Introduction

Adolescence, typically spanning from ages 10 to 19, represents a critical transitional period between childhood and adulthood [1]. It is a time of intense physical, psychological, and social development, laying the foundation for lifelong health and well-being [2]. However, alarming trends in childhood obesity have raised significant concerns regarding the health of adolescents. According to estimates by the World Obesity Federation, 206 million children and adolescents with obesity aged 5 − 19 years in 2025, and 254 million in 2030 [3]. Similarly, the Report on Nutrition and Chronic Diseases in China (2020) revealed that nearly 20% of Chinese children and adolescents with overweight or obesity aged 6 to 17, with boys exhibiting higher rates than girls [4]. Adolescent obesity, particularly during puberty, has been linked to a host of physical and mental health issues, including depression [5] and cardiovascular disease [6].

The association between physical health and lifestyle behaviors, particularly dietary habits and exercise, is well established [7]. Unhealthy eating behaviors may lead to energy imbalance and obesity. In China, snacking has become a prevalent dietary habit among children and adolescents [8]. Snacking refers to the consumption of food and drink outside of meal times, and is a growing area of concern in public health. While snacking can provide an additional source of energy, the impact on body weight needs to be considered in terms of frequency, portion size, and type of snacking consumed [7, 9]. Studies have demonstrated that high consumption of ultra-processed foods is strongly linked to adolescent and adult obesity [10, 11], oral health problems [12], and an increased risk of cardiovascular disease [13]. Furthermore, a diet high in ultra-processed foods may increase the risk of non-communicable diseases, while unprocessed or coarse processed foods may reduce the risk [14]. Therefore, interventions aimed at improving snack choices could prove effective in addressing the public health challenge of obesity [15].

Body image is a complex, multidimensional construct that encompasses an individual's self-perception and sensory experiences of their body, including their estimation of body size and attitudes toward their physical appearance [16]. Body weight misperception refers to the discrepancy between an individual's perceived weight and their actual weight [17]. Research has established a clear association between body weight misperception and eating behavior [18]. Perception of weight influences adolescents' lifestyle behaviors [19], including their eating habits and mental health outcomes [20]. For example, adolescents who overestimated their weight status are more likely to take behaviors for managing their weight compared to those who accurately perceive their weight status [21]. Notably, there was also a correlation between weight perception and high-calorie snacking behavior [22], with study indicating that adolescents who misperceive their weight tend to consume more snacks [17].

The majority of research on adolescent weight has concentrated on the association between snacking behavior and weight outcomes [23, 24]. However, the impact of weight perception on snacking intake, especially snacking patterns among Chinese adolescents, remains poorly understood. Thus, the aim of this study was to examine the association between body weight misperception and snacking patterns among school adolescents.

Methods

Study Design and Sample Collection

This cross-sectional study was conducted between December 2, 2021, and December 15, 2021, using the online survey platform “Questionnaire Star”. With the support of the Chongqing Municipal Education Commission, we adopted the convenient sampling method and selected 310 junior middle schools in 41 districts and counties of Chongqing as the survey sites. The questionnaire link or QR code was sent to the WeChat work groups of these schools. The teacher in charge forwarded the instructions and questionnaire to the parents through WeChat group of grades 7, 8, and 9. With the informed consent of parents and students, students filled in the questionnaire anonymously and independently on weekends or at home after school.

In total, 190,296 questionnaires from grades 7, 8, and 9 were included for analysis after excluding 11,855 outliers and missing data. This study was approved by the Ethics Committee of Chongqing Medical University. The informed consent form was at the beginning of the questionnaire, and the respondents gave their informed consent before they started to fill in the questionnaire.

Body weight misperception definition

Body weight and height measurements were self-reported. The four body mass index (BMI) categories of normal, underweight, overweight and obese were derived by using the ‘zbmicat’ STATA function, which uses age- and gender-adjusted BMI cut-offs from the International Obesity Taskforce (IOTF) [25]. Based on the survey data from Brazil, Great Britain, Hong Kong, the Netherlands, Singapore, and the United States, the percentile corresponding to a child's BMI curve passing through the adult cut-offs points at age 18, i.e. BMI of 18.50, 25.00 and 30.00 kg/m2, is defined as the cut-offs for underweight, overweight and obesity of different ages and sex from 2 to 18 years old [26]. Weight perception was assessed by the question “How would you rate your weight? (1- underweight, 2- normal weight, 3- overweight/obese)”. Body weight misperception was assessed by comparing participants' actual weight status to their self-perceived weight status. Students' self-perceived weight status was categorized as underestimation (self-perceived weight was lower than true BMI classification), correct (self-perceived weight equaled to true BMI classification) and overestimation (self-perceived weight was higher than true BMI classification).

