School accreditation scheme reduces childhood obesity in Hong Kong

Abstract

Childhood obesity is an increasing threat to the health of primary school students in Hong Kong. Obesity results from energy excess from food relative to energy expenditure through physical activity. In Hong Kong, a whole day primary schooling policy has been implemented since 1993 and today most primary school students have their lunch on campus and some also purchase snacks and drinks from school tuck shops or vending machines. The EatSmart School Accreditation Scheme (ESAS) aiming at combating childhood obesity was launched in 2009/2010. Professional (health promotion, dietary, programme, etc.) support is provided to help schools formulate policies, introduce structures and implement measures to help students develop the habit of healthy eating. The aim of this study is to investigate the change of childhood obesity (including overweight) rates over time among schools awarded with ESAS accreditation. Seven-year retrospective data on obesity status were obtained for the period 2007/2008–2013/2014 (number of students = 113,322, number of measurements = 314,746) from all 105 ESAS-accredited schools. Before schools were geared up for the accreditation scheme obesity rates were fairly stable (slope test p > 0.05) among their student population ranging from 23.2% to 21.9%, whereas the rates dropped significantly (slope test p < 0.05) from 21.9% to 19.3% after intervention. For ESAS-accredited schools, there was an average annual reduction of 0.49% point in obesity rate which was 0.18% point higher than that of 0.31% point among non-ESAS-accredited schools. These results show that schools achieving ESAS accreditation are associated with a bigger improvement in the student obesity problem.

Keywords

children school setting health promotion obesity/overweight nutrition

Introduction

The obesity epidemic has affected both developed and developing countries over the last few decades and is a serious public health challenge of the 21st century (1,2). The World Health Organization (WHO) estimated that in 2014, more than 1.9 billion adults were overweight; of those, over 600 million were obese. Moreover, 41 million children under the age of 5 years were overweight or obese (3). Similar to the global situation, a rising trend of childhood obesity has been observed among primary school students in Hong Kong (HK). The detection rate of obesity (including overweight) among primary students increased significantly from 16.1% in 1995/1996 to 22.2% in 2008/2009. Although this rising trend has slowed down in recent years, the overweight and obesity rate in 2013/2014 remained at a considerable level of 20.0% (4).

Health problems associated with obesity include cardiovascular diseases, insulin resistance, musculoskeletal disorders, some cancers (such as endometrial, breast, colon and advanced prostate cancer), and even disability (5,6). Childhood obesity is associated with negative physiological, psychological, and social consequences (7). It is also associated with decreased self-esteem and depressive symptoms (8).

To prevent obesity from occurring in the first place is important as obese children are more likely to become obese adults (9) and, once established, obesity is very difficult to treat (10). In addition, evidence demonstrates that prevention is a beneficial (11) and cost-effective strategy (12) for dealing with childhood obesity.

To tackle this problem, many countries have set childhood obesity prevention as a national health priority (13,14). WHO also established the high-level Commission on Ending Childhood Obesity (ECHO) in 2014 to advise on effective strategies to tackle childhood obesity in different contexts around the world. The Commission made six recommendations, one of which is to implement comprehensive programmes that promote healthy school environments, health and nutrition literacy, and physical activity in school-age children and adolescents. To implement the recommendations, it recommends that the private sector support the production of, and facilitate access to, foods and non-alcoholic beverages that contribute to a healthy diet (15).

Provision of food and drinks through lunch suppliers, canteens, tuck shops and vending machines makes school an important setting to impose a strong effect on students’ food choices and eating habits (16). In HK, more than 400 primary schools offer whole-day schooling and students spend an average of about 7 h a day at schools. (17) Most primary school students have their lunch arranged by the school on campus. Even though other students who attend half-day school may have their lunch at home, they are still able to purchase snacks and drinks from school tuck shops or vending machines.

EatSmart@school.hk (ESS) campaign and EatSmart School Accreditation Scheme (ESAS)

As an important strategy for combating childhood obesity, the Department of Health (DH) of HK collaborated with relevant government departments, education sectors, professional bodies and other community groups to launch a healthy eating promotional project called ‘the ESS Campaign’ in the school year 2006/2007 to raise public awareness and concern about healthy eating among children and to create an environment that is conducive to healthy eating in schools and the community. Riding on the Campaign, the DH and the Education Bureau have, among other initiatives, co-organised an ESAS since the school year 2009/2010 with the aim of fostering healthy eating habits among students.

