RIO DE JANEIRO - Brazilians' waistlines are bulging, belying the country's image as a place of buff sun worshipers and lithe soccer players.

Nearly half of adult Brazilians are overweight and about 15 percent are obese, Brazil's IBGE social statistics agency said on Friday, citing the results of a national study carried out with the Health Ministry.

Among 20- to 24-year-olds, the percentage of men who were overweight jumped to 50.1 percent from 18.5 percent in a survey carried out in 1974, while the percentage of overweight women rose to 48 percent from 28.7 percent.

"We are in a situation of absolute red alert," Brazil's Health Minister Jose Gomes Temporao told reporters in beach-side Rio de Janeiro.

"If we stay at this pace, in 10 years we will have two-third of the population overweight (or obese), as has happened in the United States."

Incomes in Brazil have been rising rapidly in recent years as Latin America's largest country enjoys a prolonged economic boom that has lifted millions out of poverty.

The IBGE did not give reasons for Brazilians' expanding girth but said the biggest incidence was found among higher-income men, older people and in the wealthier south of the country.

"The excess of weight and obesity is a growing phenomenon that is happening everywhere (in Brazil)," said Marcia Quintsler, the IBGE's coordinator. "This information on obesity shows that clearly."

One in three Brazilian children between 5 and 9 years old was above the weight recommended by the World Health Organization, it said.

The IBGE said 49 percent of adult Brazilians were overweight in 2009, based on the body mass index that is calculated from a person's height and weight. That is more than the third of Americans defined as overweight.

The Brazilian obesity rate of 15 percent is still well below the U.S. rate of nearly 27 percent.