I nervously typed the numbers onto the Web site -- first my height, then my weight. I held my breath and clicked "Calculate."

"Your BMI: 25.4," was the clinical response from the Center for Disease Control and Prevention's body-mass-index calculator. In other words: "Happy New Year, chump. You're overweight."

BMI, or weight in kilos divided by height in meters squared, is one gauge of a person's percentage of body fat. Someone rated 25-29.9 is commonly considered overweight; anyone topping 30 is obese.

I'd never thought of myself as flabby, but there on screen was proof that my thirtysomething bod wasn't burning off the holiday food and drink as quickly as it used to. I braced myself to read on.

According to the CDC site, about a third of adults in my native United States are obese. And being overweight or obese increases the risk of hypertension, type 2 diabetes, heart disease, stroke, cancer and many other ailments, it said. Yikes.

The Web site of the Ministry of Health, Labor and Welfare, revealed that things aren't much better in Japan, where nearly a third of men in their 30s are overweight. So even all that fish and fermented soy beans doesn't exempt anyone from pudginess.

I resolved that my membership of this Chub Club needed to be terminated. But how?

At my local bookstore, the fitness-section shelves groaned under the weight of how-to books on golf (not my cup of tee) and getting pumped like Mr. Universe (as if I had the time and perseverance). Then one title published last year jumped out at me: "Taishibo ga ochiru toreningu (Training Body Fat Away)." The subtitle got me even more excited: "Remodeling Your Body on 10 Minutes of Quick-Slow a Day."

I had no idea what "quick-slow" meant, but the "10 minutes" part sure sounded great.

Authored by Naokata Ishii, a professor of exercise physiology, and Michiya Tanimoto, a researcher of muscle physiology -- both at Tokyo University -- the book said keeping fat away requires the build-up of "fast muscles" -- the ones used for power and speed. ("Slow muscles" dispense force over long periods, as in endurance running.)

The focus on fast muscles, the toning tome explained, is because they produce "uncoupling protein 3," or UCP3, which plays a key role in converting energy in sugar and fat to heat.

In "quick-slow training," quick exercises are paired with slow ones to build muscle without hours every week spent in a gym. "Naturally, the risk of hurting muscles or tendons is tiny compared with using heavy weights," said the authors.

This is how it works. "Quick exercises," such as specialized squats and push-ups, are designed to produce maximum force to break down muscle tissue to "bulk up," in the jargon of body-builders.

Force, as we all learned in school, equals mass times acceleration. So the authors use simple math to argue that with the body providing needed mass, accelerating -- or speeding up -- during exertions helps make up for the lack of heavy weights.

Each fast exercise is followed by a slow one working the same muscle group. Keeping the muscles taught is said to set off the secretion of growth hormones that aid the rebuilding of the broken-down tissue, so rapidly increasing muscle mass.

One example of a 10-minute course of quick-slow exercises starts with 50 "rhythmical knee-ups"; that's followed by 10 quick "squat jumps" and 5-10 slow "normal squats"; 10 quick "bend-over rowing" movements with light weights and 5-10 slow "rear-raises" with light weights; 15 seconds of "quick sit-ups" and 5-10 slow crunches; and finally 15 seconds of quick "knee-to-chests" and 5-10 slow "leg-raises."

The brainy path to brawn, I thought as I stood there mouth agape. Near the back of the book I found a photo of professor Ishii at age 46 -- shirtless and rippling with muscles. That seemed to vouch for his program's efficacy and I tingled with excitement at the thought that I could look like an athlete by June.

Too good to be true? I needed a second opinion.

I called ISSA-certified personal-fitness trainer Julie Suga, 53, who teaches sports nutrition at the Fuji Athletic & Business College in Tokyo and health care at Tokyo Union Church.

Suga, a former body-builder herself, agreed with the quick-slow premise and echoed the view that extreme exercise isn't necessarily a good thing. Indeed, she said, it can result in weight gain over time.

But Suga took a different approach to shedding blubber -- suggesting that beginners try 30 to 35 seconds of sprinting or cycling at near-maximum effort, followed by 2 minutes at about half that level. Repeat five to eight times, each day, five or six days a week.

This should be preceded by six minutes of warm-up and followed by cool-down of the same length. (The Ishii-Tanimoto book also stressed the importance of limbering up muscles.)

Suga said her method encourages production of a fat-burning hormone called glucagon. Following the correct diet and exercise regimes can yield weight loss of 0.45 kg to 0.9 kg a week, she said.

Ah, the operative word being "correct." Suga thought this took professional guidance.

"You can't stay on the same method for one year, two years, three years -- no way," she told me. "Somebody has to supervise this."

Whoa! I thought to myself. Aren't personal trainers for the rich and famous? For now, I'd have to embark on this journey solo. Well, I did! And boy am I glad about it.

Right now, I'm following the 10-minute regime because, well, it takes just 10 minutes. My mood has improved and my body is wonderfully energized. I feel like a new me!

OK, so maybe my exuberance is premature. I've only been on this new year's fitness kick for two days. And I've already lapsed now and then, like when cookies were handed out at the office. And when my friend insisted on another round of beers. And there were those mint chocolates . . .

But I will prevail! Today no motto sounds too cheesy, not even Lao Tzu's chestnut: "A 1,000-mile journey begins with a single step."

I'm way past that. I climbed 51 steps to the third floor today, totally shunning the elevator. Maybe I'll be jogging from the station to the office next week. Or maybe I won't . . .