Abstract
Background
Weight misperceptions are common in children and adolescents, which is related to the engagement of weight loss behaviors. The aim of this study was to investigate the association between body weight perception and weight loss behaviors of lower-calorie diets and increased levels of physical activity (PA).
Methods
The Ningbo Youth Risk Behavior Survey was conducted from 2007 to 2022. A multistage, stratified cluster sampling procedure was utilized to draw target adolescents aged 12 to 18 years participating in each survey wave (2007, 2012, 2017, 2022). Data of anthropometry, weight perception, and weight loss behaviors were collected through self-administered questionnaires. A binary generalized linear model was used to examine associations between body weight perception and weight loss behaviors of lower calorie diets and increased levels of PA.
Results
The sample sizes for each survey wave were 777, 885, 1588 and 2638. The prevalence of overweight (OW)/obesity (OB), self-perception of OW/OB and overestimated perception increased from 7.6%, 27.0% and 29.1% in 2007 to 16.3%, 39.9% and 41.4% in 2022, respectively. Adolescents that perceived themselves as OW/OB had higher odds of lower-calorie diets (OR: 4.2, 3.3–5.4) and increased level of PA (OR: 3.8, 2.9-5.0), whereas adolescents that perceived themselves as underweight had lower odds of lower-calorie diets (OR: 0.371, 0.253–0.542) and increased levels of PA (OR: 0.381, 0.295–0.559).
Conclusion
OW, self-perception of OW/OB and overestimated perception were prevalent in Chinese adolescents. Self-perception of OW/OB was positively associated with lower-calorie diets and increased levels of PA. The results can support public health specialists to promote health education of body perception and improve self-esteem in Chinese children and adolescents.
Keywords: Body weight perception, Weight loss behavior, Diets, Physical activity, Overweight, Obesity, Adolescents
Introduction
In the 21st century, overweight (OW) and obesity (OB) epidemics in children and adolescents have become major public health concerns worldwide [1]. Because of the fast-economic boom, and the changes in dietary patterns and lifestyle for the past four decades in China, the prevalence of OW and OB in children and adolescents increased from 1% to 0.1% in 1985 to 13.8% and 9.6% in 2019, respectively [2, 3]. Childhood OB might have short-term effects on a child’s physical and psychological comorbidities, and academic attainment [4, 5], and the long-term effects of childhood OB, most likely, result in a higher chance of OB, chronic diseases, premature death and disability in their adulthood [6, 7].
Body perception plays an important role in an adolescent’s life as it involves attitude, feelings, appearance and preference because adolescence is a particularly dynamic period with changes in all domains of developments [8]. Because of social influences, Chinese adolescents have their cognition and preference of body weight and body shape, which is a muscular shape for men and a slim shape with light body weight for women [9].
Body weight perception is a better indicator of weight loss behaviors in adolescents than actual body weight [10]. A self-evaluation of an individual’s weight as above, below, or at the expected weight/ about the right weight is defined as body weight perception. A recent systematic review concluded that self-perception of OW in adolescents was associated with an increased likelihood of weight loss attempts as well as with healthy and unhealthy weight control strategies [11]. Some studies showed that healthy or OW adolescents with self-perception of OW were suggested to be more likely to engage in weight loss attempts and weight control behaviors of diets and physical activities (PAs) than those with self-perception of about the right weight [12, 13]. Evidence reveals that adolescents perceiving themselves as OW, rather than actual OW, is most likely to have unhealthy weight control behaviors, such as fasting, laxative use and taking diet pills due to a lack of health awareness [14, 15] Moreover, few studies reported no association between body weight perception below the expected weight and weight control behaviors [16].
To our best knowledge, body weight perception and weight loss behaviors have not been well studied in China. The purpose of this study are (1) to examine the trend in the status of body weight perception in adolescents aged 12 to 18 years in Ningbo, Zhejiang Province from 2007 to 2022; (2) to identify the discrepancy between self-perceptive weight status and body weight status; (3) to investigate the association of body weight perception with weight loss behaviors of lower-calorie diets and increased levels of physical activity (PA) in adolescents.
