines.

At BFX Studio in Boston, exercisers do their routines with the thermostat set to 62 degrees,

“You can do it!” fitness instructor Kelly Brabants shouts over the screaming music. “Just a few more!”

Twenty-five people are pushing themselves to the limit, but the basement workout room at BFX Studio in Boston remains almost chilly. The thermostat is set to 62 degrees.

Brabants is testing out a new theory for fitness and weight loss: that cool workouts are better than hot ones because of a special type of fat whose stores are "activated" by the cold to produce heat.

At the nearby Joslin Diabetes Center, researchers have been studying that fat, called "brown fat." Instead of accumulating in love handles, brown fat is generally stored at the back of the neck, the scruff. It is not fat as we generally conceive of fat, which is stored to be used as energy at a time when we don't have food. Instead, this fat creates heat by burning energy — which means burning calories.

It had been thought that only younger children had brown fat. That’s how they stay warm, despite being so small. From an evolutionary perspective, its purpose is to allow babies and children to cope with cool temperatures without freezing. So, it is "turned on" and starts producing heat when the body starts to get cold, but not cold enough to shiver.

About five years ago, however, researchers at Joslin and elsewhere showed that most adults have small amounts of brown fat and that these stores can be activated by the cold.

Working out in cool temperatures, then, may offer a double benefit, says George King, Joslin’s research director.

“Not only do use up the calories from the workout itself, but you can also activate the brown fat, which burns up calories and generates heat,” he says.

The ideal temperature is about 60-62 degrees Fahrenheit, King says — cold enough to feel cool, but not so cold that it triggers shivering or tightens up muscles. (Why aren’t people in cold climates naturally thinner than those in warm ones? “Our eating can always catch up," King says.)

It’s not yet clear how many extra calories a cold workout might burn — though it’s probably not a huge amount, says Aaron Cypess, a clinician and researcher at the National Institutes of Health, who studies brown fat and worked at Joslin until recently.

For most people, the extra calories used in the cold are probably not enough to justify changing the thermostat or their workout routine, he says.

“My advice is exercise in whatever way you like it best,” Cypess says. “I want you to be there doing (exercise). I don’t care how you’re doing it.”

But for young, already fit people who go to the gym 5 days a week, “then, yes, I think it probably could give you more benefit to do it in a cooler environment rather than room temperature, and certainly better than doing it in the heat,” he says.

Activating brown fat is probably not the answer to the nation’s obesity epidemic, says Michael Jensen, a professor of medicine at the Mayo Clinic in Rochester, Minnesota, where people know something about the cold.

The body’s temperature naturally rises with exercise. Turning on brown fat requires a drop in body temperature; so, Jensen says, it may not be physically possible to exercise and activate brown fat simultaneously. Plus, people might eat more to compensate for the extra calories burned.

And even “if you were somehow magically able to turn all your body fat to brown, the increase in your core temperature would probably kill you,” Jensen says.

But Jensen says he still thinks it's a better idea to exercise in a cool gym than a hot one, and to expose a lot of skin.

It may do nothing for your brown fat, but the cooler temperatures and scantier clothing will whisk away sweat faster. You’ll feel more comfortable, avoid dangerous overheating and get the same benefits as a “hot” workout, Jensen says.  “You can probably go longer and do better than if you’re exercising in a warm condition."

For long-time diabetics, cool workouts may be even more important, Jensen says. They often lose the ability to cool off through sweating, putting them at risk for overheating.

Isn’t there any advantage to sweating bullets as you power through hot yoga or an intense exercise routine in a sweltering gym? “I can’t think of one,” Jensen says.

For those at the BFX Studio last week – pounding punching bags, hoisting bell-shaped weights, and alternating push-ups with leg kicks – the cooler workout simply felt good.

“When it’s too hot it makes me nauseous,” says Allison Cipriano of Brookline just after the hour-long boxing and bells class. “I definitely liked this a lot.”

Kate O’Sullivan of Boston says she thinks the cooler temps made her push herself harder because she didn’t get the signal from sweating that she was reaching her limit.

Brabants, who was teaching her first cold workout, said it felt refreshing and energizing to work out in the cooler room. She says she’s not yet ready to give up her hot classes yet — “I love the sweat” — but plans to make the cold class a weekly feature.

“If you can burn more calories and burn more fat, I don’t care what you have to do,” Brabants says. “I’m going to do it.”

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