Epidemiology of childhood overweight & obesity in India: A systematic review

The term overweight refers to excess body weight for a particular height whereas the term obesity is used to define excess body fat1. Overweight and obesity primarily happen either due to excess calorie intake or insufficient physical activity or both. Furthermore, various genetic, behavioural, and environmental factors play a role in its pathogenesis. Childhood obesity is a forerunner of metabolic syndrome, poor physical health, mental disorders, respiratory problems and glucose intolerance, all of which can track into adulthood2. Developing countries like India have a unique problem of ‘double burden’ wherein at one end of the spectrum we have obesity in children and adolescents while at the other end we have malnutrition and underweight.

Globally, the prevalence of childhood obesity has risen in recent years. The International Association for the Study of Obesity (IASO) and International Obesity Task Force (IOTF) estimate that 200 million school children are either overweight or obese3. It is difficult to compare prevalence rates of childhood obesity in different countries due to several limitations: lack of nationally representative surveys of school children and paucity of serial measurements over time. Ogden et al4 reported that the percentage of obese children in the US (6-11 yr age group) was 7 per cent in 1980 which increased to 20 per cent by 2008. Parallely, among adolescents (age groups of 12-19 yr) obesity rates increased from 5 to 18 per cent. Recent figures from the IOTF website3 showed prevalence rates of overweight/obesity as 40 per cent in both genders in US. Studies conducted on childhood obesity suggest that it may be plateauing off in some developed countries, while steep increases continue to occur in developing countries56. However, these trends are not well documented.

Lower BMI (body mass index) cut-offs of 23 and 25 kg/m² have been suggested by the World Health Organization (WHO) and IOTF for Asian Indian adults for overweight and obesity, respectively78 but these are not applicable for children and adolescents. Over the years, there has been a lack of consensus on the various cut-points or definitions used to classify obesity and overweight in children and adolescents. This makes it difficult to interpret and compare the global or national prevalence rates910. For children and adolescents, overweight and obesity are usually defined using age and gender specific normograms of BMI.

There is lack of national representative data on obesity in children from India with its widely varying geographical, social and cultural norms. Here we attempt to review available literature on childhood overweight and obesity from India using the various cut-points used to define childhood and adolescent obesity. We also used the published data from India from 1981 to 2013 to plot the trend in childhood obesity and to look at its key socio-demographic patterns.

Material & Methods

A review of the studies published in the last three decades between 1980 and 2013 reporting on prevalence of childhood overweight and obesity (age 1-18 yr) in India was conducted using a systematic approach. As the aim was to present the current scenario in this area, we restricted our search to 1980 and beyond. Literature search was done in available scientific public domains such as Google Scholar, PubMed, IndMED and Cochrane systematic reviews using key words such as childhood and adolescent overweight, childhood obesity, epidemiology in India and globally, body mass index (BMI), trend and prevalence. A combination of MeSH terms and free texts was used for the search. Cross references from identified articles were also used to expand the coverage. Also, websites of official agencies such as IOTF, WHO and Centres for Disease Control and Prevention (CDC) were accessed for related information. The review search initially revealed 612 titles or abstracts. The first two authors critically reviewed the studies to decide if these could be included based on the criteria detailed in the flow chart indicating the review process (Fig. 1). Prevalence in the age group of 1-5 yr were obtained only from national surveys; most studies from India reported only on undernutrition in this age group. Finally, 52 studies were selected and were grouped based on the age groups studied and presented as childhood (1-12 yr), adolescent (10-18 yr) and childhood and adolescent (studies inclusive of both age groups) obesity trends in India according to the year in which that study was published. All reported prevalences were taken directly from the study and no recalculations were performed. Due to the lower obesity prevalence rates in rural or government schools, these were excluded only from the trend analysis (Fig. 2) but have been reported in the Tables. Thus, to plot the figure demonstrating combined childhood and adolescent obesity trends, only urban prevalences from 42 studies (49 datasets as 7 studies reported multiple datasets in the form of repeat surveys) from 1981 to 2013 were used and the year the study was conducted in was considered for analysis; in case, this was not mentioned, the publication year was included.

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Fig. 1

Flow chart indicative of the review process.

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Fig. 2

Box plots indicating overweight (a), obesity (b) and combined (c) trends in Indian children and adolescents (1981-2013).

Source: Refs 91011121314151617181920212223242526272829303132333435363738394041424344454647484950

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For each time period, the median of the reported values for the individual studies was calculated along with the quartile limits. Trends for overweight, obesity and combined prevalence in children and adolescents were calculated and presented using box plots (Fig. 2). The box plot included the 25^th and 75^th percentiles and data labels plotted were median values with the minimum and maximum. When multiple cut-offs were used in the same study, only IOTF-Cole et al 2000 criteria51 were considered to prevent duplication of study data. Also, two outliers5253 were not included in this trend analysis but shown in Table I. We further looked at the distribution of prevalence of obesity by sex and area of residence (rural/urban).

