Awareness and accuracy of height and weight among mothers and their preschool aged children

Abstract

Objectives:

A constant challenge in addressing the issue of obesity is the validity and reliability of self-reported measurements to calculate Body Mass Index (BMI), that assesses the prevalence of obesity in a population. The objective of this study is to analyze both awareness and accuracy of mothers who are overweight or obese, in reporting their own and their child’s height and weight measurements.

Study design:

Cross-sectional study

Methods:

In this study, mothers were asked over phone to self-report height and weight for them and their child. This was followed by objective measurement of maternal and child height and weight by study staff in a clinical setting. The descriptive and statistical analysis of the data obtained was done using SAS software.

Results:

1. The mean weight of mothers who inaccurately self-reported their weight was 9.5 kilograms greater than the mean weight of those who reported accurately (p<0.001).

2. Despite being aware of, and reporting their own measurements, 50% (N=116) of mothers reported not knowing their child’s height and 23% (N=54) of them reported not knowing their child’s weight.

Conclusion:

Strategies to tackle both maternal awareness and accuracy of child’s measurements can help with early identification of child’s obesity risk and prevention of long-term consequences.

Identifying children who are at risk for excess weight, early in their childhood, is critical to the delay and prevention of obesity. The family environment, and specifically a mother’s responsiveness towards child’s weight plays a crucial role in targeting intervention strategies. This becomes even more important in circumstances where the mother herself is overweight or obese.

Evaluating prevalence of obesity in a population is often relied on self-reported (for adults) or parental reported (for children) measures in order to avoid burden and cost of collecting measured heights and weights. Studies so far have assessed perceptual accuracy of reported measures among different population groups based on age, BMI, gender, geographical location and cultural factors. In this study we focus on families where mothers are either overweight or obese and aim to analyze height and weight reported by mothers, both for themselves and their pre-school aged children. We hope that our study in St. Louis region can provide an empiric emphasis for regions across US with high rates of childhood obesity.

This cross-sectional study design used baseline self-reported and measured heights and weights of mothers and children who were enrolled in ‘Healthy Eating and Active Living Taught at Home’ (HEALTH), a parent focused weight-loss intervention study.¹ The HEALTH study was conducted in partnership with Parents As Teachers (PAT), a nonprofit home visiting organization that supports optimal early development, learning, and health of young children, currently serving more than 195,000 children across the United States.² Mothers (N=230) who were registered in PAT programs across eight St. Louis, Missouri regions participated in this study. Inclusion criteria for the study were female participants between 18 to 45 years of age, with BMI of 25–45 kg/m², having at least one preschool child at risk for overweight living in the home, plans to continue in PAT program for two years, and able to give informed consent. The exclusion criteria included pregnant women or those planning to become pregnant in the next 24 months, unable to speak English, enrolled in a weight loss program, undergoing treatment for diabetes or eating disorders, or inability to engage in a walking program.¹

During the enrollment phase, mothers were asked over phone to report their height and weight, and their child’s height and weight. This was followed by an in-person assessment visit, which typically took place within one month of the telephonic survey, when height (in feet and inches) and weight (in pounds) were measured by trained staff in accordance with procedures used by National Health and Nutrition Examination Survey (NHANES).³ Seca 213 Portable Stadiometer and HealthOMeter 349KLX Digital Medical Weight scales were used to measure height and weight respectively. The 2000 Centers for Disease Control and Prevention growth charts⁴ were used to calculate BMI percentiles for children. BMI for mothers was calculated with height and weight measures using the formula BMI = weight (in kg) / height (in m)². Participation in the study was limited by lack of any randomization, and all families that met the inclusion criteria were eligible for enrollment including those who reported not knowing height and weight measurements.

In this study, awareness was defined based on their knowledge of the measurements. Those who did not know their measurements were classified as ‘unaware’ and those who knew their measurements were categorized based on the accuracy into ‘accurate’ and ‘inaccurate’. Using SAS software, a descriptive analysis was performed to analyze frequencies of reported measurements of height and weight both for mothers and children. Mean and standard deviation for reported and measured heights, weights, BMIs (mothers) and BMI percentiles (children) were also calculated. Pearson’s correlation was used to assess associations between self-reported and measured values.

Mother’s weights were categorized based on the accuracy of reporting status, while children’s weights were categorized based on both awareness and accuracy of reporting status. An acceptable difference of +/− 2 kilograms was used to consider mothers as ‘accurate’ in their weight reporting. Based on this criterion, mother’s weights were grouped into two categories – accurate and inaccurate. Studies on children show that a small difference of 0.5 kilograms can change their BMI percentile from one category into another, leading to a misclassification of their weight status.⁶ Hence a criterion of +/− 0.5 kg was used to classify child’s weight, yielding three groups of reporting statuses - accurate, inaccurate and unaware. After categorization, independent t-test (for mothers) and one-way ANOVA (for children) was used to look for statistically significant differences (p<0.05) in the measured mean weights and BMI.