Snack intake assessment

Intake of snacks was collected using a qualitative food frequency questionnaire (FFQ) based on China Children and Youth Snacks Guide [27]. The FFQ was revised by epidemiologists, statisticians, nutrition, and child health experts to ensure the validity and reliability of the questionnaire content, and has been validated in Chinese children [30]. It should be noted that, due to the presence of snack items with negative factor loadings, the scores could potentially be < 0. Consequently, each child was assigned a score for each snacking pattern, where higher scores indicated a stronger correspondence with the snacking pattern.

The relationship between body weight misperception and snacking patterns (pattern scores) was examined using multiple linear regression models. Model 1 adjusted for age, and model 2 further adjusted for sex, ethnicity, grade, accommodation, residence, an only child, primary guardians, and parents’ education. In the subgroup analyses, the multiplicative interaction between body weight misperception and covariates (sex, ethnicity, grade, accommodation, residence, the only child, primary guardians, and parents’ education) was examined by adding the product of the variables in the regression model.

All statistical analyses and data management were performed in STATA/MP (version 17.0 College Station, TX, USA). A two-tailed p-values < 0.05 were considered statistically significant for all analyses.

Results

Sample description

A total of 190,296 students from Chongqing were surveyed and included in the analysis. Table 1 presents the demographic characteristics of the sample, which had an average age of 13.3 ± 1.0 years, with a nearly equal proportion of males and females (50.2% vs. 49.8%). The majority of students were in grade 7 (35.6%) with fewer in grade 8 (32.5%) and grade 9 (31.9%), and most were Han Chinese (95.8%). The majority of students lived in urban areas (57.4%) and 44.6% were in school accommodation. Their parents' education level was mostly junior high school (fathers: 64.6%; mothers: 66.0%). The majority were not the only child in their family (76.7%), and the primary guardians were parents (68.0%), grandparents (10.2%), mixed (14.2%), and others (7.5%). The proportion of students categorized as normal, underweight, overweight/obese was 71.3%, 10.5%, 18.2%, respectively.

Table 1 Basic demographic characteristics based on actual BMI categories
Full size table

Body weight misperception by actual BMI categories and sex

The misperception of body weight across different actual BMI categories and sex are illustrated in Fig. 1. The findings reveal a higher prevalence of weight overestimation among students compared to weight underestimation (30.0% vs. 14.5%). Notably, a significant proportion of underweight students (44.8%) tended to overestimate their weight. Among students with a normal weight, more than half (50.6%) demonstrated weight misperception, with 35.5% overestimating and 15.1% underestimating their weight. In contrast, students categorized as overweight or obese displayed a lower likelihood of weight misperception, with only 20.3% underestimating their weight. Furthermore, the rate of weight misperception was found to be lower among boys compared to girls (39.1% vs. 50.0%). Boys exhibited a higher rate of underestimating their weight (22.2%), whereas girls had a higher rate of overestimating their weight (43.3%).

Fig. 1
figure 1

Comparison of body weight misperception by actual BMI categories and sex

Full size image

Snacking patterns identifying

Two snacking patterns were extracted by factor analysis named (1) high-calorie snacking pattern (characterized by high intake of potato chips and French fries; fried meat skewers; odd taste beans and marinated bean curd; high-sugar drinks; puffed food, cream cake, chocolate pie, and spicy gluten; sugar-coated nuts; hawthorn juice, iced tea, and Yakult; condensed milk; marshmallow, milk candy, fruit candy, and chocolate, etc.) and (2) healthy snacking pattern (characterized by high intake of boiled corn, unsweetened oats, and whole wheat bread; soybean milk and roasted soybeans; peanuts, melon seeds, and other nuts; fresh milk and yogurt; freshly squeezed fruit and vegetable juice; fresh fruits and vegetables; poached eggs; roasted sweet potatoes, steamed mashed potatoes, etc.). The two snacking patterns explained 39.6% and 18.8% of the snack intake variances respectively. Snack items at absolute factor loadings of ≥ 0.40 are shown in Table 2.

Table 2  Snacking patterns and component loadings extracted by factor analysis
Full size table

Association between body weight misperception and two snacking pattern scores

The results of the multiple linear regression are shown in Table 3. Following adjustment for potential covariates, weight underestimation was positively associated with high-calorie snacking pattern scores among normal weight students (β: 0.16, 95% CI: 0.11, 0.21) and students with overweight/obesity (β: 0.44, 95% CI: 0.35, 0.52), and was positively associated with healthy snacking pattern scores among students with overweight/obesity (β: 0.28, 95% CI: 0.22, 0.33), but was negatively associated with healthy snacking pattern scores among normal weight students (β: -0.12, 95% CI: -0.15, -0.09). Additionally, weight overestimation was negatively associated with high-calorie snacking pattern scores and healthy snacking pattern scores among normal weight students (β: -0.07, 95% CI: -0.11, -0.04 and β: -0.13, 95% CI: -0.15, -0.10), but was positively associated with healthy snacking pattern scores among underweight students (β: 0.15, 95% CI: 0.08, 0.21).

