A policy-driven multifaceted approach for early childhood physical fitness promotion: impacts on body composition and physical fitness in young Chinese children

There is an emerging epidemic of obesity in young children age below 5 years old in both the developed and developing countries [1, 2]. Recent national and regional data have consistently shown that the prevalence of obesity in young Chinese children has dramatically increased while fitness measures showed declines since 1980s [3–6]. One study of children in nine large Chinese cities found that the prevalence of obesity in 5 years-old increased from 0.84% in 1986 to 6.05% in 2006, a rate of annual absolute increase at 0.26 percentage point [3]. Recent studies reported prevalence of obesity ranging from 8.4% to 10.5% in preschool children living in large Chinese metropolitan cities [7, 8].

According to the 2010 Chinese National Fitness Survey, weight and height of Chinese children aged 3 to 6 years old increased significantly from 2005 to 2010. However, the increase was greatest in weight and Body Mass Index (BMI) and less in height. The survey also revealed that the average National Physical Fitness Index decreased 0.36 percentage points from 2005 to 2010. This trend was also reflected in preschool children with declines in some physical fitness measures (e.g. 20-meter agility run, broad jump, walking on balance beam) [9].

There is an important connection between body growth and physical fitness [10]. Optimal growth is accompanied by healthy body composition characterized by lower level of fat mass and higher level of fat free lean mass (muscles and bone). High level of physical fitness is closely associated with healthy body composition and lower body fat percent in children [11, 12]. Participation in physical activities, especially moderate and vigorous physical activity (MVPA), can improve physical fitness and body composition in children [11]. An inverse relationship between levels of obesity and measures of physical fitness was reported recently in a large sample of 6–12 years old Chinese children [13].

Preschool children are surprisingly sedentary and spend more than half of their waking hours being sedentary [14, 15]. A recent meta-analysis of 29 studies of preschoolers aged 3–5 conducted in developed countries found that the average of MVPA was 42.8minutes (min)/day(d) [16]. Furthermore, young obese children tend to be less active [17, 18] who have lower level of fundamental movement skills [19–21] compared to their normal weight peers. Therefore, effective strategies for promoting MVPA and fundamental movement skills, and reducing sedentary behavior are urgently needed for preschool children [22–24]. There is little data on the amount of physical activity (PA) engaged by preschool Chinese children at the present time. Current regulations of childcare in China require the provision of outdoor play opportunities, play equipment and playground but lack specifics on the amount of activity time and frequency [25].

There is a consensus that multi-component interventions hold the most promise to curtail childhood obesity when both physical activity (PA) and diet are targeted at childcare and/or home [22, 26, 27]. However, obesity interventions targeted physical activity and physical fitness in children are often preferred since they are relatively straightforward mediators of energy balance and physical growth and pose no known harms [10, 28–30]. Dietary interventions are more complex and difficult to implement partly due to the cost of healthier foods and food service regulations [27] and partly due to the fact that children are growing at fast rate and restrictive diet may lead to under-nutrition or malnutrition [31]. This is particular challenging in the developing countries where malnutrition and quality of nutrients in foods are still concerns. Nonetheless, promotion of portion control and intake of fruits and vegetables and reduction of sugar drinks and energy-dense snacks have been linked to success in preventing excessive weight gain, and are recommended strategies for preschool children [32]. Family support and engagement play key roles in developing healthy eating and activity habits in young children. [32, 33]. Interventions that targeted both childcare and home have led to more changes in PA and healthy eating, comparing to focusing only on childcare or home [34–36]. Finally, recent reviews have pointed to the need for policy and environmental change studies of early childhood obesity prevention [33, 37]. Among the top priorities identified for study are PA policy changes, teacher training in PA, modifications of play format and equipment, engagement of parents, and parent support [27, 33, 38].

Rapid economic growth in China has led to changes in lifestyle and living conditions, especially in urban regions, in the last few decades [39]. These changes have created an obesogenic environment in large metropolitan regions in China that have reported highest prevalence of obesity in all age groups [4, 9]. The correlates of obesity in Chinese children are similar to those reported in studies conducted in other countries, including family background (family income, parent education, parent weight status), birth weight, breastfeeding, physical activity, physical fitness, screen time, diet, access to physical activity and healthy foods, and regions of residence [28, 29, 40–42]. Obesity preventions targeting these correlates in Chinese children and adolescents have showed promising results [43]. Presently, research is sparse on effective strategies to prevent obesity in preschool children in China. Given the enormity of health and economic consequences of obesity [40, 44], there is an urgent need to explore policy and environmental approaches that can address the challenges in combating the obesity epidemic in China. In this paper, we presented the findings of a multifaceted intervention study conducted in childcare centers for preschool children (3–5 years of age) in China. The purposes of the study were 1) to test the effects of the intervention on healthy weight growth (body composition) and physical fitness in preschool Chinese children, and 2) to evaluate the feasibility of conducting a complex health promotion campaign in childcare setting.

