Background
Worldwide reports reveal that obesity has tripled in the last 40 years [
1]. In 2016, 41 million children younger than 5 years and 340 million children and adolescents aged between five to nineteen years, were overweight or obese [
1]. Overweight and obesity represent already a health issue in childhood. Obesity in early childhood is associated with an increased risk of obesity in adulthood [
1]. Therefore, prevention is already needed at a young age.
Obesity is a heterogeneous disease and is characterized by abnormal or excessive fat accumulation. Body fat percentage (BFP) is strongly associated with the risk of several chronic diseases and a massive increased fat mass leads to obesity defined as abnormal or excessive fat accumulation [
2]. The body composition (BC) differs essentially between children and adults [
3]. In addition, gender, age, health conditions, and ethnical background have an impact on body composition [
4,
5]. However, it’s accurate measurement is of utmost importance. The body mass index (BMI) does not differentiate between fat mass (FM) and fat free mass (FFM) [
6]. Different body composition measurement techniques exist and range from underwater weighing (densitometry), dual energy x-ray absorptiometry (DEXA), magnetic resonance imaging (MRI) to bioelectrical impedance analysis (BIA). Most of these methods either expose the patient to radiation, are time consuming, inconvenient and expensive. Therefore, the non-invasive bioelectrical impedance analysis measurement appears to be a useful and feasible tool, especially for young pediatric populations. This device is fast in the measurement, inexpensive compared to other techniques, gives reliable measurements of body composition with minimal intra and inter-observer variability and is reproducible with < 1% error on repeated measurements [
7].
There is a lack of knowledge of body composition in pediatric patients with obesity. Moreover, no data are available on the comparison of two clinically relevant body composition methods for children. The aim of this study was to investigate the differences between two bioelectrical impedance analysis techniques performed in children and adolescents with obesity. Furthermore, we analyzed if gender has an impact on the body composition in children and adolescents.
Discussion
In the present study, body composition of a young population with obesity was evaluated by using two methods, namely TANITA and BIA-BIACORPUS devices. We observed low agreement between the two body composition methods and Bland-Altman postulates the non acceptable level of agreement between the two methods.
Significant differences between both body composition methods were detected. The Pearson correlation coefficient is commonly used for measuring the association between two methods. Results might be misleading and therefore Bland Altman plot has been used to determine the limits of agreement. The Bland Altman plots demonstrated a low agreement between the body composition methods. An upper and lower margin of more than ±5 kg can be defined as clinically relevant. The outcomes demonstrated that fat mass, fat free mass and total body water were exceeding this threshold. Moreover, the upper and lower margin of body fat percentage was more than ±5%, and basal metabolic rate was more than ±250 kcal. TANITA overestimated body fat percentage, fat mass and basal metabolic rate. The higher the total body fat percentage and fat mass was, the higher the deviation between the measurements was observed. The outcomes indicate that body composition should always be performed by the same body composition device to obtain comparable results.
We have observed gender differences in regard to the body composition. Male individuals had with TANITA and BIA an increased muscle mass, which results in an increased energy burning. This in coherence with our findings of an accelerated and higher basal metabolic rate and was displayed in a decreased body fat percentage and increased fat free mass. Male individuals usually have increased total body water, as they have an increased muscle mass [
17]. Those outcomes are consistent with our results measured with TANITA and BIA. In girls, body fat percentage and fat mass were increased in comparison to boys, which is in line with the literature. One main factor is puberty induced fat deposition in hips, thighs and growing breast tissue in the girls [
18]. Body fat percentage is a main factor to determine obesity. The outcomes established that body fat percentage for obesity in girls was over their age recommended cut-off levels of ≥35% body fat percentage and in boys over the cut-off ≥25% body fat percentage [
19]. The fat distribution has an impact on health, which can be determined with waist circumference. An increased health risk is defined by a waist circumference in women > 88 cm and for men > 102 cm [
20]. For children and adolescents-specific cut-off values are not available. However, our results indicated that girls as well as boys were above the announced cut-off values for waist circumference and have therefore an increased health risk. Intra-abdominal, also called visceral body fat, is located in the core abdominal area and is correlated with an increased health risk [
1]. No significant gender differences in abdominal fat have been noticed. However, patients had an increased android fat distribution, which is related with an increased cardiovascular and metabolic risk as well as insulin resistance [
21].
Recent data explored that in Austrian children and adolescents aged 4 to 19 years, 18% of boys and 12% of girls were overweight and 5% of boys and 3% of girls were obese [
22]. Hence, overweight and obesity is already an issue in Austria and prevention is needed. An increased body mass in particular increased body fat percentage is strongly associated with the risk of several chronic diseases [
1]. During growth the body composition changes [
3].
The percent body fat increases about 11% from infancy to 6 months of age. Then, body fat percentage decreases (males 11%, girls 7%) from 6 months up to the age of 10 years [
4]. Especially in patients with obesity, the body composition has to be monitored.
There is no gold standard in the body composition measurement in a pediatric study population with obesity. However, the TANITA scale and BIA-BIACORPUS are non-invasive, fast and easy in the measurement, and highly accepted by children and adolescents. Bioelectrical impedance analysis does not require exposure to radioactivity or submersion in water, and therefore it is a practical measure of body composition, especially in the clinical routine with children. Bioelectrical impedance analysis devices, like TANITA, are frequently used in a young population. Several studies conducted in children and adolescents have shown a good level of accuracy in comparison to reference body composition methods [
23‐
26].
However, other studies revealed a low level of accuracy [
27‐
30], which might be caused by differences in used BIA devices, reference methods and study populations in regard to ethnicity and age.
Detailed information about the body composition in children and adolescents with obesity evaluated with two different body composition methods have not been evaluated so far in Austria. This study explores the body composition measurement differences of two methods used at a clinical setting in such a pediatric study population with obesity. Body composition should always be measured with the same device to obtain comparable results.
A limitation of this study is the lack of other analysis techniques such as DEXA, MRI or air displacement plethysmography [
31]. However, those methods cannot be used within the clinical routine in pediatric obese patients. DEXA, which is often announced to be a gold standard in body composition measurement, is in pediatric patients not feasible as this method involves radiation exposure and the procedure takes up to 20 min and patients should not move within the measurement. Moreover, trained radiology personnel is required and the measurement is expensive. There is no gold standard in body composition measurement in pediatric patients with obesity. However, at clinical routine due to its feasibility, safety, and efficiency, bioimpedance analysis is the most often used body composition method, especially performed in pediatric patients.
Conclusions
In conclusion, data suggest a low agreement between the TANITA scale and the BIA-BIACORPUS. TANITA overestimated body fat percentage, fat mass, and basal metabolic rate in comparison to BIA. Body composition measurement should always be performed by the same devices to obtain comparable results. Nonetheless, at clinical routine due to its feasibility, safety and efficiency, bioimpedance analysis seems appropriate for obese pediatric patients.
Acknowledgements
We would like to thank the Children’s Knees team Brian Horsak, Caterine Schwab, Richard Crevenna, Keilani Mohammad, Barbara Wondrasch, Arnold Baca, Stefan Nehrer and Andreas Kranzl.