The ESAS is open and offered free of charge to all primary and special schools. To qualify for ESAS accreditation, schools are encouraged to initiate and take ownership of policies, structures and practices that ultimately help students develop healthy eating habits and consume healthier food during lunch and snack time. For basic level accreditation, schools are assessed for their demonstration of commitment in providing a healthy eating school environment by laying down foundation measures covering policies, administrative measures, exercising restrictions on sale of unhealthy food items, and engagement in education and promotion on healthy eating. While for advanced level accreditation, schools must comply fully with the requirements stipulated in the DH’s latest Nutritional Guidelines on Lunch for Students (18) and/or the Nutritional Guidelines on Snacks for Students (19). The essential elements (including policy, environment, health skills and action competencies, etc.) recommended by the International Union for Health Promotion and Education had been embraced in ESAS (20). By the end of January 2015, 105 primary and special schools were accredited (ESAS-accredited schools) at either basic or advanced level, which accounted for about 16% of all 652 primary and special schools in HK.

The majority of ESAS-accredited schools (84.8%) were government or aided schools and 14.3% were special schools, while 70.8% of non-ESAS-accredited schools were government or aided schools and 7.3% were special schools. Most of the schools were operated as co-educational schools for both accredited (96.2%) and non-ESAS-accredited schools (93.8%).

Study question

In general, multi-component school-based obesity prevention programmes are more successful than single-component programmes for the prevention of childhood obesity (21). However, there is lack of evidence showing the impact of large-scale territory-wide systematic accreditation schemes including environmental modification and professional support on the change of weight status among primary school students. The aim of this study is to investigate whether there is a change in the rate of childhood obesity (including overweight) over time after schools have been awarded accreditation under the ESAS, a programme with the aforesaid features.

Methods

The Student Health Service (SHS) of the DH has been offering health assessments for HK school students. Enrolled students were given annual appointments to receive services addressing the health needs at various stages of their development. SHS covered a very high proportion (around 80% on average) of the population (more than 330,000 primary school students per year on average) under this study, making its database highly representative of the local childhood population.

Height and weight measurements for monitoring obesity patterns were carried out by well-trained health care workers following standard protocol during the annual assessment. Body weight exceeding 120% of the median weight-for-height derived from HK reference data were regarded as overweight (including obesity) (22).

Seven-year retrospective data on obesity status were obtained from SHS for the period 2007/2008–2013/2014. During this period, the total number of student visits was 681,092. After excluding students who had history of changing school, the total valid number of students and measurements from ESAS-accredited schools were 113,322 and 314,746 respectively (mean age = 9.50, 51.8% male). The total valid numbers of students and measurements from non-ESAS-accredited schools were 599,177 and 1,577,622 (mean age = 9.48, 51.9% male) respectively.

Reference period for measurements

Since schools may join the accreditation scheme at any time, their date of achieving accreditation varied. A reference period D (in days) for each body weight and height measurement conducted at the SHS centre was defined as follows:

D = Examination date - Accreditation date

Examination date was the date the student visited a SHS centre to have the obesity status recorded

Accreditation date was the date of the corresponding school obtaining ESAS accreditation

Based on the value of D, a reference period P_i is constructed and assigned to each measurement, where i refers to the number of years before or after accreditation. Take, for example, a student from school A accredited on 10 February 2012, the first measurement of this student conducted on 30 October 2011 (i.e. D = −103 days) would be recorded as P₀. The next two measurements of the same student conducted on 25 September 2012 (i.e. D = 228 days) and 15 November 2013 (i.e. D = 644 days) would be recorded as P₁ and P₂, respectively (Figure 1).

Figure 1.

Example to illustrate the definition of D and P_i.

In other words, the period P_i referred to the time period since ESAS was awarded. For those P_i with negative i value, they represent the number of years before receiving ESAS accreditation. The data for period P₅ was not included in the current analysis as the data collection period has not been completed at the time of writing this paper.

