BUENOS AIRES — From a lazy person's perspective, humanity is divided into two categories: those strange people in love with physical activities, who keep telling you how good they feel and how their body "needs" it, and the rest of us.

The idler has no problem grasping this clear concept: You need to walk at least a half-hour a day to lose weight and not be sedentary, or get off the bus two stops early or join a gym and then spend your energy actually going rather than making feeble excuses not to.

The lethargic person knows this but does not do it: He or she is always pressed for time or tired, or bored just thinking about sit-ups. But — good news! — something has changed in this sorry tale. In Argentina, many gyms are including dance classes in their programs, which has led the formerly inert not just to come and dance, but perhaps to their own disbelief, come back for more. Dancing is helping them lose weight and be happy, and for the first time they too are finding that their body "needs" it.

It is not about learning dance techniques like in an academy, but imitating dance movements to be active. You can now dance Latin rhythms, hip hop, Arab belly dancing or tango in more than half the country's gyms, according to Mercado Fitnessmagazine.

The trend has led Megatlon, a chain of gyms, to launch Megafest — a ballroom dancing class — while instructor Andrea Bellucci, has created "Move it, we can all dance" (Muévelo, todos podemos bailar), a program in which she says "I work on the basis of each person's temperament and emotions."

But the most popular dance activity of the moment is unquestionably zumba: a routine created by three Colombians who now have trained instructors in 180 countries, and which includes such fierce loyalists as Shakira, J.Lo and Rihanna.

"It's a combination of international rhythms, it's easy and intense, and the instructor can surprise them" with the choice of music, says Darío Micillo of Zumba Fitness Argentina.

He says instructors work with a range of music including wedding songs, Frank Sinatra or Palito Ortega, an Argentine crooner of the 1960s.

Getting hooked

So, who is driving the beat of the zumba craze? "Women aged between 30 and 50, especially. We have won back the women who used to do aerobics in the 1990s. With their children grown up now, they are looking for something to do to feel both healthy and cheerful," Micillo says.

But can you actually lose weight while having so much fun? "Dancing burns between 300 and 500 calories an hour, equivalent to a brisk walk or riding a bicycle. If an adult dances an hour a day and eats 300-500 calories less a day, she could lose, healthily, two to three kilos a month," says nutritionist Silvio Schraier.

The key to this furor however is also in the fact that "dancing helps fight stress, because it increases the influx of endorphins, the substance that makes us feel well," says Schraier, a doctor at the Buenos Aires Italian Hospital. "In terms of the heart and breathing, it boosts oxygenation and blood circulation. It also reduces arterial pressure and helps lower cholesterol, triglycerides and glucose."

What about the brain? Argentine neurologist Ignacio Brusco explains that when you learn a dance, you activate several zones in your brain, spacial zones (that let you see space and feel your body), motor zones (which improve motor coordination and the part of the brain that learns processes, like driving), and emotional zones (activated by the emotions provoked by the dance and music).

This is an option with sufficiently clear benefits to have doctors sending their patients to do it. "Just joining is the first advantage," says Jorge Franchella, a sports doctor at the Clínicas hospital. "When I tell someone they have to walk every day, they tell me it's boring and don't do it. If I tell them they have to dance, it's a different story."

Dance instructor Romina Samelnik says "some do come initially on the doctor's orders, but they end up hooked for other things. They loosen up here, pretend they're doing a show, learn to laugh, even at themselves, and manage to forget all the day's problems."