The overweight and obesity transition from the wealthy to the poor in low- and middle-income countries: A survey of household data from 103 countries

Abstract

Background

In high-income countries, obesity prevalence (body mass index greater than or equal to 30 kg/m ²) is highest among the poor, while overweight (body mass index greater than or equal to 25 kg/m ²) is prevalent across all wealth groups. In contrast, in low-income countries, the prevalence of overweight and obesity is higher among wealthier individuals than among poorer individuals. We characterize the transition of overweight and obesity from wealthier to poorer populations as countries develop, and project the burden of overweight and obesity among the poor for 103 countries.

Methods and findings

Our sample used 182 Demographic and Health Surveys and World Health Surveys ( n = 2.24 million respondents) from 1995 to 2016. We created a standard wealth index using household assets common among all surveys and linked national wealth by country and year identifiers. We then estimated the changing probability of overweight and obesity across every wealth decile as countries’ per capita gross domestic product (GDP) rises using logistic and linear fixed-effect regression models. We found that obesity rates among the wealthiest decile were relatively stable with increasing national wealth, and the changing gradient was largely due to increasing obesity prevalence among poorer populations (3.5% [95% uncertainty interval: 0.0%–8.3%] to 14.3% [9.7%–19.0%]). Overweight prevalence among the richest (45.0% [35.6%–54.4%]) and the poorest (45.5% [35.9%–55.0%]) were roughly equal in high-income settings. At $8,000 GDP per capita, the adjusted probability of being obese was no longer highest in the richest decile, and the same was true of overweight at $10,000. Above $25,000, individuals in the richest decile were less likely than those in the poorest decile to be obese, and the same was true of overweight at $50,000. We then projected overweight and obesity rates by wealth decile to 2040 for all countries to quantify the expected rise in prevalence in the relatively poor. Our projections indicated that, if past trends continued, the number of people who are poor and overweight will increase in our study countries by a median 84.4% (range 3.54%–383.4%), most prominently in low-income countries. The main limitations of this study included the inclusion of cross-sectional, self-reported data, possible reverse causality of overweight and obesity on wealth, and the lack of physical activity and food price data.

Conclusions

Our findings indicate that as countries develop economically, overweight prevalence increased substantially among the poorest and stayed mostly unchanged among the wealthiest. The relative poor in upper- and lower-middle income countries may have the greatest burden, indicating important planning and targeting needs for national health programs.

Abstract

Tara Templin and colleagues project the burden of obesity in 103 countries.

Author summary

Why was this study done?

• Obesity prevalence has been rising in every country in the world since 1975 and contributes to an increasing proportion of noncommunicable disease risk and burden.

• Within countries, obesity prevalence is highest among wealthier population strata in poorer countries, but the burden of obesity shifts to poorer population strata as national wealth increases.

• While the flipped wealth gradients of obesity in poor and rich countries are documented, no research shows how this shift happens or where it occurs along the range of economic development.

• This work was motivated by a desire to inform policy makers of when and how this reversal is likely to occur, because obesity among the poor has different implications for public health policy than obesity among the wealthy.

What did the researchers do and find?

• We collated 182 Demographic and Health Surveys and World Health Surveys [ n = 2.24 million respondents] from 103 countries with information on respondent height, weight, personal wealth, and country wealth.

• We estimated the relationship of personal wealth with overweight and obesity, and examined how that relationship varies with country wealth.

• At a gross domestic product (GDP) per capita of $8,000, the prevalence of obesity is no longer the highest among those in the top wealth decile ($10,000 for overweight), and at $30,000, obesity prevalence among those in the poorest decile is higher than among the wealthiest ($50,000 for overweight). The transition is driven by increasing obesity among the poor without appreciable decreasing obesity among the wealthy.

• Above $10,000 GDP per capita, the relationship between overweight and personal wealth starts to change as overweight prevalence among those in the lower deciles of wealth increases.

• We estimate that 70.2% (64.1%–76.4%) of countries will begin or have undergone this shift by 2040, and the number of people who are both obese and poor (in the lowest quintile) in our study countries will increase by 17.3 million people (15.3–19.6).

What do these findings mean?

• Distinct points along the obesity transition may represent a particularly effective time for policy makers to implement obesity interventions.

• At a GDP per capita of $8,000, the burden of paying for the costs of obesity may start to increase, as the prevalence of obesity is no longer uniquely concentrated among the wealthy.

• People in the richest decile may not be affected by the same economic mechanisms that increase obesity in the poor, as obesity prevalence of the wealthy within each country does not change substantially with economic development.