NOUAKCHOTT, Mauritania — At the Olympic Sports Stadium here, a collection of dun-colored buildings rising mirage-like from the vast Sahara, about a dozen women clad in tennis shoes and sandals circled the grandstands one evening in late June, puffing with each step.

Between pants came brief explanations for their labors. “Because I am fat,” said one, a dark-eyed 34-year-old close to 200 pounds. Another, a 30-year-old in bright pink sneakers, said, “For myself, for my health and to be skinny.” It is a typically Western after-work scene. But this is the Islamic Republic of Mauritania, the mirror opposite of the West on questions of women’s weight. To men here, fat is sexy. And in this patriarchal region, many Mauritanian women do everything possible — and have everything possible done to them — to put on pounds.

Now Mauritania’s government is out to change that. In recent years, television commercials and official pronouncements have promoted a new message: being fat leads to diabetes, heart problems, high blood pressure and other woes. The joggers outside the Olympic stadium testify to their impact: Until lately, a Mauritanian woman in jogging shoes was roughly as common as a camel in stiletto heels.

But in other respects, the message faces an uphill run. A 2001 government survey of 68,000 women found that one in five between ages 15 and 49 had been deliberately overfed. And nearly 70 percent — and even more among teenagers — said they did not regret it.