Methods
Study design and study population
The Ningbo Youth Risk Behavior Survey was an ongoing school-based prospective study conducted in Ningbo, Zhejiang Province, China from 2007 to 2022 with 4 repeated surveys by Ningbo Center for Disease Control and Prevention (CDC). A multistage, stratified cluster sampling procedure was utilized to draw the target samples. In the first stage, 3 out of 10 districts (6 urban, 2 urban-rural junction and 2 rural areas) were randomly selected to be representative for urban, urban-rural junction, and rural areas, respectively, on the basis of socio-economic status (SES). In the second stage, all the target schools were randomly selected from 3 districts based on school levels stratified by junior middle school, senior middle school, and academic and vocational high school (2007, 2012 and 2017: 3:1:1 and 2022: 12:6:6). In the third stage, invitations were sent to school principals and school management. With their permission, 2 classes were randomly selected in each school. In the fourth stage, 1022, 1204, 2144 and 2787 students from the selected classes participated in surveys in 2007, 2012, 2017 and 2022, respectively.
The selection criteria for adolescents included in this study were: (1) children who were born in Ningbo or lived in Ningbo for at least one year; (2) aged from 12 years to 18 years; (3) children’s signed consent to participate; (4) written informed consent of the parent or legal guardian for their children’s participation in this study. Adolescents with a disability or an injury affecting the children’s health examination were not eligible to participate in each survey.
The present study was conducted according to the guidelines proposed by Ningbo CDC (No. 202201) and followed the Declaration of Helsinki. Written or verbal informed consent was obtained from all adolescents, their parents or legal guardians and school officials. Verbal consent was witnessed and formally recorded.
Questionnaires
All adolescents were randomly selected to participate in each survey by completing self-administered anonymous questionnaires independently in their classroom with no teachers present, but under the supervision of well-experienced researchers from Ningbo CDC. The self-administered questionnaires were developed based on the US 1991–2015 Youth Risk Behavior Surveillance System and Global School-based Student Health Survey supported by the World Health Organization (WHO). The questionnaires, covering SES, demography, lifestyle, psychological and health aspects were reviewed and approved by experts, and revised after a pilot study [17]. All submitted information was double-checked for quality control by well-experienced researchers. Missing or misreported information was re-collected during the survey. In case of significant discrepancies (e.g. sex, weight and height), adolescents were required to re-answer those questions. For missing information, adolescents were asked to re-complete those question if they were willing.
Assessment of body weight and body weight perception
All adolescents reported their body weight (kg) and height (cm) based on their previous school annual health check. Body mass index (BMI), identifying general OB, was calculated following the formula: weight (kg)/height2 (m2). BMI z-scores were calculated to standardize the BMI value across sex and age groups [18]. Weight status in Chinese adolescents was classified into underweight (UW), normal weight (NW), OW and OB, using sex- and age- specific reference data from WHO [19]. Adolescents were classified as UW (BMI-for-age z-score < -2 standard deviation (SD)), NW (-2 SD ≤ BMI-for-age z-score: < +1 SD), OW (1 SD ≤ BMI-for-age z-score: < +2 SD) and OB (BMI-for-age z-score ≥ + 2 SD) [19].
All adolescents were asked to evaluate their body weight perception by the following question ‘How would you describe your current body weight?’ with 5 options ‘very UW’, ‘slightly UW’, ‘about the right weight/NW’, ‘slightly OW’ and ‘very OW’. Since few adolescents answered ‘very UW’ and ‘very OW’. Adolescents’ self-perceptive body weight was categorized into ‘UW’, ‘about the right weight/NW’ and ‘OW/OB’.
Weight loss behaviors
All adolescents reported their weight loss behaviors for the past 2 years: (1) ‘Did you try to use lower-calorie diets to lose body weight?’; (2) ‘Did you try to increase your PA level to lose body weight?’ The response options to these 2 questions were “No” and “Yes”.
Covariates
Adolescents were asked to report information on demography (sex, age, school type and residence area), and socio-economics status (SES) including the highest degree of maternal and paternal education levels (no education or lower secondary education, secondary education, and higher education), family structure (single-child family: yes or no) and parental marriage (nuclear family or separated/single-parent family). They were also asked to report their sedentary lifestyle on electronic devices each day for the past seven days (no, ≤ 1 h, 2–3 h and ≥ 4 h) and their sleep duration overnight each day.
Statistical analysis
Descriptive analysis was presented as number and percentage for category variables, and mean and SD for continuous variables. The skewness and kurtosis tests were performed to examine the normal distribution for continuous variables based on P-values greater than 0.05. Statistical differences in percentages and mean values across waves were compared by Chi-Square (Χ²) test and ANOVA with Bonferroni correction, respectively.
A binary generalized linear model (GLM) was used to assess associations between both lower-calorie diets and increased levels of PA (dependent variables) and body weight perception (independent variable) through separate models. Associations were investigated via three models: (1) Model 1: crude model; (2) Model 2: adjusting for confounding factors (sex, age and residence area), SES, sedentary lifestyle and sleep duration overnight; (3) Model 3: further adjusting for BMI and year of the wave. Interactions were examined between independent variables and confounding factors. Only significant interactions were retained in Model 3.
