In the present study, gender, living area, age group, CRP concentration and vitamin A status were associated with children and adolescents with overweight and obesity.
In line with our findings, some systematic reviews have reported on growing prevalence of obesity and overweight among children and adolescents. A meta-analysis concluded that the prevalence of obesity in children and adolescents aged 2 to 19 years in the United States in 2011–2014 was 17.0%, while the prevalence of extreme obesity was 5.8%. A systematic review in Asia, reported that the overall prevalence by gender was 7.0% and 4.8% in boys and girls for obesity in children, and 11.7% and 10.9% in boys and girls respectively for overweight in children. We found that the prevalence of overweight and obesity were 22.9% and 11.2%, respectively, higher than the previous literature. Similarly, we also found that the prevalence among males were higher than females. We found higher prevalence of obesity and overweight in urban areas. Conversely, a study in Bangladesh reported that
overweight and obesity was associated with rural participants. A study of China base on 1995–2014, revealed that overweight and obesity increased in Chinese children and adolescents, particularly in rural areas. Our study was carried out in 2016–2017, whether there is a long-term trend in the distribution of obesity in urban and rural areas still needs to be further studied.
CRP is produced in the liver, macrophages, and adipose tissues. Elevated serum CRP is associated with obesity among children. A study in Japan reported that CRP increased the risk of obesity in school children. Nappo reported that CRP levels are associated to higher body mass and overweight/obesity risk in a large population of European children. Children with higher baseline levels of CRP were at higher risk of developing overweight/obesity during growth.We confirmed that CRP level was higher in obese or overweight than that in non-obese children, as reported in previous studies. The mechanism lies in that obese children present increased oxidative stress and impaired inflammation and insulin sensitivity, which in turn result in similar impaired endothelial dysfunction and early signs of atherosclerosis. Obesity is a pro-inflammatory state that may predispose patients to acute coronary syndrome characterized by chronic low grade inflammation resulting in endothelial dysfunction.Thus, CRP play an important role in the prevention of chronic inflammation associated with obesity in the early stages of life.
Our previous study reported that the prevalence of vitamin A deficiency was 4.5%, and the prevalence of marginal deficiency of vitamin A was 24.7%. At present, the nutritional status of vitamin A is not optimistic. This study found that the retinol level of obese students is higher than that of non obese children, which may be related to the dietary structure of obese children. Liang reported that vitamin A metabolism may be disordered in obese children, although children with obesity have higher vitamin levels than lean children. Gajewska reported that BMI value may influence the vitamin A status in obese children after therapy. Gajewska suggest there is an occurrence of relationships between vitamin A and oxidized LDL in prepubertal obese children. Vitamin A concentrations is associated with dyslipidemia. The relationship and mechanism between obesity and vitamin A should be further explored in the future study.
Shaikh reported that children with high BMI showed extremely high prevalence of vitamin D deficiency. Kang reported that during the coronavirus disease-2019 (COVID-19) pandemic, increased childhood obesity and vitamin D deficiencies were observed. Meta-analysis reported that children and adolescents with obesity have higher risk of vitamin D deficiency[29–30]. Also, A positive association between obesity and lower 25(OH)D serum concentration was found among Chinese adults. Our study found that children and adolescents with obesity had higher concentration of 25(OH)D3, while in the multifactor analysis, vitamin D status was not the influencing factors for children and adolescents with obesity or overweight. The next step of research will further explore the influencing factors of vitamin D status, in order to better explore the relationship between vitamin D and obesity. It is suggested to encourage physical exercise, the reduction of screen time, and healthy eating habits in order to reduce the prevalence of overweight and obesity in children and adolescents and the impact of associated comorbidities, to keep the appropriate micronutrient status.
In China, measurement of serum CRP levels is not included in school health checkups, and it is difficult to obtain informed consent for blood sampling from school children and their parents. Thus, few serological surveys have been performed in healthy children. We performed serological tests in this the China National Nutrition and Health Survey 2016–2017 and evaluated the relationship between the test results and obesity.
Limitations of the present study should be noted. Since it is a cross-sectional study, causality cannot be established. Obesity and micronutrient status may be related to dietary intake and physical activity, which needs to be further explored in future research.