NEW YORK - Although "first-world" health problems like obesity and heart disease are gaining ground in developing nations, a new study finds they are mostly afflicting the rich and middle class while poor people remain undernourished and underweight.
Over the past decade, researchers have warned that excess fat and related health problems, like diabetes and heart disease, are a growing problem in lower-income nations -- prompting calls to launch a global fight against obesity and the chronic diseases linked to it.
One recent study, for example, found that rates of abdominal obesity, high blood pressure and diabetes rose steadily in a group of young, urban adults in India who were followed for seven years.
India, a country of 1 billion-plus, was projected to account for 60 per cent of the world's heart disease cases in 2010. Another recent study found that people in India and other South Asian countries suffer their first heart attack at age 53, on average -- six years earlier than the rest of the world.
There has also, however, been a large social divide noted within developing nations -- with wealthier, better-educated people becoming heavier while the poor stay thin, sometimes dangerously so.
To see whether that gap might be narrowing, researchers on the new study looked at body mass index (BMI) among more than 547,000 women from 37 low- and mid-income countries in Asia, Africa and South America.
Just over 200,000 women were interviewed and weighed between 1991 and 2003, while the rest were studied between 1998 and 2008.
In most countries, the percentage of overweight and obese women rose each year. But there was a clear divide between the better-off and the poor, the researchers found.
Across countries, the wealthier women were, the higher their average BMI, a measure of weight in relation to height. And that pattern showed no change over time.
While even poor women showed an increase in the number who were overweight, they still lagged far behind their wealthier counterparts. Across the countries, 18 per cent of the poorest women (the bottom 20 per cent by income) were overweight during the second survey period. That compared with 45 per cent of the wealthiest women.
Essentially, "the poor stay thinner," the researchers report in the American Journal of Clinical Nutrition.
"I don't want to minimize the problem of obesity," said senior researcher S.V. Subramanian, a professor of population health and geography at Harvard University in Boston.
However, he said in an interview, in the midst of the worries over weight gain in the developing world, "we need to bring more data into the discussion."
"Yes, on average, people are getting heavier in these countries," Subramanian said. "But who is getting heavier?"
"A huge amount of the population is still undernourished," he said.
That, according to Subramanian, means many countries in the world need two opposite public health efforts: one to encourage wealthier people to curb their calorie intake, and one to get more food to the people who need it.
The pattern is different from that seen in wealthy countries, like the US, where lower incomes and less education often correlate with a higher number on the bathroom scale. (That's at least true among women, Subramanian noted. With men, income and education have not been clearly linked to obesity risk.)
In many poorer nations, though, food remains expensive. And the most impoverished citizens, Subramanian and his colleagues write, simply can't afford to boost their calorie intake.
For the time being, Subramanian said, the problems of obesity and its related ills seem to be largely concentrated among wealthier people in the developing world. And a "balance" of policies -- to fight obesity on one hand, and fight hunger on the other -- is still needed.