Being overweight or obese is one of the most important social and health problems, and its prevalence is increasing continuously worldwide, including in China[4, 23, 24]. Currently, it is generally believed that lifestyle and diet are the primary causes of being overweight or suffering from obesity[6, 25], and that the future solution for such epidemiological issues should come from political policies based on prevention of those aspects related to health and social customs surrounding being overweight or obese. However, not enough is yet known about these factors, which furthermore may vary from place to place[7, 26]. In this study, we systematically analyzed the differences in dietary patterns and the prevalence of being overweight or obese between the South and North of China. The prevalence of being overweight or obese in the South was 10.51% less than that of the North, with this prevalence falling when moving through regions from Northern areas to Southern areas. Moreover, the Southerners’ dietary score regarding the quality of food consumed was also lower by 1.1% than that of Northerners. People in the North have a high intake of wheat, tubers, fruits, etc., whereas individuals in the South eat more rice, vegetables, meat, poultry, etc. From the South to the North, all of these estimated coefficients regarding dietary patterns and being overweight or obese were positively and significantly correlated with the geographical variable. In addition, with the spatial span increase defined by three regional types from the South to the North (neighboring provinces, South–Central–North areas, and South–North areas), the estimated coefficients for dietary score increased from 0.287 to 1.494, the OR for being overweight rose from 0.923 to 1.681, and the OR for obesity increased from 0.902 to 2.035. Finally, after placing regional variables and the two dietary patterns extracted using factor analysis into the same model, the OR of the three variables for being overweight were statistically significant at 1.464, 1.223 and 1.242, respectively, but only the OR of Northern dietary patterns and regional type III for obesity were statistically significant at 1.697 and 1.199, respectively. In short, residents from the South were also less likely to be overweight or obese than those from the North before and after adjustment for individual socio-demographic characteristics and household factors[5].
Firstly, there are significant differences in dietary patterns between the North and South of China. One plausible contributor is regional differences in the geographical environment. China has a natural, geographical dividing line—the Qinling–Huaihe Line, which consists of the Qinling Mountains and Huaihe River—which leads to differences between the North and South in many respects[8]. This natural dividing line is also a dividing line in terms of climate. In the North, there is a temperate monsoon climate with little rainfall. In contrast, in the South, there is subtropical monsoon climate with plenty of rain[27]. Owing to the difference in climate between the North and South, the residents’ farming methods are also different. Residents in the North mainly cultivate drought-tolerant crops, such as wheat, whereas residents in the South primarily grow subtropical cash crops, including rice and tea[28]. As a result, over the course of history, residents have established a variety of dietary cultures with local geographic characteristics, and the types of local agricultural products available may be responsible for some of the differences in dietary patterns[29]. For example, wheat became a main staple food in the North, and rice a major staple in the South. The present study’s findings are consistent with the actual geographical and cultural characteristics of China as well as findings of previous works[9]. Furthermore, we applied factor analysis to extract two dietary patterns that roughly represent the difference in dietary characteristics between the North and South; these extracted dietary patterns also show that Southern dietary patterns are rich in rice, vegetables, meat, and poultry, whereas Northern dietary patterns are rich in wheat, soybeans, etc. A number of studies have established that the “modern high-wheat” pattern is rich in fat and induces a high risk of obesity and metabolic syndromes, whereas “vegetable-rich” and “healthy patterns” have had no associations with metabolic syndromes[10, 30]. Zhang’s work showed that traditional Southern dietary patterns feature a high intake of vegetables, fish, and meat, or what constitutes a balanced dietary pattern that may help to reduce the risk of chronic diseases, such as abdominal obesity and hypertension[31]. In addition, climate conditions may contribute to the differences in nutritional intake. The North is colder than the South, and as such, Northerners need to take in more energy to resist the cold, so their total food consumption is more than that in the South[32]. Meanwhile, Southern residents usually eat coarse fiber foods, such as corn and buckwheat, which can easily enhance a sense of satiety and control the amount of energy consumed[9, 33]. As a result, the differences in dietary patterns may be contributed to the geographical differences in climate and culture.
