Research Shows Older Children, Adolescents Grew Heavier In Brazil, China, U.S. Over Past 30 Years

Between 1991 and 1997, the percentage of overweight children climbed 20 percent in China but dropped by almost half in Russia, which fell on economic hard times.

The UNC study is the first to use similar data to compare changes in weight among children in those nations, which contain about a third of the world's population, authors said. It underscores the global significance of health-damaging weight gain among a sizeable percentage of youth.

"This work shows the burden of nutritional problems is shifting from energy deficiencies to energy excesses among many children in countries like Brazil and China," said lead author Dr. Youfa Wang. "Changes like this pose a major challenge for lower income countries, which in some cases face a growing double burden -- both obesity and poor nutrition. We believe nutrition programs for children and adolescents around the world should be revised to consider these rapidly emerging concerns."

A report on the findings appears in the June issue of the American Journal of Clinical Nutrition. Besides Wang, now assistant professor of human nutrition, epidemiology and biostatistics at the University of Illinois at Chicago, authors are Drs. Carlos Monteiro, professor of nutrition at the University of Sao Paulo, Brazil, and Barry Popkin, professor of nutrition at the UNC School of Public Health and a fellow at the Carolina Population Center.

"We used nationally representative survey data from these four nations collected over the past several decades with a new international standard for measuring child and adolescent obesity," Popkin said. "We attempted to fill a gap by exploring trends in the shift from underweight to overweight among older children ages 6 to 9 and adolescents ages 10 to 18."

Between 1971 and 1997, excessive weight tripled as a percentage of all children and teens in Brazil, from 4.1 percent to 13.9 percent, and almost doubled in the U.S., from 15.4 percent to 25.6 percent, Wang said. It increased by a fifth in China from 6.4 percent to 7.7 percent between 1991 and 1997. In contrast, in Russia, it fell from 15.6 percent to 9 percent between 1992 and 1998 during tremendous economic stress and a large reduction in the energy density of the diet.

Overweight prevalence was considerably higher in older children than in adolescents in Brazil, China and Russia but not in the U.S., he said. Also, during the survey periods, the underweight prevalence decreased in Brazil from 14.8 percent to 8.6 percent, in China from 14.5 percent to 13.1 percent and in the U.S. from 5.1 percent to 3.3 percent. The percentage of poorly nourished Russian children climbed from 6.9 percent to 8.1 percent.

Better economic conditions, except in Russia, appear to have spurred the weight gains, Wang said. Other factors were increasingly secure food supplies with more nutrients and higher energy densities, easier access to transportation, more leisure time and growing physical inactivity.

Previous studies documented the increases in excessive weight among adults, and recently, two comprehensive investigations examined obesity in preschool children from developing countries, he said. None, however, has addressed the issue among older children and adolescents internationally, and that's why researchers did the study.

"People have noted the large increase in child and adolescent obesity in the United States and Europe or tiny samples in a few other countries, but no one has had large representative samples in other parts of the world," Popkin said. "Also, most studies have used outmoded standards that were inconsistent between each survey.

"During a time when diabetes and other signs of heart disease are emerging among children around the world, these shifts in varying environments and socioeconomic conditions are most troubling," he said.