Abstract
OBJECTIVE:
To explore the factors associated with the sex disparity showing a greater prevalence of obesity/overweight in boys compared with girls in Chinese school children.
METHODS:
Sampled students and their parents were asked to complete a questionnaire. Perceptions of weight status by the parents, grandparents and children themselves were collected. A logistic regression analysis was used.
RESULTS:
The sampled students included 327 obese/overweight students and 1078 students with normal body mass index (BMI). The crude OR of obesity/overweight for boys compared with girls was 1.57 (95% CI 1.22 to 2.01). The increased risk of childhood obesity/overweight for boys remained after adjustment for prenatal and infant factors, daily habits and family situation, but disappeared after adjustment for perception of weight status (OR 1.27 [95% CI 0.93 to 1.67]). There were differences in underestimation of children’s weight status between boys and girls by their parents and grandparents (OR 1.33 [95% CI 1.08 to 1.64] and OR 1.42 [95% CI 1.15 to 1.75], respectively).
CONCLUSIONS:
Misconceptions about a child’s weight status were prevalent among parents and grandparents, and boys’ weight status was more frequently underestimated than girls. The disparity of underestimating weight according to sex may partially contribute to the difference in the prevalence of obesity/overweight between boys and girls among Chinese school children.
Keywords: Children, Obesity, Overweight, Perception, Prevalence, Sex
Abstract
OBJECTIF :
Explorer les facteurs associés à l’écart entre les sexes qui démontrent une plus grande prévalence d’obésité et d’embonpoint chez les écoliers que chez les écolières en Chine.
MÉTHODOLOGIE :
Les chercheurs ont invité un échantillon d’élèves et leurs parents à remplir un questionnaire. Ils ont colligé les perceptions des parents, des grands-parents et des enfants. Ils ont utilisé une analyse de régression logistique.
RÉSULTATS :
L’échantillon se composait de 327 élèves obèses ou faisant de l’embonpoint et de 1 078 élèves à l’indice de masse corporelle (IMC) normal. Par rapport aux filles, le rapport de cotes brut d’obésité et d’embonpoint pour les garçons était de 1,57 (95 % IC 1,22 à 2,01). Le risque accru d’obésité ou d’embonpoint juvénile des garçons était maintenu après rajustement compte tenu de facteurs liés à la prénatalité et au nourrisson, aux habitudes quotidiennes et à la situation familiale, mais disparaissait après rajustement compte tenu de la perception du poids (RC 1,27 [95 % IC 0,93 à 1,67]). Les parents et les grands-parents sous-estimaient le poids des garçons et des filles de manière différente (RC 1,33 [95 % IC 1,08 à 1,64] et RR 1,42 [95 % IC 1,15 à 1,75], respectivement).
CONCLUSIONS :
L’évaluation erronée du poids d’un enfant est prévalente chez les parents et les grands-parents, le poids des garçons étant plus sous-estimé que celui des filles. L’écart de sous-estimation du poids entre les sexes peut contribuer à la différence de prévalence d’embonpoint ou d’obésité chez les écoliers et écolières en Chine.
Over the past several decades, there has been overwhelming epidemiological evidence that childhood obesity is increasing. This is becoming a key public health issue in both industrialized and developing countries (1–3). In some countries and races, the prevalence of obesity is higher among women than among men (4,5). Sex differences in childhood obesity are not as consistent as those observed among adults. Studies from India, the United Kingdom and Ireland have documented a greater prevalence of obesity in girls than in boys (6–8), while some studies from Australia, the United States and Finland have reported the opposite (9–12). In China, the prevalence of obesity is greater among women than men. In contrast, during childhood, the prevalence of obesity is greater in boys compared with girls (13).
Hormone production and activity do not appear to exhibit sex-related differences before sexual maturity (14). Several sociodemographic and family environment characteristics, such as prenatal practice, socioeconomic situation and parenting behaviour, have been found to be associated with the risk of obesity/overweight among Chinese children (15–17). However, the potential role of sex differences in obese Chinese children has not been well explored.
According to Chinese cultural tradition, overweight is not regarded negatively but, rather, is viewed as good health. Elderly people prefer larger infants and regard overweight boys as stronger individuals. Considering that children are cared for by parents, we hypothesized that the sex disparity in childhood obesity/overweight is related to family factors and cultural practice. We were particularly interested in evaluating whether the perception of child’s weight status by parents and grandparents differed between boys and girls, which may have a potential impact on the magnitude of the sex disparity.
