Determinants of weight gain in children from 7 to 10 years

Abstract

Background and Aim

To determine the influence of the family risk factors (parental weight, socioeconomic status and cultural level) on the distribution of overweight or obesity in prepubertal children and the dynamics of their weight gain.

Methods and Results

Three hundred forty-one children (183 boys) attending the second grade of primary school (age 7.4 ± 0.5 years) were enrolled in a longitudinal study in Southern Italy. Overweight and obesity status were defined by a body mass index (BMI) above the percentile having respectively the value of 25 and 30 kg/m² at 18 years, according to national reference data; overweight extent was expressed as BMI standard deviation score (BMI-SDS). Information about BMI and socioeconomic conditions (occupation and educational level) of parents were collected. Distribution of overweight and obese schoolchildren and variations of BMI-SDS were evaluated over a 3-year period; relationships with family risk factors were also sought.

The distribution of overweight/obese children at baseline was high (40%). Tracking rates of overweight and obesity were 73% and 80%, respectively. The higher the BMI-SDS at 7 years, the higher the BMI-SDS at 10 years (r 0.86, P = 0.0001). The highest BMI value and the highest distribution of overweight/obese children were observed in subjects with the highest amount of family risk factors. Children exhibiting accelerated weight gain (delta BMI > 1/year) showed higher male/female ratio, higher baseline BMI values, higher maternal BMI values, lower maternal educational level and a dramatic increase in the percentage of overweight/obese children than children with normal weight gain.

Conclusions

Children who are overweight/obese at 7 years tend to maintain this condition during prepubertal age. Paediatricians should be alerted when dealing with a child showing a BMI increase above than 1 U/year during primary school. Targeted intervention should be directed at young children with overweight parents and low socio-cultural level.

Introduction

The prevalence of overweight among preschool and school-aged children is increased in all developed countries at an alarming rate. This “epidemic” increase strongly indicates the crucial role of environmental factors, which contribute to influence the behavioural control of food intake and lifestyle in concert with genetic factors. Risk factors mainly include parental obesity, socioeconomic status (SES), birth weight, diet and physical activity patterns [1]. The importance of genetic factors is strongly underlined by family resemblances in weight status. On the contrary, the relationship between social factors and childhood obesity showed somewhat equivocal results. It has been reported that in developed countries children from lower socioeconomic classes are more likely to be overweight, while other studies showed no association at all [2]. No clear relationship is reported between SES in early life and childhood fatness. However, a strong consistent relationship was observed between low SES in early life and increased fatness in adulthood [3].

The literature suggests that a series of biological factors, such as the timing of adiposity rebound (AR), i.e., when BMI increases after its nadir in childhood, and parental obesity are suspected to influence the early development of obesity and to condition its persistence in adulthood [4], [5]. Several studies focused on tracking of the BMI patterns from childhood to adulthood, while little research has been devoted to the dynamics of body mass increase in shorter periods during childhood. Understanding the factors which might influence the early occurrence of overweight and tracking offers further opportunities for obesity prevention.

Therefore, the aim of the present study was to determine the influence of family risk factors for overweight, represented by parental weight, socioeconomic status and educational level on the distribution of overweight/obesity in children at the beginning of primary school. The influence of these factors on the dynamics of weight gain over a 3-year period was also sought.