While I'm carrying a little more body fat than I'd like, I am in good shape. I run half marathons several times a year and, until 2009, did several weight training sessions weekly at a local gym. I wasn't sure Wii Fit would be enough of a workout for me, but I love gadgets and so was excited to give it a try.

What makes Wii Fit truly revolutionary is the Balance Board accessory. Basically a white plastic plank about one by two feet, the Balance Board is both a scale and a way for the Wii to know exactly where your body's weight is positioned. The system picks up even the slightest shifts in weight and balance and translates them into movement. There are a few games available that use the Balance Board, mostly skiing and snowboarding, but I'm sure more will come as developers understand the potential.

Calculating your body mass index and fitness age
While Nintendo does encourage using the Wii Fit for exercise, I find that the system is more geared toward posture and balance than toward weight loss. For each day's body test, you stand on the Balance Board, trying to remain still and centered, while the system determines your center of balance, degree of stability, and your body mass index (BMI).

BMI is calculated by dividing your body weight by the square of your height. It is generally reasonably accurate for sedentary people, but gives unrealistic results for the muscular as muscle weighs more than fat. It's also not recommended as an assessment method for children. It is, however, a simple way to give an approximation of your relative body type, and I'm not sure Nintendo could have found a better one.

Calculations complete, the system announces, "That's obese!" or "That's overweight!" in a ridiculously cheery electronic voice.

The body test ends with two balance tests and then the system calculates your Wii Fit age. Supposedly this is based on your real age and the results of your tests, but in practice I've seen everything from 23 to 56 without any significant difference in my test results from day to day.

Nintendo has done a nice job of displaying your data without giving away more than you might like. In Figure A, for example, you see my weight graph for the last few weeks, but the start weight isn't shown. No worry of accidentally telling someone your weight if you'd prefer to keep that secret. You can even put a password on your information if you feel the need.