Results were considered statistically significant at a two-tailed level of 0.05. Statistical analysis was conducted using the STATA statistical software package version 17 (2021).
Results
Study population and characteristics
In total, 777, 885, 1588 and 2638 adolescents were included in each survey in the present study (Table 1). The differences in the percentages of demography, SES and PA across waves were statistically significant (P < 0.001 for all the category groups) (Table 2). For continuous values, mean sleep duration overnight decreased gradually, while mean anthropometric values including weight, height and BMI increased (P < 0.001), especially for mean values in 2022, which was significantly from those values in 2007.
Table 1.
Recruitment of the study population participating in the school-based prospective study (2007–2022)
| Excluding variables | 2007 | 2012 | 2017 | 2022 |
|---|---|---|---|---|
| Total participating adolescents (n = 1022) | Total participating adolescents (n = 1024) | Total participating adolescents (n = 2144) | Total participating adolescents (n = 2787) | |
| Missing values | ||||
| Demography: age, sex, race, parental education | 1017 | 1010 | 1765 | 2763 |
| Anthropometry | 1015 | 1010 | 1726 | 2727 |
| Others: lifestyle, health status | 788 | 992 | 1709 | 2713 |
| Invalid values | ||||
| Age criteria | 780 | 898 | 1628 | 2686 |
| Anthropometry | 779 | 896 | 1628 | 2685 |
| Others (e.g. sleep duration overnight) | 777 | 885 | 1588 | 2638 |
Table 2.
Adolescents’ characteristics from 2007 to 2012
| 2007 (n = 777) | 2012 (n = 885) | 2017 (n = 1588) | 2022 (n = 2638) | P* | |
|---|---|---|---|---|---|
| n (%) | |||||
| Sex | < 0.001 | ||||
| Boys | 453 (58.3) | 387 (43.7) | 740 (46.6) | 1332 (50.5) | |
| Girls | 324 (41.7) | 498 (56.3) | 848 (53.4) | 1306 (49.5) | |
| Age (years) | < 0.001 | ||||
| 12–14 | 217 (27.9) | 175 (19.8) | 588 (37.0) | 1019 (38.6) | |
| 15–18 | 560 (72.1) | 710 (80.2) | 1000 (63.0) | 1619 (61.4) | |
| School type | 0.005 | ||||
| Junior middle school | 426 (54.8) | 466 (52.7) | 799 (50.3) | 1273 (48.3) | |
| Senior middle school | 351 (45.2) | 419 (47.3) | 789 (49.7) | 1365 (51.7) | |
| Area of residence | < 0.001 | ||||
| Urban | 177 (22.8) | 281 (31.8) | 577 (36.3) | 907 (34.4) | |
| Urban-rural junction/rural areas | 600 (77.2) | 604 (68.2) | 1011 (63.7) | 1731 (65.6) | |
| Single-child family | < 0.001 | ||||
| Yes | 530 (68.2) | 598 (67.6) | 1008 (63.5) | 1213 (46.0) | |
| No | 247 (31.8) | 287 (32.4) | 580 (36.5) | 1425 (54.0) | |
| Paternal education | < 0.001 | ||||
| No education or lower secondary education | 492 (63.3) | 517 (58.4) | 1266 (79.7) | 2165 (82.1) | |
| Secondary education | 198 (25.5) | 218 (24.6) | 295 (18.6) | 431 (16.3) | |
| Higher education (college or above degree) | 87 (11.2) | 150 (17.0) | 27 (1.7) | 42 (1.6) | |
| Maternal education | < 0.001 | ||||
| No education or lower secondary education | 550 (70.8) | 599 (67.7) | 1308 (82.4) | 2154 (81.7) | |
| Secondary education | 176 (22.7) | 170 (19.2) | 257 (16.2) | 450 (17.1) | |
| Higher education (college or above degree) | 51 (6.6) | 116 (13.1) | 23 (1.5) | 34 (1.3) | |
| Parental marriage | < 0.001 | ||||
| Nuclear family | 718 (92.4) | 799 (90.3) | 1445 (91.0) | 2347 (89.0) | |
| Separated/Single-parent family | 59 (7.6) | 86 (9.7) | 143 (9.0) | 291 (11.0) | |
| Screen-based sedentary lifestyle (hours/day) | < 0.001 | ||||
| No | 280 (36.0) | 408 (46.1) | 784 (49.4) | 1423 (53.9) | |
| ≤ 1 | 329 (42.3) | 312 (35.3) | 557 (35.1) | 794 (30.1) | |
| 2–3 | 126 (16.2) | 128 (14.) | 187 (11.8) | 311 (11.8) | |
| ≥ 4 | 42 (5.4) | 37 (4.2) | 60 (3.8) | 110 (4.12) | |
| Mean (SD) | |||||
| Sleep duration overnight (hours/day) | 8.4 (1.1) | 8.3 (1.3) | 8.2 (1.4) | 7.9 (1.2) | < 0.001 |
| Weight (kg) | 52.8 (10.3) | 52.0 (9.0) | 54.3 (10.5)ab | 56.7 (12.4)abc | < 0.001 |
| Height (cm) | 164.7 (8.5) | 164.6 (8.3) | 166.3 (8.6)ab | 166.7 (8.6)ab | < 0.001 |
| BMI (kg/m2) | 19.3 (2.8) | 19.1 (2.7) | 19.6 (3.1)b | 20.3 (3.7)abc | < 0.001 |
BMI: body mass index; SD: standard deviation
* The chi-square test was used to examine the difference for category groups across 4 waves. One way ANOVA was used to examine the difference for continuous variables across 4 waves.
