Growth and development are hallmarks of pediatrics. Nutritional and growth statuses are assessed based on weight (W) and height (H). In the development of indicators, sex and age are accounted for assessing H and W, as appropriate gains in H and W based on sex and age, and their relationship, expressed as body mass index (BMI), are essential for healthy growth. Most references, including those in Korea, provide growth charts for each sex [1]. W for age and W for H is recommended for very young children. However, W for age ignores H and W for H ignores age. This paper focuses on early childhood health checkups in subjects aged 24 months or older in Korea.

Child malnutrition is a major public health issue and the “double burden of malnutrition” is an important global health issue [2]. Attention should be paid to both overweight and underweight conditions during early childhood and the patterns of malnutrition, especially faltering growth conditions, such as stunting or wasting, should be addressed in early childhood [2]. To maintain a healthy W (Stay Healthy), it is necessary to understand the two extremes of malnutrition and to use appropriate growth charts in routine childhood health checkups.

Fig. 1 shows the BMI references and example patterns of adiposity rebound. The term underweight can be used for a BMI less than the 5th percentile, as a counter to overweight. Overnutritional status was defined as overweight, including obesity. Overweight is defined as a BMI equal to or greater than the 85th percentile (BMI z score ≥1.04) and is further classified into obesity class 1, 2, or 3 (Fig. 1). The importance of the 85th percentile of BMI should be addressed in detail.

Adiposity is a useful metric for monitoring fat development and nutritional status in children. During growth, adiposity varies and is positively correlated with both H and W. However, the correlation is not equal, and is greater with W than with H. Despite its limitations, BMI has been selected as a proxy of adiposity [3]. It is now used globally, and reference percentiles for Korean children are also available [1].

Adiposity rebound (AR) refers to an increase in BMI after a nadir and a change in the BMI percentile in early childhood. If a child’s BMI percentile remains stable with age, it suggests that W gains have been healthy, but if it drifts upward, it suggests too much W gain compared with H gain. Serial plotting of a child’s BMI for age can provide early signals that a child is gaining W too rapidly (Fig. 1). This is an early warning to enable parents and guardians to detect unhealthy changes during the growth period.

The age at AR has been identified as an indicator of adult fatness [4] and helps to identify the critical periods of adiposity development and risk factors for future obesity [5]. Early AR, based on the definition of age at AR <5.0–5.1 years, may be an effective marker of obesity and the prevalence of early AR is increasing [5]. Sex differences have been reported, with girls experiencing AR earlier than boys [5]. Recently, the occurrence of AR has been reported at the age of 3 years and it has been suggested that modifiable daily routines, such as breakfast and napping at the age of 1.5 years, may help delay AR [6].

Counselling to help understand the significance of AR and the meaning of changes in BMI percentiles is an essential part of clinical practice. If a health risk tendency is observed in the growth pattern, either overweight or underweight, a comprehensive lifestyle assessment and interventional counselling, including living and parenting (child-rearing) environments, are necessary. Therefore, there is an urgent need for a cooperative and supportive health care system.

A BMI ≥the 85th percentile should be addressed as a starting point of excess adiposity with rapidly increasing adiposity. The relationship between BMI and fat mass is markedly nonlinear, and substantial differences in fat mass are seen only at BMI levels ≥the 85th percentile [7]. The 85th percentile is not provided for H, W, or W for H. The 85th percentile cutoff is based only on the BMI growth curve.

In 2007, the prevalence of metabolic syndrome in Korean adolescents with overweight was reported 22.3% significantly higher compare to normal W (1.6%), and early identification with target interventions was highly recommended [8].

To enhance early identification without confusion and encourage lifestyle intervention at school, among three overweight screening criteria, BMI 85th percentile has been selected as the cut off and weight 120% of ideal for height is no longer used in Student health checkups [9].

In the concept of “clinical obesity” as a disease, “excess adiposity” based on body composition measures is an essential component of the assessment of obesity beyond BMI [10].

In conclusion, healthy growth, nutrition monitoring, and the promotion of adequate adiposity are essential in pediatric practice. Thoughtful tracking of the H, W, and BMI percentiles by addressing the age of AR in early childhood might be an early and effective strategy for preventing obesity and decreasing the double burden of the disease in later life.