FREDERICTON - Given a choice between relaxation or exercise, Rahool routinely made the kind of decision many overweight Canadians can identify with -- he'd enjoy a quick snack then curl up in a comfortable spot and snooze.

Rahool, a chubby male lab rat, would balefully eye the exercise wheel in his cage, only half-heartedly making the odd rotation - a clear sign to researchers studying him that his motivation level was lower than a rat's belly.

Meanwhile, slim rats in the research laboratory at Mount Allison University in Sackville, N.B., loved their exercise wheels and whirled around in them like creatures possessed.

New research into motivation and exercise published by researchers at Mount Allison has uncovered an unfortunate paradox when it comes to weight loss -- the key to getting motivated to jump on that treadmill is to be skinny to begin with.

Terry Belke, a researcher and psychology professor at Mount Allison, is studying what makes us want to run.

His research suggests that when it comes to shedding pounds with exercise, we are swimming against the current.

"The strongest and most powerful determinant of our motivation to run is body weight," Belke says.

"As our body weight goes down, our motivation to run goes up and presumably the rewarding aspects of running tend to also go up."

Belke says that although there may be strong social and cognitive motivations for an overweight person to start exercising, that may not be enough to overcome the instinctive desire to sit back and relax.

"Being socially and cognitively motivated might be enough to get you out and buy a gym membership or piece of exercise equipment, but unless your physiology is essentially supporting and sustaining that, you may not be able to maintain the exercise," he says.

"People tend to think of exercise as a means to lose weight but there's the other side of the coin and that is the relationship between weight loss and one's motivation to exercise."

Lynn Brooks of Halifax knows all about the motivational struggle to exercise.

Brooks has been embroiled in a lifelong struggle to control her weight and although she has managed to incorporate exercise into her daily routine, she understands the attraction of not exercising.

She says she sees the lack of motivation in many of her friends and she believes it is largely a function of modern life and the focus on convenience.

"It's not easy because our whole world is geared towards letting us do things without much movement," she says.

"We leave our houses and get into our cars and we don't even have to get out of our cars to get a cup of coffee. Everything is about convenience . . . I know people who don't move at all."

Belke says the urge to run may have evolved as a response to lack of food in an area, driving individuals to migrate.

He says that mechanism may be backfiring in today's fast food nation.

"We've created an artificial situation that really doesn't exist in the natural environment," says Belke. "We're surrounded by high-calorie food all the time, and we don't have to work hard to get it."

Belke says his findings suggest North America's obesity epidemic may be a tougher problem than imagined, but people involved in exercise education say it is possible to nurture motivation.

Rod Macdonald, vice-president of Can-Fit-Pro, a provider of fitness education in Canada, says getting involved in exercise has more to do with establishing habits than it does body type.

"One study found that the more frequently people exercised, the more likely they were to remain a member of a fitness club," Macdonald says.

"If you make it part of your lifestyle, it becomes a habit. Once it comes a habit, you don't have to think about it, you don't have to make time for it - you just do it because it's part of your life."