Secondly, the odds of being overweight or obese change rapidly and with positive significance as the geographic variables moving from South to North. When the region variable sequentially moves from one province to another across all 11 provinces from the Southern areas to the Northern areas, the prevalence of being overweight or obese slowly rises, but it increases quite quickly when the region variable directly moves from the Southern to the Northern areas. These phenomena and positive estimated coefficients indicated that the prevalence of being overweight or obese is significantly correlation with regional variables. This may also be explained by differences in physical activity[6, 34, 35]. The difference between energy intake and output partial contributed by physical activity means that rates of being overweight or obese are higher in the North than in the South[5]. Another reasonable contributing factor may be dietary patterns. The present findings indicate that Chinese residents established local characteristics of lifestyle and diet cultures throughout long-term historical activities because of the existence of a boundary line between the North and South, which further affects residents’ dietary patterns. Overall, differences in residents’ rates of being overweight or obese may derive from characteristics of the long-established culture or lifestyle as impacted by an individual’s residence, features of the dietary culture, and the regions themselves; persons in the North have greater eating scores and are more overweight or obese than those in the South. Swinburn and Egger have outlined an ecological framework for understanding rates of being overweight or obese, and they distinguished specific types of environments, including physical, economic, and socio-cultural environments[36, 37]. Hawkins and Griffiths found that the United States’s geography affects early childhood rates of being overweight through dependence after adjustment for individual socio-demographic characteristics[38]. Angela also demonstrated that pre-adolescent children in Germany are considered overweight with marked geographical differences in prevalence[39]. Regions with unique environmental, cultural, or policy-related (e.g., infrastructure) traits may provide or support opportunities for physical activity and/or access to a healthy diet, which have different influences on the prevalence of being overweight or obese.
Based on the geographical differences and dietary habits formed throughout its long history, there are certain dietary and cultural differences between Northern and Southern China. However, the differences may not only be seen in contemporary residents, but also their elders, and the present study determined that Northern elderly residents have higher rates of being overweight or obese and dietary scores than those of Southern elders. The rates of fathers and mothers being overweight or obese in the North are 19.66% and 18.81% higher than those in the South, respectively, and the dietary scores of those in the North are 1.72 and 0.88 points higher than those in the South, respectively. Furthermore, parents’ rates of obesity had a positive and significant correlation with participants’ rates of being overweight or obese, and parents’ dietary scores were also significantly correlated with participants’ dietary scores. This difference and this correlation indicate that geographical differences may have a significant impact on dietary patterns for each generation, and local dietary patterns and geographical differences further affect residents’ nutritional balance[40, 41]. Furthermore, residents’ household income, age, education level, and sedentary time also exerted some influence on the prevalence of being overweight or obese. Persons with higher household income, age, and sedentary time were more likely to be obese, but those with higher education levels were less prone to obesity[42–44]. Currently, with the rapid increasingly economy and concomitant changes in lifestyle, there has been a markedly high intake of fast foods in China[45]. However, because most fast foods have high fat and energy levels, thus leading a greater risk of hypertension, glucose, and being overweight or obese[46]. It is necessary to be aware of the problems of rapidly changing dietary patterns and obesity-related diseases.
The present research has several strengths compared to other studies. We selected 11 representative provinces to demarcate the differences in dietary patterns and rates of being overweight or obese between the North and South of China, and for the first time, we studied the causes of these differences in an empirical manner considering geographical differences and dietary patterns, specifically taking into account traditional Chinese culture[9, 47]. In addition, we comprehensively described specific dietary patterns of residents from the North and South while comparing the differences in the dietary structure of residents by the method of DBI, which could serve as a robust predictor of being overweight or obese and lead to effective policy interventions. Furthermore, the study provides information regarding the relationships among the South–North geographical difference, dietary patterns, and the prevalence of being overweight or obese. Northerners in the study ate differently from Southerners, at least from a qualitative perspective, probably consuming more food and leading to more opportunities for obesity. Finally, based on the natural geographical dividing lines in China, we discussed the historical origin of the differences in residents’ dietary patterns and the causes of the differences in rates of being overweight or obese, combining the characteristics of an individual’s living environment and traditional culture. Our results also suggest that a series of relevant policies should be put in place to support the improvement of dietary patterns and living habits, thereby removing barriers to healthy eating and nutritional balance.
Several limitations of this study did exist. We did not specifically evaluate the factors of economic status, family environment, physical activity, education level, registration, smoking, drinking, or genetic factors, and simply accounted for them as control variables in this paper. Further work is necessary to consider differences in the surrounding environment between the North and South to determine how these differences may promote a healthier nutritional balance. In addition, because of the limited information on nutrition, we did not assess the differences in nutritional composition between Northerners and Southerners. Certainly, there are other factors that may cause differences in the problems of being overweight or obese.