Introduction

Most of the Asian countries are fast catching up with the West on obesity [1]. Thailand showed one of the highest rates of obesity in Asia [1]. The prevalence of obesity (≥BMI 25 kg/m2) in adults doubled from 18.2% in 1991 [2] to 34% in 2008–2009 in Thailand [3]. A similar increase has been observed in children, with childhood obesity becoming a big public health concern in Thailand. According to the National Health Examination Survey (2008–2009), the prevalence of overweight or obesity was 14.9% in children aged 10–14 years [4]. A recent study of children aged 6–12 years in Bangkok showed a higher prevalence of obesity (19.3%) [5]. Thus, research attention has increasingly focused on efforts to reduce childhood obesity.

Parental involvement and support has been found to be a promising strategy for the prevention and treatment of childhood obesity [6, 7]. Parents’ ability to take action with regard to their child’s weight problems is dependent on the awareness of their child’s weight [8, 9], which is used in explaining the relationship between weight status and weight control behavior [10]. Parents who underestimated their child’s weight were less likely to report concerns [11, 12], which may lead to a lack of motivation to help children to reduce weight and to foster healthy behaviors. According to a recent systematic review [13], the magnitude of misperception, particularly underestimation of their child’s weight differed in varies studies [11, 13,14,15,16,17,18,19], probably due to various methodological limitations [18] and different cultural backgrounds. To our knowledge, there has been a lack of studies on parental perceptions of child’s weight and its relation to perception of child’s health behaviors in Southeast Asian countries facing a rising burden of obesity. Therefore, the present study aimed to assess parental perceptions of their child’s weight and health behaviors and to identify socio-demographic characteristics affecting discordance between parental perception and actual child’s weight status within family norms. By doing so, this study may provide evidence for parental misperceptions in future interventions aiming at tackling childhood obesity.

Methods

Study design and participants

In a cross-sectional study, all students in 4th–6th Grade classes (Mean age = 10.6, SD = 0.93) were randomly selected by cluster sampling in two primary schools in Nakhon Pathom province, a suburban area in Thailand. The approval from the director of each school was obtained after the study design and purpose had been explained. Parents were invited by letter to respond to a self-administered questionnaire. The students were requested to complete a self-administered questionnaire under the supervision of trained researchers, who also conducted anthropometric measurements with the children. The response rates of children and their parents were 100 and 88%, respectively. Of 609 parent–child dyads, only 525 dyads were included in the analysis due to missing values on parental information.

Materials and methods

For anthropometric data, students were weighed and measured by trained researchers using standardized protocols [20]. Children were asked to wear light indoor clothing and without shoes during the measurements. Child’s weight was measured to the nearest 100 g, using a digital weight scale, and height was measured at standing without shoes to the nearest 0.1 cm using a wall-mounted wooden stadiometer.

As the prevalence of overweight or obesity was greater when using the WHO criteria (37.2%) compared to Thai Growth Reference (TGR, 23.1%) and the International Obesity Task Force (IOTF, 30.9%), the World Health Organization (WHO) reference may be recommended to identify school children at risk of overweight or obesity at the population level in our previous study (data not shown). This supports the WHO reference as a better predictor to estimate school-aged children at risk. Yet, as a recent review revealed that the IOTF definition of obesity is highly conservative [21], the IOTF criterion seems to be more accurate to define obesity and overweight in confirmation of a disease in clinical context. The use of IOTF showed the better agreement with the TGR in estimation of the prevalence of combined overweight and obesity (data not shown). In addition, many studies reported that the IOTF criterion seems to be a more suitable one to guarantee the multi-ethnic and cultural application [22, 23]. Therefore, we used age- and gender-specific BMI values using the extended IOTF BMI cutoffs reformulated by Cole et al. in 2012 [24], which used underlying LMS (Least mean Square) curves. The cut-off for weight status for Asian children was <16 for severely underweight, 16–16.9 for underweight, 17–24.9 for normal weight, 25–29.9 for overweight, and ≥30 for obesity.

The questionnaire for a parent or caregiver included items on parental concern (2 items), perception of their child’s weight (1 item) and health behaviors (3 items) that were adapted from previous studies [25, 26]. Parental concern questions included, “I am worried my child is overweight right now” and “I am worried my child will become overweight”, with response options ranging from 1 = “disagree a lot” to 5 = “agree a lot”. The responses were dichotomized to agree or disagree (including the neutral answer) for parental concern. For parental perception of their child’s weight, parents were asked to rate their child in comparison with other (his/her age) children’s weight (much thinner, thinner, similar, overweight, or much more overweight). Health behaviors regarding their child’s diet, activity level and amount of food had the response options ranging from ‘much less healthy’ to ‘much more healthy’ healthiness of diet, from ‘eats much less’ to ‘eats much more’ for amount of food eaten and from ‘much less active’ to ‘much more active’ for activity level. The responses were grouped to ‘less’, ‘about the same’ or ‘more’ for parental perception.

