We’re in the midst of a big, fat emergency. The evidence is piling up faster than the unwanted pounds of winter.

It seems that every week there’s news of yet another finding about the hazards of obesity to weigh us down.

It’s all simple arithmetic — calories in, calories out. Too many in, too few out and you have weight gain. You have to lose the couch-potato lifestyle to increase the calories-out part of the equation.

But what if you’re allergic to spandex and the notion of regimented exercise?

Then the best strategy may be stealth exercise — a workout dressed up as something else, preferably fun. Here are a few easy suggestions:

Make a play date

You can tell right away that there’s something odd about this workout session at a Boys & Girls Club in San Francisco. There’s just way too much laughing. These 10 women aren’t working out — they’re playing. And that is precisely the point.

They’re enrolled in a series of classes called Urban Recess. As the name suggests, it’s modeled on the good old schoolyard break. The group tackles complicated games of tag and other standbys of childhood, some familiar, such as Simon says and hot potato, and some not so familiar, such as hurry up, steal the bacon and duck duck goose.

“You are looked at funny if you laugh in a gym,” says Karin Schmidt, 32, the founder and instructor of Urban Recess. A former soccer player and fitness instructor, Schmidt started the program a little more than a year ago.

It’s definitely exercise in disguise: “It’s interval training, but a lot of them don’t realize that’s what they’re getting until you explain it to them,” Schmidt says.

The women in the class range in age from 21 to 62. They don’t stand in the serried ranks of the usual gym class but move into ever-changing formations — circles, lines, partnered in pairs or other groupings. They throw balls, run, shriek, collide and get red in the face.

“I’ve done yoga, pilates, weightlifting,” says Leda Wagner, 31. “I love this because you don’t feel like you’re exercising.”

Join in

There’s no excuse for not finding a softball or soccer game somewhere on a field near you. If you want to try something a little more out of the ordinary, that’s not too hard, either.

How about joining a kickball team? Yup, that game you played in grade school, where you kicked the heck out of that big round rubber ball. The World Adult Kickball Assn. was started in 1998 in the Washington, D.C., area by young adults who refused to outgrow the playground sport.

Hit the mall

You can shop till you drop — some pounds, that is, if you keep moving.

Patricia Campbell logged more than 1,000 miles and lost 37 pounds since she started walking at Arden Fair mall in Sacramento, Calif., in 2001.

“It has done wonderful things for me,” she says. “It makes my doctor happy with me, too.”

Campbell, 58, started out slow but now walks five miles in a little more than 90 minutes six days a week.

Campbell says it’s not just weather she wants to avoid: “You don’t have to worry about dogs and cats or car exhaust or, in some neighborhoods, chickens.”

Take little steps

Roberto Quintana has a simple message: Just move it.

He knows of more ways to burn calories than you can shake a stick at (stick-shaking would burn a few calories) as a professor of exercise physiology at California State University, Sacramento.

“The best way to lose body fat and improve your health is just increasing your physical activity,” Quintana says.

Just about everything counts, from ballroom dancing to moshing, from gardening to housework. And yes, sex (in case you were wondering).