Findings from this study demonstrated that a multi-faceted intervention can improve preschool children’s body composition and physical fitness. Children in the intervention center had less gains in body fat percent (−1.35%) and fat mass (−0.55 kg) and more gain in muscle mass (+0.48 kg) and total body weight (+0.36 kg) than the children in the control center. The additional gain in body weight (+0.43 kg) may be attributed to the increase in bone content in the intervention children although it was not assessed in the study. However, it should be noted that there was no significant differences in BMI and BMI z-scores between intervention and control children. As all preschool children are expected to grow taller and heavier, the intervention clearly promoted the development of fat free soft tissues and prevented excessive weight gain. This is similar to the results of a physical activity intervention study that significantly reduced body fat percent, and increased fat free mass and bone density but increased body weight and BMI in elementary school children [63, 64]. The body composition in that study was assessed by Dual-energy X-ray absorptiometry. Both study used a robust physical activity intervention that may account for “the healthy” weight gain in intervention children with more fat free soft tissues and less fat mass [31]. The present study added 28 minutes of MVPA in intervention children on weekdays and 18 minutes of MVPA on weekend days. A Swedish study also reported an increase in physical fitness and decrease in skinfolds in elementary school children in a 1-year physical activity intervention study [56]. The Framingham Children's Study tracked physical activity by accelerometry and body fat by triceps and subscapular skinfolds in preschool children aged 3 to 5 years from preschool to the first grade in school and found that active preschool children gained significantly less fat compared to inactive children after controlling television viewing, energy intake, baseline triceps, and parents' body mass index [65]. The 2011 Cochrane review on childhood obesity prevention reported an average reduction of 0.26 kg/m² in children aged 0–5 years from 5 RCTs, conducted mostly in the developed countries [26]. The impact on BMI appeared to be the strongest in the youngest children than those aged 6–12 years and 13–18 [26]. A recently completed community-based multi-setting and multi-strategy obesity prevention intervention significantly lowered weight, BMI, BMI z-score, and prevalence of overweight/obesity in subsamples of 2 to 3.5 years old Australian children [66]. The finding of impact on body composition from this study adds to the literature on this important topic.

The intervention significantly increased the performances in 20-meter agility run, broad jump, tennis ball throwing, sit and reach, balance beam walk, and 20-meter crawl in intervention children. These measures are manifestations of children’s fundamental movement skills and movement capabilities [6]. Few obesity prevention studies measured their impacts on physical fitness in young children [67]. A large randomized trial with Scottish preschool children found that a physical activity intervention significantly improved fundamental movement skills but had no impact on weight and BMI [68]. The authors attributed the lack of effects on weight and BMI to inadequate dose of physical activity. Significant improvement in fundamental movement skills was also reported in low-income preschool children who were exposed to gross motor activity interventions in the United States [34, 38]. The improvement in physical fitness measures in this study was attributed to the provision of physical activity programs (70–100 minutes daily at the center) that incorporated age-appropriate fundamental movement skills and gross motor activities with moderate and vigorous intensity [69–71]. The quality of outdoor play was further enhanced by innovative, soft and portable playgroup equipment designed specifically to meet the developmental needs of fundamental movement skills for preschool children [51, 52]. Similar findings have also been reported in older children who were exposed to MVPA intervention [11, 72].

The results of the process evaluation suggested that the policy and environmental changes at childcare center may account for the enhancement of teacher’s ability in implementing the outdoor curriculum increased the amount of MVPA, nutritional quality of food services, produced supportive environment for physical activity and healthy eating in preschool children. These changes have been identified as effective strategies for childhood obesity prevention by the recent Cochrane review [26] and others [33, 38]. Policy and environmental interventions in childcare setting in the United States [73] and Australia [74, 75] have led to changes in children’s play behaviors, increase in structured play time, and improvement in teacher training. Intervention with parents was successful and well received as indicated by high level of participation. The family intervention increased parental support and engagement [76, 77]. and modeling [78] that encouraged children to be more active at home. The environmental changes, such as playground renovation and health promotion events in intervention community can contribute to increased access to physical activity opportunities and health education in the community [33], although we did not collect information on the use and attendance of study participants to affirm the potential impact of the community-based intervention.

The study has several strengths that increased the internal validity of the study. First, we received full cooperation and participation from the center administration and staff to implement our proposed policy and environmental changes which provided unique opportunity to test their impacts. High fidelity of implementation was the results of this support and cooperation. Secondly, the uses of validated age-appropriate outcome measures were critical to accurately assess the impacts of the study in young study participants. For example, without the use of the bioimpedance analyzer, we will not be able to observe the favorable changes of body composition, i.e. decreased body fat percent and increased muscle mass, in the intervention children [79]. Third, we took consideration of children’s age, developmental needs and environmental barriers in designing intervention activities [26, 27]. As a result, all children benefited similarly, regardless their gender and grade level.

There were limitations in the study design that warrant cautions in interpreting the study findings. The study had a small sample size and used a non-randomized study design with two conveniently selected childcare centers. We tried to minimize the threat of selection bias to the study validity by using a control center that matched the intervention center in demographics and quality of the facilities and teachers. Compared to the physical activity intervention, we had a modest intensity nutrition intervention with food service workers and parents and did not have direct nutrition education to the children. Nutrition education with children can increased healthy eating behaviors in preschool children and should be included in future [27]. We only collected limited dietary data (food preparation records) which hindered the understanding of the impact on dietary behaviors. No valid dietary measure was available for preschool age Chinese children [80]. Changes in parental physical activity were based on self-report and need to be validated in the future. Finally, we did not conduct long-term follow-up to examine the sustainability of the study impacts on the children and the facility.

We conclude that the policy-driven multi-faceted intervention, that were designed to target physical activity and diet behaviors of preschool children, significantly improved preschool children’s body composition and physical fitness. The design of the intervention has taken many of the research priorities identified in the literature. To our knowledge, this was the first such study in China. The intervention program was effective to engage children, childcare center staff, families, and community in an integrated effort to promote physical fitness and healthy eating by link policy and environmental changes, physical and health education and health promotion in childcare setting. Findings from this study may contribute to the understanding of intervention design and curriculum development in early childhood obesity prevention in China and other countries in similar stages of economic development and societal changes [30]. Although it is not expected that our intervention program can be adopted in whole by any community or school system, the findings from this study can be informative for health professionals and researchers in formulating intervention in early childhood obesity prevention. We plan to make the outdoor play curriculum and intervention materials designed for the study available for others to replicate the study. The intervention program should be tested for efficacy as well as cost-effectiveness in a randomized trial.