Data analysis

The child’s weight status was compared with parental perception of their child’s weight on 5-point scales from ‘much thinner’ to ‘much more overweight’. Cohen’s Kappa test was used to assess the inter-rater agreement between the percentages of parent’s perception of their child’s weight in each of child weight categories. We further assessed the concordance using the Kappa value and it can be interpreted by the strength of agreement: 0 to 0.20 (poor); 0.21 to 0.40 (fair); 0.41 to 0.60 (moderate); 0.61 to 0.80 (good); 0.81 to 1.00 (very good).

For further analyses, parental perceptions were classified as concordant, underestimation and overestimation compared to child’s actual weight. Since the prevalence of the overestimation was much lower than the underestimation of the weight status, and underestimation particularly among overweight/obese children may result in low motivation to reduce excess weight [27], comparison between parents who accurately perceived and those who underestimated their child’s weight were estimated using student t test for continuous variables or Chi-square tests for categorical variables. Separate analyses were conducted for normal weight and overweight/obese children. Statistical analyses were conducted with SAS for Windows (version 9.3).

Ethical considerations

All procedures were conducted after ethics approval from the Human Research Ethics Committee of Mahidol University, Thailand (Approval No.: 2015/033.2701). Informed assents from children and informed consents from their parents were obtained after explanation of the study objectives and assurance of the confidentiality of their identity.

Results

The prevalence of thinness, overweight and obesity among children when estimated by the IOTF cut-off points was 5.7, 19.1, and 10.7%, respectively. The percentage of the total agreement between parental weight estimate and measured weight status of the child was 59.2% (κ = 0.49). Parental perceptions of their child’s weight according to their children’s weight status are presented in Fig. 1. About 42% of parents misperceived their child’s weight, while 6.9% of parents overestimated and 33.9% underestimated their child’s weight status. Weight underestimation was greater in parents of overweight or obese children (42.3%).

Fig. 1
figure 1

Distribution of accuracy of parental weight perception according to measured child weight status. Child weight status was categorized using the new IOTF cutoff points

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Table 1 shows parental responses regarding concern about their child’s weight and perceptions of their child’s health behaviors compared to their peers. Among parents underestimating their child’s overweight or obese status only 35% responded that they were concerned that their child was currently overweight and 34% of becoming overweight in future. In the total sample, parents who were underestimating their child’s weight status were more likely to report that their child’s diet was less healthy (57.7%) and they ate less (66.3%) and were also more active (50%) compared to their peers. When stratifying with normal and overweight children, compared to parents who correctly estimated the measured normal weight status of their child, parents who underestimated the measured normal weight of their child were more likely to report their child’s diet was less healthy (71.4%), ate less (67.1%) and were also less active (42.6%). Moreover, compared to parents who correctly estimated the measured overweight or obesity status of their child, parents who underestimated the measured overweight or obesity status were more likely to report their child’s diet was more healthy (52.3%), and ate less or similar (57%) and were more active (59.3%).

Table 1 Distribution of concordant versus underestimation of parental weight perception by parental concern and perception of child’s health behaviors according to child’s weight status
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The proportion of underestimation was significantly higher in boys (44.8%) than in girls (30.9%) and in employed mothers (38.1%) than in unemployed mothers (13.3%) (Table 2). Among children with measured normal weight, factors associated with parental underestimation were boys and children with lower BMI, higher household income, and mother’s working status, while in children with higher measured BMI, parents with only one child showed a higher proportion of underestimation than those with more than one child.

Table 2 Distribution of child and familial characteristics by accuracy of parental perception of children’s weight status
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Discussion

The percentage of the total agreement between parental perception of their child’s weight and child’s measured weight status was only 59.2%. Among the parents who misperceived their child’s weight, 82% underestimated. The underestimation may lead to a lessor concern about their child’s weight and greater optimism about their child’s health behaviors. Furthermore, the child’s gender, the existence of siblings and maternal employment status may distort the parental perception of the child weight status. These findings may call for an urgent need of family-based childhood obesity interventions in increasing more accurate estimation of child’s weight.

