A new study from the Harvard School of Public Health (HSPH) finds that high body mass index (BMI身体质量指数) in developing countries remains primarily a problem of the rich. The findings suggest that the shift towards overweight and obesity among the poor that has already happened in wealthier countries has not yet happened in developing countries. The study appears in an advance online edition of the American Journal of Clinical Nutrition and will appear in an upcoming print edition.

"Previous research on the increasing overweight and obesity burden in developing countries has assumed that the burden is shared by everybody within these countries; however, we found that the social patterning of weight continues to closely resemble the unequal distribution of income and other resources," said S V Subramanian, lead author of the paper and associate professor in the department of society, human development, and health at HSPH.

Subramanian and his colleagues analyzed data from nationally representative samples of 538,140 women ages 15 to 49 drawn from Demographic and Health Surveys conducted in 54 low- to middle-income countries between 1994 and 2008. They looked at BMI, education, household wealth, and the per capita Gross Domestic Product (pcGDP) from the women's home countries. The researchers found an association between BMI and wealth in every country except Moldova and Kazakhstan. Globally, a 25% increase on the measure of wealth index was associated with a 54% increase in BMI and a 33% increase in overweight. Similar patterns were observed in urban and rural areas within countries. There were no strong associations found between weight and either education or pcGDP.

The researchers theorize that these findings could be due to a number of factors, including that women in higher income groups are more likely to have diets richer in animal fats than lower-income women. Also, cultural norms in developing countries may favor fatty body shapes among wealthier women. Richer women are also less likely than poor women to engage in regular physical labor.

While increasing BMI and overweight prevalence（流行，普遍） are important public health concerns in many of these countries, their distribution among socioeconomic groups needs to be a central consideration in drafting policies for improving the nutritional status of populations in developing countries, according to the researchers.

"Our findings have serious policy implications," Subramanian said. "If being overweight is primarily concentrated among the rich, should precious public resources be targeted to reducing overweight or should they be devoted to policies that improve nutritional outcomes among the poor?" He added, "The fact that the burden of overweight and underweight（重量不足） is concentrated largely in two distinct socioeconomic groups actually is a good thing from a policy perspective, with the challenge being how to balance the emphasis in terms of priorities."