Who doesn’t want to be fit and buff, and look like Angelina Jolie or the male equivalent? And who isn’t attracted to the idea of getting to look this way by playing video games?

I may be wildly out of shape now, but ’twasn’t always so. In a previous life—20 years seems like a long time—I was quite the athlete. I was into soccer and football, and even played hockey at a competitive level right up until university.

It was a grudging admission that led me to pursue a degree in sports psychology: I was probably never going to play in the NHL, but maybe I could get there some other way.

One thing I learned is that fitness, rather than weight, is the most important indicator of a person’s health. Athletes, for example, tend to be heavier because muscle is denser than fatty tissue. The best way to find out a person’s fitness—or lack thereof—is to give him or her a VO2 max test. This involves measuring a subject’s oxygen intake and output while he or she runs on a treadmill or rides a stationary bike. The test calculates how efficiently a person’s body sends oxygen to the muscles.

It would have been pretty hard to build a VO2 max test into the Wii Fit, released in May. (The game costs $100 and ships with a balance board, a small step that can measure pressure.) Instead, Nintendo designers decided to use body mass index as a way of measuring the progress of users. Wii Fit is a game, after all, and games—at their core—are about achieving goals.

The problem is that BMI—derived from a person’s weight and height—doesn’t measure a person’s level of fitness. It’s a reasonably effective tool for identifying obesity in groups of people, but for individuals it’s too blunt an instrument.

Which is why Wii Fit is branding scores of average, athletic people as fat. People with more muscle or greater bone density aren’t necessarily fat, even though they weigh more. Most adults should be able to critically assess the game’s claim; it’s the kids I’m worried about.

Kids already face enough problems related to body image and social stigma without a video game calling them fat. Players should ignore the BMI–benchmarking aspect of Wii Fit and just enjoy the games.

Nathan Mellalieu, head trainer and president of Studeo 55 in downtown Vancouver, installed a Wii in his fitness club a year and a half ago, and started using Wii Fit with his clients when it was released. His trainers don’t use the diagnostic tool that’s built into the Fit, nor is the Fit a core component in a client’s program. Instead it’s used for active rest, as a way of keeping the body moving—and the blood flowing—when catching your breath after particularly gruelling exercise.

What’s a video game doing in a fitness club? “It fits,” punned Mellalieu in an interview at the club. Having watched his nieces and nephews get out of breath while playing with the Wii, he began to consider bringing the console into the facility. But all gym equipment there, he explained, has to meet three criteria. “Is there a risk to clients? No. Is there a health benefit? Yes. Is it fun? Yes,” he said.

After a proper warm-up, I stepped onto the Fit balance board ready for some gaming. I started with a recreational jog, which had me running in place while the virtual Mii jogged through a park. The Wii Remote in my pocket measured my pace and the amplitude of my stride, and translated this into my Mii’s speed on the screen. The jogging feature doesn’t include the ability to set intervals, or provide pacing assistance—something I really need when jogging—but I expect those will be future enhancements.

I was surprised at how difficult some of the tasks were. I was able to execute an average performance while doing a pushup and side plank exercise—I hope my yoga instructor takes note—but the only reason I reached the end goal was that I’ve done the movement before while being guided by a professional. I can’t imagine someone in their living room—especially a novice—being able to figure out how to move from pushup to side plank and back again, let alone becoming proficient at it.

Mellalieu said he was pleased that the developers included an aerobics component with the Fit, and didn’t rely solely on balance and strength games. The major drawback, he said, is that while the Wii is able to measure a push using pressure sensors on the board, it can’t measure a pull, which is half of any movement.

What the Fit is very good at is providing feedback about balance. As I did a series of rowing squats, the Fit was able to get me to adjust my weight back onto my heels, simply by displaying a point of light and telling me to keep it in a particular area of the screen through my position on the balance board. The game was able to help me refine my movements and body position faster than an instructor or coach could have.

One of the other lessons I learned studying sports psychology is that a person’s perceived efficacy—how capable a person believes he or she is of accomplishing a task—is an important indicator of how likely a person is to continue attempting that task.

The Wii Fit is an important addition not just to the oeuvre of gaming but to our constantly changing society, because it will increase a person’s self-efficacy for jogging, doing pushups, or learning proper posture. And that might get more people doing those activities away from their TV.

Using the Fit is a fun, engaging way to add some physical activity to your life. It won’t turn anyone into an athlete, but it’s a—pun intended—step in the right direction.