a mean values were significantly different from 2007 by one way ANOVA WITH Bonferroni POSTHOC
b mean values were significantly different from 2012 by one way ANOVA WITH Bonferroni POSTHOC
c mean values were significantly different from 2017 by one way ANOVA WITH Bonferroni POSTHOC
Distribution of body weight status and body weight perception
The distribution of body weight status and body weight perception were presented in Table 3. The trend in body weight status was significant across waves (P < 0.001). The prevalence of UW in 2007 was 8.0% but decreased to 6.4% in 2022, while the prevalence of OW/OB in 2007 was 7.6% increasing twofold in 2022 to 16.3%. On one hand, the prevalence of self-perception of UW decreased from 30.4% in 2007 to 20.6% in 2022. On the other hand, the prevalence of self-perception of OW/OB increased from 27.0 to 39.9% across 15 years.
Table 3.
Distribution of body weight status and self-perceptive weight stratified by sex and age in adolescents from 2007 to 2022
| 2007 | 2012 | 2017 | 2022 | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Body weight status | |||||||||||||||||||
| UW | NW | OW/OB | P | UW | NW | OW/OB | P | UW | NW | OW/OB | P | UW | NW | OW/OB | P | ||||
| Total | 62 (8.0) | 656 (84.4) | 59 (7.6) | 87 (9.8) | 741 (83.7) | 57 (6.4) | 109 (6.9) | 1318 (83.0) | 161 (10.1) | 169 (6.4) | 2040 (77.3) | 429 (16.3) | |||||||
| Sex | 0.001 | 0.057 | 0.001 | < 0.001 | |||||||||||||||
| Boys | 35 (7.7) | 370 (81.7) | 48 (10.6) | 46 (11.9) | 311 (80.4) | 30 (7.8) | 63 (8.5) | 570 (77.0) | 107 (14.5) | 103 (7.7) | 961 (72.2) | 268 (20.1) | |||||||
| Girls | 27 (8.3) | 286 (88.3) | 11 (3.4) | 41 (8.2) | 430 (86.4) | 27 (5.4) | 46 (5.4) | 748 (88.2) | 54 (6.4) | 66 (5.1) | 1079 (82.6) | 161 (12.3) | |||||||
| Age (years) | 0.01 | 0.063 | 0.001 | 0.039 | |||||||||||||||
| 12–14 | 22 (10.1) | 170 (78.3) | 25 (11.5) | 18 (10.3) | 139 (79.4) | 18 (10.3) | 35 (5.9) | 467 (79.4) | 86 (14.6) | 80 (7.8) | 768 (75.4) | 171 (16.8) | |||||||
| 15–18 | 40 (7.1) | 486 (86.8) | 34 (6.1) | 69 (9.7) | 602 (84.8) | 39 (5.5) | 74 (7.4) | 851 (85.1) | 75 (7.5) | 89 (5.5) | 1272 (78.6) | 258 (15.9) | |||||||
| Self-perceptive weight | |||||||||||||||||||
| UW | NW | OW/OB | P | UW | NW | OW/OB | P | UW | NW | OW/OB | P | UW | NW | OW/OB | P | ||||
| Total | 236 (30.4) | 331 (42.6) | 210 (27.0) | 252 (28.5) | 380 (42.9) | 253 (28.6) | 373 (23.5) | 671 (42.3) | 544 (34.3) | 543 (20.6) | 1042 (39.5) | 1053 (39.9) | |||||||
| Sex | < 0.001 | < 0.001 | < 0.001 | < 0.001 | |||||||||||||||
| Boys | 171 (37.8) | 188 (41.5) | 94 (20.8) | 144 (37.2) | 162 (41.9) | 81 (20.9) | 226 (30.5) | 326 (44.1) | 188 (25.4) | 374 (28.1) | 553 (41.5) | 405 (30.4) | |||||||
| Girls | 65 (20.1) | 143 (44.1) | 116 (35.8) | 108 (21.7) | 218 (43.8) | 172 (34.5) | 147 (17.3) | 345 (40.7) | 356 (42.0) | 169 (12.9) | 489 (37.4) | 648 (49.6) | |||||||