Table 3  Multiple linear regression analysis of associations between body weight misperception and snacking patterns
Full size table

Subgroup analyses

There were significant interactions between weight misperception and sociodemographic factors (sex, grade, accommodation, only child, primary guardians, parental education level) in relation to snacking patterns. Notably, there was an interaction between sex and weight misperception in relation to both snacking patterns. The association between underestimation of weight and high-calorie snacking pattern was stronger among females than males. The inverse association between overestimation of weight and both snacking patterns was only significant among females but not males (Table 4).

Table 4 Subgroup analyses of associations between body weight misperception and sociodemographic factors in relation to snacking patterns
Full size table

Discussion

In this study, we explored snacking patterns and their association with body weight misperception in a sample of junior middle school students in Chongqing, China. Two snacking patterns were identified, named high-calorie snacking pattern and healthy snacking pattern. Our results revealed that almost half of the students in our sample misperceived their weight status, with overestimation of weight status being more prevalent than underestimation. This may be due to the aesthetic concept of thinness as beauty, leading many young people to focus on their body shape under social pressure to conform to the idea of thinness [31]. The weight misperception rate in our study was slightly higher than those reported among young adults in Pakistan (42.4%) [32], Mexico (36.9%) [33], Ghana (20.6%) [34], and among adolescents in Korea (34.1%) [35] and Spain (23.5%) [36], but similar to the study among adults in Guangdong, China (50.2%) [40].

Interestingly, our research also found that students categorized as overweight or obese represented a lower likelihood of weight misperception, with only 20.3% underestimating their weight. We surmise the tendency to overestimate weight can explain this phenomenon. Due to the social condemnation and media influence on people with overweight/obesity, few of them think that they is thin or normal, and weight misperception in people with overweight/obesity have only one option: underestimation. In addition, body weight misperceptions, including both underestimation and overestimation, could result in incorrect behaviors about weight control and eating [31]. Weight misperception, in particular overestimation, was related to psychological outcomes such as stress [40]. Therefore, programs and comprehensive interventions on correcting adolescent weight misperceptions to establish correct body image perceptions are necessary for the physical and mental health of teenagers. A contrary to commonly held thoughts study show weight misperception among youth who were overweight or obese predicted lower future weight gain. Thus, we should rigorously examine the efficacy of efforts to correct weight misperception to assess for both intended and unintended consequences [41].

It has been shown that adolescents' actual BMI status affects their self-reported weight and the associated weighting behavior, so different actual BMI classifications were considered in our analysis [42]. Incorrect perceptions of body weight have been linked to both healthy and unhealthy dieting behaviors [35, 43]. And our study revealed that compared to students who correctly perceived their weight, students with normal weight who underestimated their weight were more inclined to the high-calorie snacking pattern. Our findings are consistent with prior research that has reported an association between overestimating body weight and unhealthy snacking behaviors in adolescents [40, 44, 45], which can increase the risk of overweight and obesity. Adolescents with overweight or obesity who underestimated their weight prefer both of the snacking patterns above, indicating that those who misperceived their weight consumed more snacks, regardless of the snack type [46]. A study conducted in Indonesia similarly found that adolescent girls who underestimated their weight were 2.7 times more likely to consume deep-fried crackers compared to those who correctly assessed their weight [19]. But a study of 7–12 years old children in Guangzhou, China, reported that among overweight children, those who accurately perceived their weight had a higher intake of fruits and vegetables than those who underestimated their weight [47]. This difference may be attributed to the fact that the outcome variable in our study was the snacking pattern, which took into account the consumption of other types of crude processed foods, whereas the outcome variable in the Guangzhou study was only the intake of fruits and vegetables.

Meanwhile, many studies have identified the misperception of being with overweight or obesity among adolescents at normal weight as a risk factor for eating behavior disturbances [48, 49]. A study of Iranian children also showed that in comparison with the accurate-weight group, the overestimated-weight groups were less likely to have a daily consumption of sugar-sweetened beverages, sweets, and salty snacks [50]. Although snacking less may help to reduce the risk of obesity, the sequence of weight misperception, body dissatisfaction, and dieting (especially of healthy foods like vegetables, fruits, and milk) may lead to negative eating attitudes, which could increase the risk of various pathologies, including anxiety/depression, psychological distress symptoms, anorexia, and malnutrition [18, 49,

Conclusion

In conclusion, our study found that nearly half of the students misperceived their weight status and overestimation of weight status was more prevalent than underestimation. Adolescents with normal weight and overweight/obesity who misperceived their weight exhibited less healthy snacking patterns, whereas underweight students who misperceived their weight displayed healthier snacking patterns. Furthermore, there were significant interaction between sex, grade, accommodation, only child, primary guardians, parental education level and body weight misperception. To address this, it is important for families, schools, and society to implement comprehensive programs to help adolescents understand their weight status and guide them to make healthier snack choices. Those who underestimate their weight should be encouraged to reduce high-calorie snacks and focus on weight management, while those who overestimate their weight should eat more nutritious snacks instead of avoiding snacks altogether. This will reduce the risk of obesity, chronic diseases in the former, and anorexia and wasting in the latter.