AMAGASAKI, Japan — Japan, a country not known for its overweight people, has undertaken one of the most ambitious campaigns ever by a nation to slim down its citizenry.

A poster at a public health clinic in Japan reads, "Goodbye, metabo," a word associated with being overweight. The Japanese government is mounting an ambitious weight-loss campaign.

Summoned by the city of Amagasaki one recent morning, Minoru Nogiri, 45, a flower shop owner, found himself lining up to have his waistline measured. With no visible paunch, he seemed to run little risk of being classified as overweight, or metabo, the preferred word in Japan these days.

But because the new state-prescribed limit for male waistlines is a strict 33.5 inches, he had anxiously measured himself at home a couple of days earlier. “I’m on the border,” he said.

Under a national law that came into effect two months ago, companies and local governments must now measure the waistlines of Japanese people between the ages of 40 and 74 as part of their annual checkups. That represents more than 56 million waistlines, or about 44 percent of the entire population.