| Age (years) | 0.110 | 0.02 | 0.42 | 0.01 | |||||||||||||||
| 12–14 | 72 (33.2) | 98 (45.2) | 47 (21.7) | 65 37.14 | 66 (37.7) | 44 (25.1) | 133 (22.6) | 261 (44.4) | 240 (24.0) | 229 (22.5) | 419 (41.1) | 371 (36.4) | |||||||
| 15–18 | 164 (29.3) | 233 (41.6) | 163 (29.1) | 187 26.34 | 314 (44.2) | 209 (29.4) | 194 (33.0) | 410 (41.0) | 350 (35.0) | 314 (19.4) | 623 (38.5) | 682 (42.1) | |||||||
UW: underweight; NW: normal weight; OW: overweight; OB: obesity
The chi-square test was used to examine the difference in distribution of body weight status and body weight perception by sex and age for each survey wave
Stratified by sex and age, the trend in body weight status was significant in each wave, with the exceptions of 2007 and 2012 for age groups. Compared with 2007, 2012 and 2017, more girls (49.6%) and older individuals (42.1%) perceived themselves as OW/ OB in 2022. Whereas a great proportion of boys (37.8%) and younger individuals (33.2%) perceived themselves as UW in 2007, compared to the other 3 waves.
The agreement between body weight perception and body weight status in adolescents
Around 45.0% of all adolescents in 2007, 2012 and 2017 and 41.2% in 2022 kept consistently matching their BMI category of NW (Fig. 1). The trend in the proportion of self-perception of OW/OB increased from 2007 (29.1%) to 2022 (41.4%), whereas the proportion of self-perception of UW had a decreasing trend from 25.2% in 2007 to 17.4% in 2022. A greater proportion of boys underestimated their body weight (boys: 24.6-33.1% and girls: 10.0-17.1%) and more girls overestimated their body weight in each wave (boys: 22.7-31.9% and girls: 37.3-51.0%). Although no difference in self-perceptive weight status was found between age groups in each wave except for 2017 based on their body weight, the trend in self-perception of OW/OB across waves was gradually increasing in both age groups.
Fig. 1.
Consistency of body weight status and self-perceptive body weight status in adolescents by sex and age
Distribution of weight loss behaviors stratified by body weight status and body weight perception
The trends in lower-calorie diets and increased levels of PA for weight loss according to the BMI categories and self-perceptive weight were significantly different across waves (Table 4). More adolescents having NW or perceiving themselves as OW/OB had weight loss behaviors of lower-calorie diets and increased levels of PA across the four waves. In 2022, a greater proportion of adolescents perceiving themselves as OW/OB used lower-calorie diets (68.3%) and increased levels of PA (56.3%) for weight loss compared to those in 2007, 2012 and 2017. In addition, an increase in weight loss behaviors of lower-calorie diets and increased levels of PA was observed in adolescents with OW/OB status from 2007 to 2022.
Table 4.
