American kids aren’t the only ones being couch potatoes these days, according to new study of more than 70,000 young teens from 34 countries.

From Argentina to Zambia, Regina Guthold of the World Health Organization in Geneva and her colleagues found, most kids aren’t getting enough exercise, while nearly a third are sedentary.

And while thoughts of the “third world” may bring to mind long walks to school and heavy physical labor for children, this isn’t what Guthold and her team found. “With regards to physical activity levels, we did not find much of a difference between poor and rich countries,” the researcher told Reuters Health via email. “Growing up in a poor country does not necessarily mean that kids get more physical activity.” Guthold noted.

In their study, published in The Journal of Pediatrics, Guthold and her team looked at 72,845 13- to 15-year-old schoolchildren from North and South America, Asia, Europe, and the Middle East. The children were surveyed between 2003 and 2007.

The researchers defined adequate physical activity as at least an hour of exercise (outside of gym class) at least five days a week. Children who spent three or more hours watching TV, playing computer games, or chatting with friends (aside from time in school or time spent doing homework) were classified as sedentary.

Just one-quarter of the boys and 15 percent of the girls were getting enough exercise by their definition, the researchers found. And a quarter of boys and nearly 30 percent of girls were sedentary and didn’t get enough exercise.

In every country, aside from Zambia, girls were less active than boys. In more than half of the countries in the study, less than a quarter of the boys were getting enough exercise.

Uruguay had the highest percentage of active boys, at 42 percent, while Zambia had the lowest, at 8 percent. Girls from India were the most active, with 37 percent meeting exercise recommendations, while girls from Egypt were the least active, with just 4 percent getting adequate exercise.

Kids in Myanmar were the least sedentary, with 13 percent of boys and 8 percent of girls classified as sedentary; the most sedentary nations were St. Lucia and the Cayman Islands, with 58 percent of boys and 64 percent of girls spending at least three hours a day in sedentary activity.

While the study didn’t look at the reasons behind the lack of physical activity in various nations, Guthold speculated that urbanization could be a factor, as could the near-universal availability of cars and TVs.

Schools can help children become more active by having physical education classes and educating students about the importance of exercise, the researcher said. Adding lanes for bicycles, pedestrian crossings and other changes to promote walking and biking to and from school could help too, she added, as could giving kids space to be active wherever they live.

Studying physical activity in entire populations is difficult, Guthold noted, and any questionnaire used to measure physical activity will have limitations.

However, “even with the limitations that questionnaire data (suffer) from, I guess it’s pretty safe to say that we have a huge problem with physical inactivity among schoolchildren around the globe and that we should take action,” she concluded.

SOURCE: The Journal of Pediatrics, online March 22, 2010.