A large number of studies have shown that overweight and obese children are more likely to become obese adolescents and adults, with major short and long-term health and economic consequences. Findings from the present analysis indicated that the prevalence of overweight and obesity were 15.25 and 11.95% respectively. The overall overweight and obesity prevalence is similar to those well-developed countries [19], but is higher than those reported in previous studies in China and other Asia countries [3, 5]. Together with the current findings, a fast rise in the prevalence of overweight and obesity, in China children has been revealed within a very short period of time, which is alarming. From 2017 to 2021, the obesity and overweight prevalence rise of Chinese children and adolescents had a slight downward trend and practically remained at a stable level [20, 21]. However, the overall prevalence is still at high level and long-term trend needs to be observed. Furthermore, the huge population of obese and overweight children and adolescents still needs more attention. The burden of overnutrition among adolescents is expected to escalate without effective interventions, and its associated consequences would manifest soon.
The overweight and obesity prevalence had region-, age- and sex-specific characteristics. Consist with previous studies, boys and children in urban region in Hangzhou had higher prevalence of overweight and obesity [22, 23]. The detection rate of overweight and obesity among children and adolescents in urban areas are higher than those in suburban counties, which may be related to the fact that urban children and adolescents are more likely to obtain unhealthy lifestyle factors (e.g., electronic products -viewing duration, physical/sedentary activity) and dietary factors (e.g., electronic products -viewing duration, physical/sedentary activity). On the other hand, adolescents in rural areas may be involved in household chores, including farm works during non-school hours, and may need to walk to schools often for longer distances, making them more physically active [24]. Multivariate analysis found that overweight and obesity prevalence in girls was lower than that in boys. It may be related to the fact that boys consume more food and eating faster than girls, prefer meat and high-energy foods. Moreover, due to the influence of traditional aesthetic concepts, girls pay more attention to body management than boys [24]. Furthermore, Our findings also corroborated a lower prevalence of overweight and obesity among boarding students. Mechanistically, compared to day students, boarding students have long sedentary duration, less accessible puffed foods and sugary drinks, and less greasy diets.
As for the difference between different ages, we found that the overweight prevalence increased significantly after the age of eight, while it was reduced when reaching the age of 17 years old, and the obesity prevalence increased between the ages of 8–10, but then continued to reduced. The age difference in weight gain might be related to the growth characteristics and lifestyles of children of different ages. Furthermore, the overweight and obesity prevalence in primary school students was higher than that in junior and senior high school students, which is consistent with the relevant domestic research results [25, 26]. It is suggested that primary school is the key stage for the prevention and control of overweight and obesity in children and adolescents. It may be related to the weaker health awareness of primary school students, the more significant increase in height than weight after middle school students enter puberty [27], and the higher tolerance of obesity in primary school students in traditional concepts. Furthermore, students who already have menstruation or nocturnal emission have an increased risk of overweight and obesity, which may be related to the changes of hormone levels around puberty.
At present, the proportion of children and adolescents drinking sugar-sweetened beverages in China is as high as 66.6% [28], which has becoming the largest consumer group of sugar-sweetened beverages. Studies have shown that excessive intake of sugar-sweetened beverages will have a certain impact on human health, especially increasing the risk of overweight and obesity [29]. However, present study did not find an association between sugar-sweetened beverages or sweets and overweight/obesity, which may be caused by some of the student questionnaires were filled out by their parents, does not reflect the actual situation. Consumption of vegetables and fruits is generally believed to be a protective factor for overweight and obesity, as both are considered to be low-energy-density foods, and the dietary fiber they contain reduces the intake of energy-dense foods [30]. The results of this study did not find an association between vegetable and fruit intake and overweight and obesity, which could be caused by this study is only based on the frequency of fruits and vegetables intake, and cannot effectively determine the energy generated after fruit intake.
Inadequate physical activity and intake of less healthy diet are well-established risk factors of overweight and obesity. Given that physical activity and dietary behaviors has been nonsignificantly associated with overweight and obesity in present study, which similar to Li's findings [31], we speculate that the imprecision in the measurement of diet and physical activity due to recall bias and the inadequacy of the questionnaire to assess these behaviors may be some reasons for the findings. No association was found between relative risk of overweight and substance abuse such as smoking, drinking and illicit drugs in present study. Bullying victimization associated with increased risk of overweight and obesity, Smith’s studies also came to the same conclusion [32]. on the one hand, bullied students may be less likely to participate in physical activity. On the other hand, obese students are also more likely to be bullied because of poor body size and athleticism [33]. Our research found that high blood pressure increased the risk of overweight and obesity, yet many studies show that overweight and obesity are independently associated with incident hypertension in a Chinese population [34–36]. Currently, the effect of hypertension on overweight and obesity is not very clear, and the mechanism of the interaction between them needs to be further explored.
In conclusion, the overweight and obesity prevalence among children and adolescents in Hangzhou is still at a relatively high level, and is affected by most factors such as high blood pressure, had menstruation or nocturnal emission, eating fresh fruit frequency, school period and gender. Our findings emphasize the need for using these risk factors to help develop effective strategies for reducing the childhood obesity burden in China.