Obesity and overweight has become worldwide epidemic not only in adults but also in children. Given that area differences in nutritional status could not be excluded, we surveyed the nutritional status of school children aged 9–15
yrs in Chengdu, which is one of the latest cities in Southwest China. Approximately 17.8% of school children were in excess body weight, of which 14.5% were overweight and 3.3% were obesity. The combined prevalence was twice higher than that reported in the retrospective evaluation of nutritional status in children from the 2002 China National Nutrition and Health Survey (CNNHS), which applied the same reference of WHO (2007)
]. Whereas it was still lower than the percentage of 25.7% among 10–15
yrs children in Beijing also with the same reference
]. The prevalence of obesity in this study was a little lower than that reported among children aged 10–15
yrs in Xi`an, which was also a relatively backward city in West China
]. Further compared to Asia Indian, Chengdu had a much lower prevalence of obesity
]. Compared with children aged 6–12
yrs in Chengdu 3
years before, it had nearly increased 5%
]. Trend in overweight and obesity prevalence in inland big cities of China was critically in sharp increment. Our study showed that boys were much more prevalent of overweight and obesity than girls, and the same tendency were found in other studies
]. It might contribute to the different physical growth and eating behaviors between boys and girls. Girls always eat much less than boys to keep slender. And the particular pattern of pubertal development that children were more liable to rapid accumulation of body fat and bone growth at the starting of puberty, might help to explain the gradually decrement of the combined prevalence of overweight and obesity when age increased.
While overweight and obesity of children had definitely become a great public health concern, malnutrition still existed and had significant impact on the physical health of the population, especially in developing countries
]. In present study, 6.3% of school children were thinness. There was a distinct decline from the 12-13% thinness rate of children aged 10–18
yrs from eight provinces of China in 1991–1993
], but a little decline from the national survey of 7.4% in 2004 using the same reference
]. Furthermore, it was close to that of Portugal
] and Seychelles
], but lower than that reported in West Bengal of India
]. Therefore, it implied that the malnutrition status was decreasing slowly in recent years in Chengdu. While we are arguing to focus on the overweight and obesity epidemic, we should still pay attention to the lasting problem of malnutrition in children in backward cities.
This study suggested that children born to preterm LGA were nearly at three times higher estimated risk to become overweight and obesity. Till now, there were few reports upon the relationship of preterm LGA with later overweight and obesity, whereas it was usually presented separately. Hediger et al. proposed that LGA infants grew much longer and heavier
], and these children were suggested being prone to accumulate excess fat and become overweight or obesity
]. In spite of LGA, preterm infants were also shown a higher risk of developing overweight and obesity in later life
]. Unexpectedly, preterm infants with higher birth weight but not lower birth weight were found associated with overweight and obesity among the children. It was relatively similar to our findings. Additionally, children born to full term SGA were also found liable to develop overweight or obesity in our work. This was consistent with some previous studies, which suggested that SGA children appeared to dramatically transit toward central adiposity, mainly as a result of the rapid weight gain in later life
]. However, we failed to demonstrate the relationship between preterm SGA birth and later overweight or obesity, which was proposed by other studies
]. This might arise from the differences in study design, e.g. sample size, characteristics of objects and methodology, and further longitudinal cohort study was warranted here. Additionally these results might be weakened because of the lack of several important potential confounding factors, like dietary energy intake and physical activity.
The offspring of mothers had a history of ORD were dramatically prone to become overweight and obesity, and it was similar in children with such a paternal history, whereas at a bit lower risk. The results were scarcely reported on our inspection of other literature, and associations of family history of those ORD with childhood overweight and obesity were mostly analyzed separately. For instance, children of obese mothers showed higher risk for obesity compared with children of non-obese mothers
]. Mothers who had been diagnosed with diabetes or gestational diabetes or who received diabetes treatment were recognized significantly more likely to had overweight children
]. The reason for parental history of ORD as potential factors for childhood overweight and obesity might be mainly ascribed to the family environment and inheritance. Children`s eating patterns were substantially influenced by the caregivers, in particular mothers. The behavioral eating traits of obese parents like high-fat and/or high-calorie diet preference, excessive food intake or night snack would significantly promote the excessive weight gain of children
]. Further, the genetic factor and newly named transgenerational epigenetic inheritance may help to explain the significant impact of parental history of ORD on the development of offspring overweight and obesity
Limitation of the study
Our study have a few strength including a large sample size, using recently released WHO`s growth references, and considering a novel association between the variety of distinct aberrant birth categories and childhood overweight and obesity, especially in China. However, it was designed as a cross-sectional and retrospective study, the retrospective bias was unavoidable. It has been reported that the association between birth outcome and childhood overweight or obesity may be confounded by several potential factors, such as, parental socio-economic status, family history of obesity related disease, dietary energy intake and physical activity among childhood, etc.
]. In present study, parental educational level and career, which were firstly analyzed in the univariable analyses and the P
value were all above 0.1, were not entered into the multivariate binary logistic regression. With regard to the dietary energy intake and physical activity among childhood, they weren’t available in the study, and it is a major deficiency of our study. However, these unmeasured factors are most probably not systematically related to the outcome, but may weaken the observed association. There might be several reasons. First, we surveyed a sample size as large as more than 10,000 school children, and the self-description of dietary energy intake were usually widely different although unified measurement methods were informed, according to our experience in previous studies. Second, only a little spare time except the PE classes scheduled was spent for extra physical activity, as a result from a quite hard learning task not only in school but also at home. In addition, most of school children in Chengdu had their lunch at school almost having the same dishes. Third, one recent Chinese study indicated that the relative risk of high weight-for-length/height in children aged 1–3
years associated with macrosomia was only attenuated by 6% (odds ratios from 2.33 to 2.48) after further control for postnatal illness status and feeding modalities
]. Additionally, we had already been tracking the detailed birth information of these enrolled children in their birth hospitals, meanwhile more information about environment and life styles, as well as some laboratory and imaging index would be analyzed together in later work.