METHODS
A cross-sectional survey and a two-stage cluster sampling design were used to assess the parent’s perception of their child’s weight. First, two primary schools were randomly selected from each of the five districts in Changsha City, Hunan, China. Then, one class from grades 4, 5 and 6 in each school was selected. Height and weight measurements were obtained from the annual physical examination. The measuring instruments were the same type (TGZ-50, Changzhou Wujin Scale Company, China), were calibrated, and the measurements were obtained by the same researchers. The selected children removed their shoes before measurements. Exclusion criteria included secondary obesity, which refers to obesity due to endocrine or other systemic disease, digestive system diseases, metabolic diseases, cardiovascular diseases, endocrine diseases, severe rickets and children experiencing puberty changes. Obesity, overweight, underweight and normal weight was defined using the body mass index (BMI) cut-off values for sex and age established in 2009 by the Department of Growth and Development of the Capital Paediatrics Institute in China (18). This national reference was used rather than WHO or Centers for Disease Control and Prevention (Georgia, USA) references to provide norms that were more representative of the local population. The sex-specific BMI ≥85th percentile for age was defined as overweight, ≥95th percentile as obese and ≤5th percentile as underweight. The survey was performed during the annual physical examination. The selected students were asked to complete a questionnaire after the physical examination. The data collected from the children included lifestyle factors (eg, exercise, diet and sleep). The parents were also requested to complete a questionnaire, which was brought to them by their children. The questionnaires completed by the parents were collected the following day. A few questionnaires were not completed in time and participants were asked to return them the next day. Data collected from the parents included family medical history, family income, pregnancy and birth experiences (eg, birth weight, mode of delivery) and prenatal practice, which was defined as pregnant women playing favourable musical tapes or using an earphone and other devices attached to their abdomen after 26 weeks of pregnancy for at least 15 min/day, and infant feeding. The factors listed in the questionnaire were chosen based on a combination of literature review and previous hypotheses. Perceptions of weight status (whether the child was perceived as obese, overweight, under-weight or normal weight) by parents, grandparents and children themselves were included in the questionnaires. The perceptions of a child’s weight status were compared with the actual weight status determined by the BMI cut-off values. Underestimation meant that obese, overweight and normal-weight children were perceived as overweight, normal-weight and underweight, respectively. Both actual sex disparity and perception-related sex disparity regarding weight status were assessed. The questionnaire was pretested by students from a fourth-grade class and their parents, and was found to be acceptable. This enabled the revision of any difficult items in the questionnaire. The Institutional Review Board of the Central South University (Hunan, China) approved the study. Informed written consent was obtained from the parents of each student.
Demographic characteristics, family factors and cultural practice were first compared between obese/overweight and normal children using a χ2 test. Then, the statistically significant factors from univariate analyses were subjected to multiple logistic regression models as independent variables, with weight status as the dependent variable (obesity/overweight = 1, normal BMI = 0). A forward stepwise procedure was used in the logistic regression to select significant factors, in which α (in) = 0. 10 and α (out) = 0. 15. The frequency of underestimation of weight for boys and girls by their parents and grandparents was also compared. All analyses were performed using SPSS version 15.0 (IBM Corporation, USA). Written informed consent was obtained with the questionnaire.
RESULTS
There were 1637 students from 30 different classes. Thirty-one students did not participate for various reasons. Questionnaires were distributed to 1606 school children. Of 1606 questionnaires, 1425 questionnaires were found to be valid, corresponding to a response rate of 89%. There were 20 underweight children (nine boys and 11 girls) among 1425 children. Because the sample was small and definition of underestimation was not appropriate for underweight children, the sample of underweight children was not further analyzed.
A total of 1405 students (754 boys and 651 girls), 7.5 to 11 years of age (mean age 9.5 years) were selected for the final analysis. Among them, 327 students were obese/overweight (203 boys and 124 girls) and 1078 had a normal BMI (551 boys and 527 girls). Univariate analyses showed that male sex, birth weight ≥4000 g, Caesarean delivery, prenatal practices related to music, speed of eating <10 min, no picking at food, living together with grandparents, father and/or mother being obese, and higher family income were significantly associated with childhood obesity/overweight. In addition, a significant proportion of parents and grandparents underestimated their child’s weight status (Table 1).