Distribution of weight loss behavior by body weight status and self-perceptive weight from 2007 to 2022
| Variables | 2007 | 2012 | 2017 | 2022 | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Lower-calorie diets | |||||||||||||||
| No | Yes | P | No | Yes | P | No | Yes | P | No | Yes | P | ||||
| BMI categories | 0.004 | < 0.001 | < 0.001 | < 0.001 | |||||||||||
| UW | 61 (9.1) | 1 (0.95) | 74 (10.5) | 13 (7.2) | 100 (8.6) | 9 (2.1) | 156 (8.1) | 13 (1.8) | |||||||
| NW | 565 (84.1) | 91 (86.7) | 600 (85.2) | 141 (77.9) | 961 (82.9) | 357 (83.2) | 1525 (79.3) | 515 (72.0) | |||||||
| OW/OB | 46 (6.9) | 13 (12.4) | 30 (4.3) | 27 (14.9) | 98 (8.5) | 63 (14.7) | 242 (12.6) | 187 (26.2) | |||||||
| Self-perceptive weight | < 0.001 | < 0.001 | < 0.001 | < 0.001 | |||||||||||
| UW | 187 (26.2) | 7 (6.7) | 236 (33.5) | 16 (8.8) | 333 (28.7) | 40 (9.3) | 510 (26.5) | 33 (4.6) | |||||||
| About the right weight/NW | 292 (43.5) | 39 (37.1) | 316 (44.9) | 64 (35.4) | 536 (46.3) | 135 (31.5) | 848 (44.1) | 194 (27.1) | |||||||
| OW/OB | 151 (22.5) | 59 (56.2) | 152 (21.6) | 101 (55.8) | 290 (25.0) | 254 (59.2) | 565 (29.4) | 488 (68.3) | |||||||
| Increased levels of physical activity | |||||||||||||||
| No | Yes | P | No | Yes | P | No | Yes | P | No | Yes | P | ||||
| BMI categories | < 0.001 | < 0.001 | < 0.001 | < 0.001 | |||||||||||
| UW | 61 (11.1) | 1 (0.44) | 65 (11.8) | 22 (6.6) | 87 (10.9) | 22 (2.8) | 134 (9.6) | 35 (2.8) | |||||||
| NW | 460 (83.9) | 196 (85.6) | 468 (84.6) | 273 (82.2) | 661 (83.1) | 657 (82.9) | 1137 (81.2) | 903 (72.9) | |||||||
| OW/OB | 27 (4.9) | 32 (14.0) | 20 (3.6) | 37 (11.1) | 47 (5.9) | 114 (14.4) | 129 (9.2) | 300 (24.2) | |||||||
| Self-perceptive weight | < 0.001 | < 0.001 | < 0.001 | < 0.001 | |||||||||||
| UW | 218 (39.8) | 18 (7.9) | 204 (36.9) | 48 (14.5) | 284 (35.7) | 89 (11.2) | 436 (31.1) | 107 (8.6) | |||||||
| About the right weight/NW | 242 (44.2) | 89 (38.9) | 254 (45.9) | 126 (38.0) | 345 (43.4) | 326 (41.1) | 608 (43.4) | 434 (35.1) | |||||||
| OW/OB | 88 (16.1) | 122 (53.3) | 95 (17.2) | 158 (47.6) | 166 (20.9) | 378 (47.7) | 356 (25.4) | 697 (56.3) | |||||||
BMI: body mass index; UW: underweight; NW: normal weight; OW: overweight; OB: obesity
The chi-square test was used to examine the difference in distribution of weight loss behavior by body weight status and self-perceptive weight for each survey wave
Association between weight loss behaviors and body weight perception
The results showed that self-perception of UW and OW/OB were associated with both lower calorie diets and increased levels of PA in Model 1 (Table 5). After controlling for confounding factors, SES, sedentary lifestyle and sleep duration overnight, self-perception of UW and OW/OB remained significantly associated with both lower calorie diets and increased levels of PA in Model 2. Further controlled for BMI, wave and interactions, associations of self-perceptive weight status in Model 3 maintained significance with both lower calorie diets (UW: OR = 0.371, 95%CI 0.253–0.542; OW/OB: OR = 4.2, 95%CI 3.3–5.4) and increased levels of PA (UW: OR = 0.381, 95%CI 0.259–0.559; OW/OB: OR = 3.8, 95%CI 2.9-5.0). Regarding sex and age, both factors in Model 3 were associated with both lower calorie diets and increased levels of PA. Girls (diets: OR = 2.8, 95%CI 2.2–3.5) and adolescents at 15–18 years (diets: OR = 1.2, 95%CI 0.968,-1.4; PA: OR = 9.6, 95%CI 4.0-22.6) were more likely to engage in weight loss behaviors of lower calorie diets and increased levels of PA.
Table 5.