To our knowledge, this is one of the first studies on the accuracy of parental perception of their child’s weight in Southeast Asian countries, which makes it difficult to compare our study findings. Our results showed a high proportion of parental misperception of child’s weight. Moreover, the parental misperception was greater in children overweight or obese. In agreement with previous studies [11, 12], our study showed approximately 70% of parents of overweight or obese children reported that they were concerned about their child being overweight now and in future. Furthermore, among those parents underestimating their child’s overweight status, the proportion reporting concern was very low (only 35%). The lower concern seemed to be related to the mismatch between parental perceptions and their child’s actual weight. In a society where parental misperception of their child’s weight is common [13, 14], overweight may be normalized increasing the risk of obesity [28]. This finding is supported by a recent study where showing a generational shift in social norms related to body weight, in which the threshold BMI z-score of children for being parentally perceived as overweight increased significantly from 0.96 in 1988–1994 survey to 1.35 in 2005–2010 survey. This resulted in lower probability of overweight or obese children being correctly perceived by parents [14]. As regular weight screening may help parents to identify their child’s weight status accurately [29], schools and health care providers should provide an opportunity to screen children’s BMI status on a regular basis [8, 17, 29], and give feedback on the weight status and the health consequences of obesity to the parents as well as the children [8, 17, 18, 29].

The parental weight misperception could be related to impaired healthy development of their children [15]. Our study showed parental optimal perception on health behaviors of overweight children. For example, parents of overweight or obese children were likely to report their child’s diet was more healthy, ate less or similar and were more active. This parental misperception of child’s health behaviors can be explained partly by a tendency to underestimate one’s personal risk [30, 31]. For example, if parents had an incorrect norm [32], they were more likely to lower perceived risk [31]. On the other hand, they may cope by denying that their child’s overweight or obese weight status [30], partly because they may perceive that little can be done to solve it [16]. Meanwhile, parents who perceived their child’s overweight correctly were more likely to view their child’s health behavior patterns, such as diet and physical activity and to consider childhood obesity as a health threat [16]. These parents may more likely monitor and regulate child’s health behaviors and to encourage participating in programs addressing childhood obesity [7, 8, 16]. In addition, parents who are more likely to see health behavior of the family as well as their child [16], which may benefit the entire family as well as the children at risk [11]. Another study found that parents who expressed concern about their child’s weight were more likely to attempt to limit their child’s screen time [8] and to improve the family’s diet [8, 11].

Greater underestimation by parents was observed in boys, consistent with other studies [17, 33], despite of no significant gender difference in overweight or obese children. This finding may be attributed to the parent’s view on being fat as a positive feature representing affluence in Asian societies [34], particularly towards boys compared to girls that are placing more value on thinness [8]. In addition, different from previous studies [13] showing parents were likely to misperceive their child’s weight in younger age, our study did not show a difference in ages due to the limited target age group (Grades 4–6). However, it may suggest that public health actions to tackle obesity should start at an early age. Besides gender and age, other familial characteristics, such as maternal employment, household income, and number of children in the household were associated with BMI misclassification in our study. Regarding familial characteristics, mothers who were working or had a higher household income tended to underestimate the measured normal weight of their children in our study, although a study of Chinese mothers showed that working mothers underestimated their overweight children’s weight [34]. Meanwhile, our study showed that parents of overweight or obese children misperceived and underestimated their child’s weight when they have only one child in their household. The existence of siblings in a household may be related to the socialization of body prescribing standards and expectations related to body perceptions [35, 36] within the family system [37] by providing significant social comparison standards for body image attitudes [38] and satisfaction [39] in adulthood. This finding highlights the need of interventions, which should be directed towards the whole family to improve parental weight perception [15] at an early age of their children in order to prevent childhood obesity.

This study has several limitations. Firstly, because the study population is limited to children studying in two schools, the results may not be generalizable to the total population. In addition, of 605 parents of children only 88% of parents (60% mothers and 40% fathers) completed information on the perception on their child’s weight. Despite of no significant differences in children’s measured BMI, there may be differences in the parent’s view in the child’s weight between parents who completed the survey and those who did not, and between fathers and mothers. Next, while the weight and height were measured in children, those of the parents were assessed by self-report. However, as a high correlation between self-reported body size and BMI was observed [40], it may indicate good internal validity. Finally, this study is cross-sectional in nature, and thus no causal relationships can be drawn from these findings. Despite these limitations, this study provides useful information for future obesity interventions in South East Asia. These findings may lead to a need of development of effective strategies that increase more accurate estimation of child’s weight in the prevention and treatment of child obesity.

Conclusion

The study found an underestimation of the child’s weight status by their parents and an incorrect estimation of their child’s health behavior. Family-based weight control interventions will need to incorporate parental misperceptions of the body weight and health behaviors of their children.