TABLE 1.
Comparison of demographic characteristics, prenatal practice, lifestyle, family factors and cultural practice between obese/overweight children and children with normal body mass index (BMI)
| Factor | Obese/overweight (n=327) | Normal BMI (n=1078) | P |
|---|---|---|---|
| Sex | |||
| Male | 203 (62.1) | 551 (51.1) | 0.001 |
| Female | 124 (37.9) | 527 (48.9) | |
| Birth weight, g | |||
| <4000 | 280 (85.6) | 998 (92.6) | 0.001 |
| ≥4000 | 47 (14.4) | 90 (7.4) | |
| Mode of delivery | |||
| Caesarean | 168 (51.4) | 440 (40.8) | 0.001 |
| Vaginal | 159 (48.6) | 638 (59.2) | |
| Prenatal practice | |||
| Yes | 206 (63.0) | 572 (53.1) | 0.002 |
| No | 121 (37.0) | 506 (46.9) | |
| Speed of eating, min | |||
| <10 | 82 (25.1) | 112 (10.4) | <0.001 |
| ≥10 | 245 (74.9) | 966 (89.6) | |
| Picking at food | |||
| Yes | 181 (55.4) | 726 (67.3) | <0.001 |
| No | 146 (44.6) | 352 (32.7) | |
| Living together with grandparents | |||
| Yes | 134 (41.0) | 372 (34.5) | 0.033 |
| No | 193 (59.0) | 706 (65.5) | |
| Obesity of parents | |||
| Father and/or mother obese | 147 (45.0) | 349 (32.4) | <0.001 |
| Neither obese | 180 (55.0) | 729 (67.6) | |
| Family income (per capita income, yuan per month) | |||
| ≤3000 | 132 (40.4) | 497 (46.1) | 0.039 |
| >3000 | 195 (59.6) | 581 (53.9) | |
| Underestimation of weight by parents | |||
| Yes | 189 (57.8) | 471 (43.7) | <0.001 |
| No | 138 (42.2) | 607 (56.3) | |
| Underestimation of weight by grandparents | |||
| Yes | 227 (69.4) | 548 (50.8) | <0.001 |
| No | 100 (30.6) | 530 (49.2) | |
Data presented as n (%) unless otherwise indicated
Table 2 presents the crude and adjusted ORs for different variables for childhood overweight/obesity in boys compared with girls. The crude OR of obesity/overweight for boys compared with girls was 1.57 (95% CI 1.22 to 2.01). The increased risk of childhood overweight/obesity for boys remained after adjusting for prenatal and infant factors, daily lifestyle and family factors, but disappeared after adjusting for underperception of weight status by the parents and grandparents (OR 1.28 [95% CI 0.93 to 1.68]). Table 3 shows the ORs of parental and grandparental underestimation of boys’ weight status compared with that of girls (OR 1.33 [95% CI 1.08 to 1.64] and OR 1.42 [95% CI 1.15 to 1.75], respectively).
TABLE 2.
Association of sex (boys compared with girls) with childhood obesity/overweight
| Model | OR (95% CI) |
|---|---|
| Crude | 1.57 (1.22–2.01) |
| Adjusted for prenatal and infant factors | 1.45 (1.11–1.88) |
| Adjusted for prenatal and infant factors and family factors | 1.45 (1.12–1.89) |
| Adjusted for prenatal and infant factors, family factors and lifestyle factors | 1.38 (1.06–1.81) |
| Adjusted for prenatal and infant factors, family factors, lifestyle factors, and underperception by parents and grandparents | 1.28 (0.93–1.68) |
TABLE 3.
Comparison of the underestimation of weight status between male and female Chinese school children
| Weight status | Boys (n=754) | Girls (n=651) | OR (95% CI) |
|---|---|---|---|
| Underestimated by grandparents | 446 (59.2) | 329 (50.5) | 1.42 (1.15–1.75) |
| Underestimated by parents | 379 (50.3) | 281 (43.2) | 1.33 (1.08–1.64) |
Data presented as n (%) unless otherwise indicated
DISCUSSION
In the present cross-sectional analysis, we studied the sex disparity of obesity/overweight in school children in China. To our knowledge, the present study was the first to examine parents’ and grandparents’ perception as a possible underlying factor contributing to the sex differences in the prevalence of obesity among Chinese children.
