Among 80,821 children and adolescents across 26 ethnic minority groups, we found that boys had lower burden of excess body weight, but increased burden of obesity, underweight and severe wasting, compared with girls. The results also indicated a higher prevalence of underweight in boys than that of excess body weight, however, a different result was detected in girls aged 10 to 18 years who showed a higher prevalence of excess body weight than malnourished. The present study additionally revealed that the characteristics of the burden of abnormal nutritional status vary among different ethnic minority groups. It is of great significance to analyze ethnic difference in the burden of excess body weight and underweight, which is helpful to develop policies and interventions for improving the nutrition status in these young populations.
The burden of excess body weight in boys was lower than that of girls, though the prevalence of obesity was higher in boys. Some studies conducted in western countries, such as the United States, Canada, France, Germany, and Italy, have revealed the sex difference and illustrated that boys were more likely to be obese than girls [25, 26]. Although the mechanisms are not fully demonstrated, previous studies showed the risk of being obese differs by sex during puberty periods [27, 28]. Accumulation of fat was more likely to appear in girls after the timing of pubertal onset because of hormone secretion. We found the prevalence of excess body weight and obesity in boys and girls were different before and after the onset of puberty. For example, boys showed higher risks of excess body weight and obesity before 12 years, but lower risks of excess body weight and obesity after 12 years than girls (Table 1). The age of 12 years was the approximate time of puberty in boys and girls. Thus, we speculated that puberty could be the reason why different risks for excess body weight were found between boys and girls before and after 12 years. These variations in fat accumulation could also partly explain why girls had lower prevalence of underweight than boys in this study. A similar finding was found in Han children and adolescents during the same period as well [29, 30]. However, the mechanism has still not been fully demonstrated, and further study is warranted to clarify it.
Our results indicated the burden of excess body weight was higher than that of underweight in minority girls. This results were consistent with that in Han girls, which showed the prevalence of excess body weight and underweight were 14.6% and 8.9%, respectively [7]. Compared with Chinese Han children in other studies using the same definitions [31], the prevalence of excess body weight was lower in Chinese ethnic minorities who additionally showed higher prevalence of underweight across the age groups. Though Chinese children are presenting a faster transition from underweight to excess body weight [32], the speed of shift is higher in Chinese Han than that in ethnic minorities. Thus scientific intervention policy aimed to prevent unhealthy nutritional transition in ethnic minorities is needed. Nutrition improvement interventions in minority areas may have contributed to the declined prevalence of underweight [33]. However, a conflicting result was identified in boys whose burden of excess body weight was lower than that of underweight. Previous studies have demonstrated that the demand of nutrients and calories in boys is higher than that in girls during puberty [28, 29]. As a consequence, if the supply is not adequate, boys are more likely to be malnourished. In addition, China is currently experiencing a transition from a history of underweight to a very rapid increase of obesity [34, 35], and a considerable heterogeneity in the timing of the transition from underweight to excess body weight provides variation in weight change between boys and girls [36, 37]. Therefore, the existence of excess body weight and underweight in ethnic minority children may be not be synchronous in both sexes. As the observation of dual burden of underweight and excess body weight, both problems become major health issues affecting Chinese ethnic minority children and warrant more attention to each issue simultaneously.
The present study revealed different ethnic characteristics by analyzing 26 Chinese minority population groups. The Korean, Mongolian and Kazakh groups with the lowest underweight prevalence were more likely to be obese, which may be related with their dietary behavior. Mongolian and Kazakh are traditional nomadic ethnicities, and they make a living by animal husbandry. Koreans live in the northeast region of China, where the climate is characterized by a winter lasting more than 6 months in duration with the temperature below freezing. As a result, Koreans are typically accustomed to eat a lot of meat to maintain body temperature. Surveys in these minority groups also found that the frequency and amount of meat intake in children and adolescents were much higher than their counterparts of other minorities [33]. The Shui, Bouyei, Li, and Dai children ranked in the top four minority groups for underweight, and had the lowest prevalence of excess body weight. High proportions of severe wasting in underweight were also detected in Li and Dai children, which could be attributed to their relative low socio-economic levels. These four minorities live in southwest undeveloped mountain area with a low standard of living. These results indicated the importance of ethnic-specific policies, and different approaches are warranted to improve the nutritional status among various minorities.
This study showed that Chinese ethnic minority children are facing a dual burden of excess body weight and underweight. Our results have public health implications for policy making and targeted interventions among ethnic minorities. On one hand, both excess body weight and underweight in childhood are associated with adulthood chronic diseases, including diabetes and cardiovascular diseases [38,39,40]. The customized implementation of nutrition improvement program and obesity intervention has a potential to reduce the risk of these chronic disease in minority areas. On the other hand, the ethnic differences in dual burdens among various minorities suggest minority-specific policies are warranted to reduce these burdens effectively. Exploring the influence factors for dual burden in ethnic minority groups could be helpful to find their advantages and disadvantages and further develop a suitable nutrition intervention programs for local minority young population.
This study has a large sample size and involves more than 80,000 ethnic minority children and adolescents. It has strengths for addressing the nutrition problems in these populations. However, several limitations of this study should also be noted. Firstly, there are 55 ethnic minorities in China, but only 26 ethnic minority groups were included in our study. Studies conducted in other minorities are desired to address the health problems among other ethnic minorities. Second, the data of this study were derived from a cross-sectional study, and we did not analyze the risk factors of excess body weight and underweight. However, the epidemiologic characteristics of abnormal nutrition status in this study were developed from the latest available data with large sample size, which could help us to depict the nutrition problems in these minority populations. Third, BMI was used in our results to indicate nutritional status of children, which may do not distinguish between lean and fat mass. Other more precise markers could account for more of the BP trends, like dual energy X-ray absorptiometry and MRI. However, BMI is regarded as the measurement method highly correlated with more precise measures of adiposity and thinness, and it is widely used in epidemiological studies. Other precise markers are not suitable for our surveys with such a large sample size because they are resource intensive measurements.