Results

Changes in obesity rate within ESAS-accredited schools

For each accreditation year, the number of students and measurements of corresponding P_i are listed in Table 1. The obesity rates were quite stable (slope test p > 0.05) ranging from 23.2% to 21.9% during the pre-intervention period from P₋₆ to P₀, whereas the rates decreased significantly (slope test p < 0.05) from 21.9% in P₀ to 19.3% in P₄ during the post-intervention period.

Table 1.

Number of students and measurements of corresponding P_i for each accreditation year.

P_i	Reference period D (years)	Total number of measurements	Number of obese measurements*	Obesity rate (%)
P₋₆	−7 to <−6 years	6383	1484	23.2
P₋₅	−6 to <−5 years	13,619	3031	22.3
P₋₄	−5 to <−4 years	23,583	5440	23.1
P₋₃	−4 to <−3 years	38,804	8714	22.5
P₋₂	−3 to <−2 years	43,447	9939	22.9
P₋₁	−2 to <−1 years	46,694	10,596	22.7
P₀	−1 to <0 year	42,285	9268	21.9
P₁	0 to <1 year	39,503	8345	21.1
P₂	1 to <2 years	30,684	6448	21.0
P₃	2 to <3 years	19,984	3953	19.8
P₄	3 to <4 years	8275	1598	19.3

In general students would only attend for SHS once within a period of 12 months, therefore the figures were very close to number of obese students.

Comparing ESAS-accredited and non-ESAS-accredited schools

To compare the changes in obesity rate with non-ESAS-accredited schools, ESAS-accredited schools were stratified by four cohorts of accreditation. As the obesity rate of post-intervention period for the schools accredited in 2013/2014 (i.e. school year 2014/2015) was not yet available, it was not included in this analysis. For schools accredited in four different school years, the reductions in obesity rates between their respective periods of ‘within 1 year before accreditation (i.e. P₀)’ and ‘school year 2012/2013’ were calculated. Hence for schools accredited in 2009/2010, we compared the differences between their P₀ and P₄; and for schools accredited in 2010/2011, we compared the differences between their P₀ and P₃, and so on. For non-ESAS-accredited schools, as they did not have reference periods P_i, the differences between the obesity rates of corresponding school years of corresponding accredited schools were calculated. For example, for comparison with schools accredited in 2009/2010, the corresponding values of non-ESAS-accredited schools were differences of obesity rate between school years 2008/2009 and 2012/2013.

Annualised reduction in obesity rate

The annual reduction of obesity rate for both ESAS-accredited schools and non-ESAS-accredited schools are shown in Figure 2 and Table 2. In general, students in ESAS-accredited schools before accreditation were comparatively more obese than those in non-ESAS-accredited schools, except for students of accredited schools in 2010/2011. The annual reduction in obesity rate among ESAS-accredited schools accredited in 2009/2010–2011/2012 ranged from 0.48% point to 0.75% point, whereas the annual reduction in obesity rate among schools accredited in 2012/2013 was 0.08% point. The average annual reduction in obesity rate among these schools accredited at four different school years was 0.49% point. These annual reductions among ESAS-accredited schools were all higher than those among non-ESAS-accredited schools of corresponding years, except for schools accredited in 2012/2013. The differences in annual reduction in obesity rate between ESAS-accredited schools accredited in 2009/2010–2011/2012 and non-ESAS-accredited schools ranged from 0.04% to 0.39% point, whereas the corresponding difference between ESAS-accredited schools accredited in 2012/2013 and non-ESAS-accredited schools was −0.04% point. The difference in average annual reduction in obesity rate between ESAS-accredited schools accredited at four different school years and non-ESAS-accredited schools was 0.18% point.

Figure 2.

Annual reduction in obesity rate for ESAS-accredited schools versus non-ESAS-accredited schools.

Table 2.

Annual reduction in obesity rate for both ESAS-accredited schools and non-ESAS-accredited schools.