Our study found that the prevalence of obesity/overweight was greater in boys than girls, which is consistent with previous studies performed in China (13). Additionally, our study demonstrated that higher birth weight, birth by Caesarean section, prenatal practice, fast eating, not picking at food, living together with grandparents, parental obesity and higher family income increased a child’s risk for developing childhood obesity/overweight.
We observed that a high proportion of parents and grandparents underestimated their child’s weight status. A study from Brazil reported that a caregiver’s attitude affected eating styles, food preferences and choices, which ultimately contributed to childhood obesity (19). In Chinese societies, parenting is influential in determining a child’s lifestyle during growth and development (20). Traditional Chinese society emphasizes paternal familial control and obedience (21). Misestimating a child’s weight may result in unhealthy parenting behaviours and may cause the child to become obese (22). There were some similarities between our study and the study by Lundahl et al (22), which demonstrated that many parents are unaware of their children’s overweight/obese status and parents are more likely to underestimate the weight status of their sons compared with their daughters. However, our study differs from that study in that a large proportion of parents (50.7%, based on adjusted effect size) underestimated the weight of their overweight/obese children in the present study, compared with only one of seven parents underestimating their child’s normal weight reported by Lundahl et al (22). The association between parents’ perception of their child’s weight and parenting behaviours suggests that the accurate classification of a child’s weight is important to prevent childhood obesity.
The higher prevalence of obesity/overweight in boys than in girls in our study is consistent with previous reports from China. The increased risk of childhood obesity/overweight for boys remained after adjusting for prenatal and infant factors, daily lifestyle and family factors, but disappeared after adjusting for the underperception of weight status by parents and grandparents. Furthermore, parental underestimation of a child’s weight status was also higher for boys compared with girls. The sex difference in the prevalence of childhood obesity may be partly related to these factors. Additionally, the primary reason for this sex difference may be related to social values and cultural factors (23–25). In China, most elderly individuals believe that boys should be strong, and sometimes being overweight is regarded as a sign of strength. In contrast, girls with a slender and graceful stature are favourably perceived by Chinese society. Chinese parents may be more sensitive to girls’ weight and body image, while larger boys may be viewed as having a physical advantage. Therefore, parents may adopt more behaviours focused on diet and exercise to control girls’ weight than for boys, which could lead to more obese/overweight boys than girls.
The present study was also the first to report that grandparents underestimated the weight status of boys more than girls, contributing to the sex difference in the prevalence of obesity. In China, each couple is allowed to have only one child as a measure of birth control; thus, the child is very important in the large family. Many three-generation families exist, in which grandparents are the primary adults caring for the children and they control children’s diets. The grandparents will urge children to exercise, restrict their television viewing time and reduce high-calorie and high-fat diets if they believe the children are obese or overweight (23). In contrast, they may not restrict such diets if they do not believe the children are obese or overweight. Grandparents’ tendency to underestimate a child’s weight status may result in prompting children to overeat and exercise less.
Our study had several limitations. The study sample was selected only from limited urban areas in central south China; therefore, the results may not be applicable to all Chinese school children. We are not aware of whether these perception differences exist in rural areas because social values and cultural factors differ between rural and urban areas. Furthermore, cross-sectional data were used in the analysis, and inferences regarding causal effects cannot be made. Our sample was limited to children 7.5 to 11 years of age and did not represent all school stages. However, our sample may have avoided the bias of lack of understanding of the questionnaire among younger children, and the possible effect of endocrine hormones in older children. As a result, the sample selection may have yielded results that were easier to interpret.
CONCLUSIONS
Misconceptions about a child’s weight status are prevalent among Chinese parents and grandparents, and boys’ weight status was more frequently underestimated than girls. The disparity of underestimating according to sex may partially contribute to the difference in the prevalence of obesity/overweight between boys and girls among Chinese school children. The present study highlights the need to provide accurate information regarding a child’s weight status to parents and grandparents, and to consider their perceptions as factors while planning interventions to prevent childhood obesity.
ACKNOWLEDGMENTS AND DISCLOSURES:
This project was sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry. The authors thank the children, parents and staff of the participating schools for their support. The authors have no conflicts of interest to declare.
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