The mean maternal age of the study population was 32 years (SD 6.0) and ages of children ranged from 2 – 4 years with mean age of 3.4 years (SD 0.81). Descriptive analysis on reported measurements showed that 2% of mothers (N=4) did not report their own weight, and less than 1% (N=2) did not report their own height. When asked to report their child’s measurements, 23% (N=54) did not report their child’s weight and 50% (N=116) did not report their child’s height. For their own measurements, the mothers’ reported and measured weights were highly correlated (r=0.95, p<0.001) as were their reported and measured heights (r=0.94, p<0.001), and BMI (r=0.93, p <0.001). Among children, there was strong correlation between reported and measured weights (r=0.86, p<0.001) and heights (r=0.69, p<0.001), while for BMI percentiles a significant but weak correlation was found (r=0.24, p=.009) (Figure 1).

Figure 1:

Graphical representation of differences and correlation between self-reported and measured BMI (for mothers) and BMI percentiles (for children)

*those with missing self-report were not included in the figure

Mothers who reported their weight inaccurately had a mean weight that was 9.5 kg more than the mean weight of those who accurately reported their weight (99.13 vs. 89.61 kgs, p<0.001). Correspondingly, mean BMI of mothers in the inaccurate group was 3.5 kg/m² higher than mean BMI of mothers in the accurate group (36.66 vs. 33.23, p<0.001). While reporting their child’s measurements, 45% of mothers accurately reported their child’s weight, 32% reported it inaccurately, and 23% were unaware of their child’s weight. Among children’s categories (accurate, inaccurate and unaware), the mean weights and BMI percentiles were not significantly different.

This study aimed to analyze both awareness and accuracy of mothers who are overweight or obese, in reporting their own and their child’s height and weight measurements. The two main findings were that 1) mothers who reported their own weight inaccurately had mean weight and BMI that was significantly higher than those who reported their weight accurately, and 2) significant proportion of mothers reported not knowing their child’s height and weight, despite being aware of and reporting their own measurements.

While most studies so far focused on parental perception of their child’s weight status or category, our study was unique in comparing the individual’s precise reported measurement to that assessed by the researcher. We identified that despite very good correlation between reported and measured heights and weights for children, their BMI percentiles were significantly but weakly correlated. Another finding was that even though mothers self-reported their own weight, 23% of mothers reported not knowing their child’s weight and 50% of them did not know their child’s height, meaning they were unaware of their child’s obesity risk. An important limitation though is the empirical approach of using BMI rates than fat mass index, which is a much better predictor of obesity.⁶

While studies to date mostly looked at accuracy of parental perception on reporting their child’s height, weight or BMI, our study found that significant proportion of mothers were unaware of their child’s measurements in the first place. This implies that developing strategies to give parents a clear understanding by keeping them informed on the accurate estimate of their child’s weight is a prerequisite step in preventing progression to overweight, and for early treatment of obesity. To tackle this, it is also important to consider reasons why mothers are unaware of their child’s measurements. A study that looked at low-income mothers’ concern about their preschoolers being overweight found that child’s measurements on growth charts didn’t provide any understanding to mother’s about their child’s weight status. Instead, the only factors that mothers considered to define their child’s overweight status were, child being teased about his/her weight and any limitation in the child’s physical activity.⁷ Another study identified that mothers are more likely to recognize their child as being overweight when their child is older (>= 6 years), but not during the early preschooler stage.⁸ Other reasons could be lack of regular visits to the pediatrician due to financial constraints, lack of understanding about importance of periodic monitoring of child’s measurements, mother’s own motivation and lifestyle habits, or failure to receive tangible help from health professionals.⁹ Lastly, a subtle but important factor to consider is that maternal-blaming exaggerated through professional literature and media messages could lead to maternal denial of child’s overweight status.¹⁰ Based on these assumptions, primary care providers, social media and governmental policies can play crucial roles in overcoming obstacles, increasing accessibility and implementing non-stigmatizing approaches towards maternal awareness on childhood obesity. Thus, prevention of obesity requires a multi-level approach and findings from our study call for measures to identify strategies that tackle both unawareness and misperception of height and weight for both mothers and their children.

Highlights: Awareness and accuracy of height and weight among mothers and their preschool aged children.

• Early identification of obesity risk among children is a crucial preventive measure

• Mothers with higher weight self-report their measurements inaccurately

• Mothers unaware of child’s measurements, despite knowing their own height and weight

• Need for strategies to tackle both awareness and accuracy of measurements