NEW YORK If outdoor fitness has been your road not taken, summer may be perfect time to ditch those climate-controlled Pilates classes and take a hike.

“The Green Mountains of Vermont is the gym in our backyard,” said Jimmy LeSage, owner of the New Life Hiking Spa in Killington, Vermont. “You get to be in nature. It's more tranquil.”

Although the spa offers other activities, its centrepiece is hiking, which can mean anything from a leisurely nature jaunt to an arduous trek up a mountain.

“You get stronger, you lose weight, you de-stress,” said LeSage, a former ski bum who has been ushering weight-conscious clients through the Green Mountains for more than 20 years.

Hard economic times may be driving more budget-conscious Americans to move their fun, and their fitness, out of doors.

The Outdoor Foundation, a non-profit association of the outdoor recreation industry, reported that participation in hiking grew by nine per cent in 2008.

Traversing hills, especially while carrying a backpack, burns calories, strengthens muscles and can prove addictive enough to uproot even the most stubborn couch potato, according to Dr Patty Freedson of the American College of Sports Medicine.

“Hiking doesn't take a lot of skills and can be done with group support,” she said. “Most important, it's enjoyable. If you can get a sedentary person to do one or two miles and sustain it, that would be great.”

The Fatpacking company, based in Hull, Massachusetts, likes their hiking-for-weight-loss treks spiked with camping and wilderness training.

“I also call it 'fitpacking' because people don't want to tell other people they're going to Fatpacking,” said company founder Steve Silberberg.

Silberberg, who left a career in computer programming to indulge his inner boy scout, said his expeditions, while geared to weight loss, are not for the morbidly obese or the faint of heart.

“It's not for couch potatoes or 'Big Loser' types,” he said, referring to the popular television show that helps people lose weight. “Over steep terrain with a huge pack on your back, you get a cumulative fatigue. Thighs and butts tend to get a bit bigger because of increased muscle mass. Body composition changes a little bit.”

Bree Gotsdiner, an occasional co-guide, said people often use Fatpacking treks to jumpstart a diet.

“People always lose fat, always gain muscle,” she explained. “(Food) portions are limited to what we carry,” the former fire-fighter, said, adding all guides are EMT and wilderness certified.

“You need different skills when you're in the forest than when you're in the city.”

Silberberg said the most important thing to pack is a good attitude, but he admits the expeditions may not be for everyone.

“We hike whether it's rain or shine or snow,” he said. “If you think you're going to be unhappy without electricity or plumbing, maybe it's not for you.”

This winter Fatpacking plans to tackle the Haute Route in the Alps. But that journey may see clients forgoing sleeping bags for warm beds.

“We work with what's available,” Silberberg explained.

“People are not as willing to camp out if they know that there's an inn a mile away.” —Reuters