Year of accreditation	Length of post-intervention period	ESAS-accredited schools									Non-ESAS-accredited schools								Effectiveness of ESAS-accredited over non-ESAS-accredited schools
		1 year before accreditation (P₀)			After accreditation				Reduction in obesity rate (before and after)	Annual reduction in obesity rate among ESAS schools (before and after)	One school year before the corresponding year of accreditation			As at school year 2012/2013			Reduction in obesity rate (before and after)	Annual reduction in obesity rate among non-ESAS schools (before and after)
		Total no. of students in ESAS schools	Total no. of obese students in ESAS schools	Obesity rate	End-point	Total no. of students in ESAS schools	Total no. of obese students in ESAS schools	Obesity rate	Reduction in obesity rate (before and after)		Total no. of students in non-ESAS schools	Total no. of obese students in non-ESAS schools	Obesity rate	Total no. of students in non-ESAS schools	Total no. of obese students in non-ESAS schools	Obesity rate	Reduction in obesity rate (before and after)		Difference in annual reduction in obesity rate
	(No. of years)	No.	No.	(%)		No.	No.	(%)	(% points)	(% points)	No.	No.	(%)	No.	No.	(%)	(% points)	(% points)	(% points)
	(a)	(b)	(c)	(d) = (c) ÷ (b)		(e)	(f)	(g) = (f) ÷ (e)	(h) = [(d) − (g)]	(i) = (h) ÷ (a)	(j)	(k)	(l) = (k) ÷ (j)	(m)	(n)	(o) = (n) ÷ (m)	(p) = [(l) − (o)]	(q) = (p) ÷ (a)	(r) = [(i) − (q)]
2009/2010	4	5363	1201	22.39	P₄	4451	864	19.41	2.98	0.75	241,203	53,325	22.11	207,789	42,991	20.69	1.42	0.35	0.39
2010/2011	3	11,620	2474	21.29	P₃	10,865	2156	19.84	1.45	0.48	229,133	50,455	22.02	207,789	42,991	20.69	1.33	0.44	0.04
2011/2012	2	10,097	2338	23.16	P₂	10,502	2297	21.87	1.28	0.64	216,671	46,123	21.29	207,789	42,991	20.69	0.60	0.30	0.34
2012/2013	1	7022	1493	21.26	P₁	7295	1545	21.18	0.08	0.08	211,286	43,979	20.81	207,789	42,991	20.69	0.13	0.13	−0.04
Overall obesity rate				22.01				20.72					21.58			20.69
Reduction in overall obesity rate (% point)									1.29	0.49							0.89	0.31	0.18

Discussion

This paper summarises the first 4 years effects of a territory-wide, comprehensive, and multi-pronged school-based accreditation scheme with policy and environmental components on reduction of childhood obesity rate in HK. In general, ESAS-accredited schools performed better than non-ESAS-accredited schools in lowering obesity rates, indicated by the higher annual reduction in obesity rates when comparing with non-ESAS-accredited schools. A separate study reveals that various aspects of students, parents and schools from ESAS-accredited schools performed significantly better in the aspects of knowledge and attitude towards healthy eating than those from general schools (23). It is worth noting that non-ESAS-accredited schools also recorded reduction in obesity rates among their students during the study period. This might be due to the effect of overall promotion of healthy lifestyle, including healthy eating in the community. For example, the ‘EatSmart @restaurant.hk’ campaign is another major health promotion programme of the DH for promoting healthy dishes in food premises. Participating restaurants, through taking part in the campaign, master the basic knowledge of food nutrition and techniques of healthy cooking, and apply them to produce dishes with better nutritional quality to customers (24). Moreover, lunch suppliers serving the ESAS-accredited schools tend to offer the same healthy lunch choices to non-ESAS accredited schools using the same production lines to supply meals to non-ESAS accredited schools. This overall reduction in obesity rate in non-ESAS-accredited schools might also explain why the decrease in the first year of obesity rate in schools accredited in 2012/2013 was less than the non-ESAS-accredited schools. More time would be needed to monitor the effect of accreditation in obesity rate in 2012/2013 accredited schools.