Associations between self-perceptive weight and weight loss behaviors in adolescents from 2007 to 2022
| Self-perceptive weight status | Lower-calorie diets | |||||||
|---|---|---|---|---|---|---|---|---|
| Model 1 | Model 2 | Model 3 | ||||||
| OR | 95% CI | OR | 95% CI | OR | 95% CI | |||
| About the right weight/normal weight | 1 | 1 | 1 | |||||
| Underweight | 0.338 | 0.268, 0.427 | 0.369 | 0.292, 0.467 | 0.371 | 0.253, 0.542 | ||
| Overweight/Obesity | 3.6 | 3.1,4.1 | 3.3 | 2.9, 3.8 | 4.2 | 3.3, 5.4 | ||
| Increased levels of physical activity | ||||||||
| OR | 95% CI | OR | 95% CI | OR | 95% CI | |||
| About the right weight/normal weight | 1 | 1 | 1 | |||||
| Underweight | 0.341 | 0.291, 0.399 | 0.343 | 0.293, 0.402 | 0.381 | 0.259, 0.559 | ||
| Overweight/Obesity | 2.9 | 2.5, 3.2 | 2.8 | 2.5, 3.2 | 3.8 | 2.9, 5.0 | ||
OR: odds ratio; CI: confidence interval
A binary GLM was used to investigate the associations. Model 1: crude model; Model 2: adjusting for sex, age and residence area, socio-economic status, sedentary lifestyle and sleep duration overnight; Model 3: further adjusting for BMI, year of the wave and significant interactions
Discussion
The purpose of this representative study was to investigate the association between self-perceptive weight and dietary and PA weight loss behaviors in adolescents aged 12–18 years from 2007 to 2022 with four repeated surveys. Our results indicated that self-perception of UW and self-perception of OW/OB were associated with lower and higher odds, respectively, of both lower calorie diets and increased levels of PA.
The trend in the prevalence of OW/OB in adolescents increased gradually across the four waves. On the contrary, the prevalence of UW showed a decreasing trend, which was supported by a recent review [20]. Interestingly, according to adolescents’ body weight status in our study, the prevalence of misperception increased in 2022 compared to the other 3 waves with a decrease in underestimation and an increase in overestimation. Over half of the adolescents in each wave failed to perceive their weight adequately with a higher proportion of overestimation than underestimation. Similar results from Chinese cross-sectional studies were reported in adolescents in Zhejiang Province (45.4% misperception) with 9.9% underestimation and 35.5% overestimation and nationwide adolescents (39.2% misperception) with 30.0% underestimation and 9.2% overestimation [13, 21]. This is compared to cross-sectional studies from two other countries which reported weight perception in Brazilian adolescents with 39.6% perceiving themselves to be above the expected weight and 29.3% perceiving themselves to be below the expected weight, and 47.5% misperception in South Korean adolescents with 23.5% underestimation and 24.0% overestimation [16, 22]. In line with one previous cross-sectional study conducted in children and adolescents in Zhejiang Province, we noticed that relatively higher proportions of girls and older individuals (15–18 years) perceived themselves as OW or overestimated perception compared to their peers [21]. Therefore, the status of body weight perception reflected adolescents’ concerns about body weight and body shape. This might be attributable to the leanness and muscularity culture accepted by adolescents during the dynamic period with changes in cognition, physiology and psychology. This phenomenon is influenced by mass media and Westernization as well [8].
With an increasing trend in overestimated perception and a decreasing trend in underestimated perception in adolescents from 2007 to 2022, our study examined the trend in weight loss behaviors by weight status and weight perception status. It is noteworthy that the prevalence of weight loss behaviors in adolescents with OW/OB BMI category and self-perception of OW/OB by lower calorie diets and increased levels of PA rose in 2022 compared to the waves in 2007, 2012 and 2017. Although no longitudinal studies have investigated on weight loss behaviors in Chinese adolescents, our results were in line with previous cohorts from other countries [23, 24].
Regarding the associations between self-perceptive weight and weight loss behaviors, our findings are consistent with some reports from previous cross-sectional studies conducted on weight loss attempts in adolescents by both diets and PA [21, 25], only diets [13, 22] or PA [26, 27]. Results from a school-based survey in 2017 including 17359 children and adolescents in Zhejiang Province indicated that self-perception of OW was positively associated with weight control behaviors including exercise, diets and fasting [21]. That report supports our findings which reflect the current weight loss behaviors in school-aged children in China.
Some literature showed divergent findings that overestimated perception, in particular, higher BMI or OW adolescents were more likely to have unhealthy lifestyles and dietary intakes with less PA [25, 28], due to insufficient health awareness and knowledge of weight management attempts [29]. A previous cross-sectional study conducted on American adolescents (12–17 years) revealed that adolescents perceiving themselves as OW were less likely to engage in healthy habits such as PA or healthy eating [28]. Supported by 2-year longitudinal data including 19322 secondary school students in Canada, a report suggested that OW perceptions discourage PA and healthy dietary practices, while weight perceptions of NW appeared to favor healthier dietary patterns and PA behaviors in both boys and girls [25]. One possible reason for the divergent findings is that we did not collect information on patterns of diets and PA during weight loss. Adolescents with self-perception of OW used extreme weight loss behaviors which might reflect their psychological status due to social influence and school-fellow discrimination [21, 30]. Evidence showed that the adolescents with overestimated perception and self-perception of OW have strong intentions to lose weight using unhealthy behaviors including fasting, pills and vomiting [27, 31, 32]. Moreover, weight perception of OW/OB is considered to be strongly associated with adverse consequences of psychological effects, which resulted in undesirable behaviors [33]. Therefore, studies on the attitudes and patterns of weight loss behaviors in adolescents need to be further examined.
