Sweating, panting and some groaning, 400 Japanese worked out on Sunday with U.S. fitness guru Billy Blanks, whose military-style exercises have become a huge hit in a country where waistlines are bulging.

Overweight adults are far rarer in Japan than in the United States, but the government says millions of Japanese now suffer from metabolic syndrome -- a condition characterized by excess fat around the abdomen, high blood pressure and high cholesterol.

As worries over metabo grow, Japanese have snapped up Blanks's four-set DVD, Billy's Boot Camp, in droves. Marketing officials are mum on figures but media reports say around 500,000 sets have been sold.

Fans say the appeal of the workout is not only in the fast-paced combinations of kicks, jabs and squats set to thumping music, but also Blanks himself, known in the United States as trainer to the stars.

Keep your legs up, he shouts. Let me see your power.

Blanks, 51, in Japan for a 10-day promotional visit, told fans who showed up for a live workout session that it was imperative that they do not quit the program.

Who's the boss? Is it the exercise, or is it you?, he said after taking the crowd through 30 minutes of non-stop moves, said to be modeled after training exercises conducted by new recruits in the U.S. army.

Well, let me see it. Let yourself see it. Otherwise, why do it?

Sweat-drenched fans said they were hooked on the workout, launched in the United States in 2003 and which is available in Europe and South America.

I've tried a lot of exercises, but I think the tempo and the feeling that everyone's doing it appeals to Japanese, said Reiko Munakata, 46, who works for a health food company.

While television programs have played up the large number of Japanese who have quit the workout complaining of its high intensity, Osamu Ito, 34, said he still exercises with it two to three times a week.

Every time I get a health check, the results say I'm overweight, the system engineer said sheepishly.

I have to start worrying about getting diabetes.

Japan