Though ESAS has achieved seemingly remarkable results, it is worth noting that neither single interventions nor short-lived promotions alone confined to a particular setting will be sufficient to reverse the increasing trend of childhood obesity (25). Evidence suggests that adopting comprehensive strategies might be a more feasible solution (26). Collaboration and partnership with staff, students, parents as well as major stakeholders are key contributory factors to the positive outcomes of ESAS (27).

There were a few limitations to this study. While the coverage rate of the SHS programme was very high (around 80%) for primary school students, characteristics of students who did not attend SHS could not be elucidated. At the same time, schools’ participation in ESAS was on a voluntary basis. It was not clear if the ESAS-accredited schools were more health-conscious and willing to foster a nutrition-friendly school environment than non-ESAS-accredited schools. Short of a randomised trial, it would not be feasible to identify a group of ‘control’ schools with the same attributes (e.g. as enthusiastic in healthy eating promotion) but without the intervention.

Moreover, ESAS-accredited schools represented a biased sample as they had different demographics from primary schools in the population. Only 1% of ESAS-accredited schools were private/direct subsidy scheme (DSS) schools, students of which come mainly from higher socioeconomic classes as they have to pay for a higher annual school fees, while 22% of non-ESAS-accredited schools were private/DSS schools. Coupled with the fact that more ESAS schools are government or aided schools than non-ESAS accredited schools (84.8% vs. 70.8%), the participation of schools in ESAS does not favour schools from higher socioeconomic class. In addition, the composition of students in all schools changed yearly because some year 6 students will leave the school after graduation, while year 1 new students will join the school in the next school year. The effects of these differences in characteristics of students were difficult to be assessed. For future studies, it is recommended to collect more socioeconomic data for analysis to see if there may be any differential effects on children by socioeconomic status.

Before and during the intervention period, the ESS campaign was ongoing, as well as many other school-based healthy eating promotional projects initiated by community organisations or schools themselves. It is possible that these promotional efforts have spillover effects on some schools resulting in overall reduction in obesity rate, observable among ESAS and non-ESAS accredited schools, making the difference between the groups smaller and less observable on the one hand, or causing the perceived difference to be a spurious observation.

As the study was not a randomised control trial, causal attribution of ESAS programme on the drop in childhood obesity cannot be concluded. Neither is it possible to infer whether accreditation and reduction in student obesity were both the outcome of certain attributes or actions taking place in the schools that are not described in this study. It should be noted that the P_i calculated for ESAS-accredited schools might not be directly comparable statistically with annual obesity rates of non-ESAS-accredited schools. Nevertheless, comparison between two groups produced an observable intervention effect of ESAS programme on reduction of childhood obesity rate.

The global prevalence of overweight and obesity in children aged under 5 years has increased from around 5% in 2000 to 6.3% in 2013, and it is estimated that the prevalence will rise to 11% worldwide by 2025 if current trends continue (28). Nevertheless, the prevalence of childhood obesity declined in some countries over the past several years, especially for preschool children. For example, data from Centers for Disease Control and Prevention showed a significant decrease in obesity among children aged 2–5 years in the USA, dropping from 14% in 2003–2004, to around 8% in 2011–2012 (29). The decreasing trend was also found in France (1). Although the reasons for the decreasing trend in childhood obesity rates are still not clear for these countries, our current study showed that a comprehensive, and multi-pronged school-based accreditation scheme with policy and nutritional environmental components such as provision of healthy lunch and snacks, may be one of the contributors to the decreasing trend. ESAS offered an intervention relevant to the school setting that is more than simply a health educational programme. The ESAS works best when schools, irrespective of the social economic background of students, share the same ethos of enriching students’ lives through creating healthy sustainable environments for growth and development.

Conclusion

Results from this study revealed that the obesity rate of students from schools taking part and accredited under the ESAS programme decreased after the intervention more significantly than students from non-ESAS-accredited schools. Given the current burden of health conditions, including obesity, related to unhealthy diets, schools should play a more active role in creating a nutritionally sound and friendly environment for students. The ESAS programme is a promising intervention that should be implemented and institutionalized more widely across local schools to control the childhood obesity problem. The programme’s longer term effect on children’s health should be continuously monitored.

Footnotes

Conflict of interest

The authors declare that there is no conflict of interest.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

ORCID iD

Kit Ching To

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