Notably, UW perception has not gained sufficient research attention. In our study, self-perception of UW was negatively associated with both lower-calorie diets and increased levels of PA compared to self-perception of NW, which was in line with one previous study [21]. With the limited available research reports, those results indicated that self-perception of UW was positively associated with unhealthy weight loss behaviors including taking pills, laxatives and fasting [21, 31]. Nevertheless, it was concluded that adolescents having self-perception of UW had less motivation for weight management behaviors with less engagement in PA and more unhealthy dietary behaviors as they are more likely to consider themselves to have excellent health [25, 28]. Our findings have important implications to improve body weight perceptions and reduce misperceptions of body weight for better understanding on how body weight perceptions affect weight control behaviors in Chinese adolescents. In addition, our findings can assist public health specialists for school-based public health campaigns to improve awareness on health, well-being and psychology including self-esteem, self-respect, and self-love.
Furthermore, weight loss behaviors vary in sex and age. Although both boys and girls increasingly overestimating their weight across waves caused the attempts of weight loss in our study [23], girls were associated with higher odds of both lower-calorie diets and increased levels of PA and adolescents in the older age group were associated with increased levels of PA. With body growth, psychological impacts and social influence, adolescents have different motivations for building body shape. Weight-gain attempts through PA and high-quality protein consumption are more common in boys and have become increasingly prevalent in adolescents older than 15 years since it is the top priority for muscular shape [23], whereas, girls increase the level of PA along with lower-calorie diets for losing body weight and building a slim body shape since they feel guilty about having energy-dense diets or no PA.
The key strength of this study was the long-term study with 4 repeated surveys covering SES, demography, lifestyle, psychological and health aspects. Our findings can contribute to the limited evidence of associations of weight loss behaviors with body weight perception in Chinese adolescents. Despite this strength, this study has several limitations. Firstly, self-reported body weight and height collected through self-administrated questionnaires relied on adolescents’ memory and psychological bias, which might affect the accuracy of actual BMI status, and the agreement of weight perception and actual weight status. Secondly, we did not collect the patterns of diets and PA, and so we cannot precisely present the patterns of unhealthy weight loss behaviors. Therefore, future research should carry out a longitudinal study to examine the association of weight perception with the patterns of weight management behaviors.
Conclusion
Self-perception of OW/OB was associated with higher odds of both lower-calorie diets and increased levels of PA, in girls and older adolescents in particular. Our findings could assist in supporting public health specialists to promote school-based health education programmes to improve healthy body image perception and establish self-esteem and self-confidence.
Acknowledgements
All authors thank all staff for their great field work. In addition, we thank all students to participate in this study.
Abbreviations
- BMI
Body mass index
- CDC
Center for Disease Control and Prevention
- GLM
Generalized linear model
- NW
Normal weight
- OB
Obesity
- OW
Overweight
- PA
Physical activity
- SD
Standard deviation
- SES
Socio-economic status
- UW
Underweight
- WHO
World Health Organization
Author contributions
HQG was in charge of funding acquisition and supervision. YL performed methodology, formal analysis and drafted manuscript writing. RR contributed to writing – review & editing. SXL, XYL, SJW and WWL was responsible for project administration.
Funding
This study was supported by Ningbo Science and Technology Plan Project (NO. 2022S077), Natural Science Foundation of Zhejiang Province (No. LTGY24H260007) and Ningbo Top Medical and Health Research Program (No.2023020713).
Data availability
The dataset will be available upon the request to the corresponding author.
Declarations
Ethics approval and consent to participate
The present study was conducted according to the guidelines proposed by Ningbo CDC and followed the Declaration of Helsinki. Written or verbal informed consent was obtained from all adolescents, their parents or legal guardians and school officials. Verbal consent was witnessed and formally recorded.
Consent for publication
Not applicable.
Competing interests
The authors declare no competing interests.
Footnotes
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Contributor Information
Yi Lin, Email: Lily.Lin@nottingham.edu.cn.
Qing-Hai Gong, Email: gongqinghai@163.com.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The dataset will be available upon the request to the corresponding author.