Table I Childhood (1-12 yr) obesity trends in India

Prior to 2001, prevalence studies reported more on obesity (5 studies) rather than overweight (2 studies) while post-2001, there were almost equal numbers of reported values for both (45 for obesity versus 41 for overweight). Due to this drop in the sample size and number of studies conducted, plotting separate trend graphs for children and adolescents did not show a good trend. Therefore, the results are presented for all 52 studies combined with a total count of 435162 participants. Overweight numbers were available for 43 studies comprising 353738 participants while obesity numbers were reported for 50 studies with 431262 participants. Both numbers were available for 42 studies with 351454 participants. The combined prevalence was the sum of the overweight and obesity prevalence.

Results

Overall, 52 studies were included based on the defined inclusion and exclusion criteria (Fig. 1). The geographical spread of these studies is shown in Fig. 3. The studies appear to be spread across the country with 16 of 28 States being covered by at least one survey. Fig. 3 shows the lack of prevalence data on childhood obesity from many northern and north-eastern States of India.

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Fig. 3

Map of India indicating prevalence (%) of childhood obesity in various States and cities. Values in parentheses are prevalence in percentages. Source: Refs 9101112131415, 171819202122232425262728293031323334353637383940414243444546474849, 52, 53, 6465666768697071.

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Epidemiology of childhood obesity: Indian data

Studies reporting prevalence of childhood and adolescent obesity in India were included as part of Table I (1-12 yr), Table II (10-17 yr) and Table III (combined age group) in accordance to the year the study was published.

Table II Adolescent (10-18 yr)^# obesity trends in India

Table III Childhood & adolescent obesity trends in India (Studies inclusive of both age groups)

Children (Table I): The key studies are from the National Family Health Surveys (NFHS) and National Nutrition Monitoring Bureau (NNMB) surveys5455565758. These surveys covered under-five children only. In the older age groups, the study by Preetam et al11 from Puducherry was the largest. In under-fives the prevalence of obesity was below 2 per cent in all the studies. In children above 5 yr, the prevalence of obesity varied between 2 to 8 per cent. Overweight rates were around two times higher and seem to be more in northern and eastern India than in southern India. One study from Srinagar52 reported a high prevalence rate of 25 per cent, probably due to the smaller numbers studied and being from affluent families.

Adolescent (Table II): The largest study in this age group was the Global School Based survey in 2007 on 8130 students. Overall, overweight prevalence varied between 3 to 24.7 per cent and obesity ranged from 1.5 to 14 per cent in these 28 studies highlighting the wide variability in their prevalence in India. In most studies, slightly higher prevalence rates were reported in boys, compared to girls.

Combined (Table III): A total of 17 studies reported prevalence of overweight/obesity in childhood and adolescence but were combined in such a way that we could not separate the two. The least prevalence of obesity was reported from Nagaland (2.3%) and the maximum from New Delhi (29%) and both used the IOTF-Cole et al criteria51.

Discussion

India is a fast growing economy, currently undergoing major epidemiological, nutritional and demographic transitions. These transitions tend to promote obesity in all age groups. However, when one looks at the prevalence of obesity alone, there is no clear secular trend. The median values ranged from 5.5 per cent in 2001-2005 to 4.0 per cent in 2006-2010 and then rose to 4.6 per cent since 2010. This suggests that the prevalence of obesity has probably been somewhat constant over the last couple of decades. However, the overweight and combined overweight/obesity prevalence showed an increasing trend. The prevalence of overweight increased from 9.7 per cent prior to 2001 to 13.9 per cent in studies reported after 2010. The combined trend followed a similar pattern increasing from 15.9 per cent prior to 2001 to 16.3 per cent from 2001-2005. The value then increased to 17.4 per cent in the 2006-2010 period, finally reaching 19.3 per cent in studies reported after 2010. Hence, there was a trend of increase in overweight among children/adolescents in India.

The criteria used for diagnosis of obesity in children and adolescents in developing countries like India have been based on American and European BMI standards51. In these standards, the >85^th percentile for overweight and > 95^th percentile for obesity have been derived from the data from National Center for Health Statistics (NCHS)60 and National Health and Nutrition Examination Survey (NHANES)79 in USA or from studies in western European countries where BMI > 95^th percentile corresponds to >130 per cent ideal body weight and BMI of > 30 kg/m²(Ref 8). The CDC growth curves have been developed from an apparently overweight population80. In an effort to overcome this drawback, Cole et al51 used data from several European and Asian countries to determine childhood BMI cut-points that corresponded to adult BMI of 25 and 30 kg/m². Many countries including India use the Cole (2000) criteria. This criterion has also been adopted by the IOTF. However, two studies conducted in India6681 showed the IOTF reference classified participants as having a lower weight. Both the studies concluded that the Cole criteria were not suitable for Indian and South Asian children.

The WHO has been persuading paediatricians and governments all over the world to use the WHO growth charts for identifying underweight and overweight80. de Onis and group82 thus came up with the WHO 2007 age and gender specific BMI cut-offs as a global standard. In children selected from across the globe it was seen that they grew at an astonishingly consistent pattern up to the age of five years, suggesting that there may not be ethnic differences in the growth pattern of babies and children83. However, it is likely that the WHO cut-off will result in higher overweight and or obesity rates1780.

Conclusions

The present analysis shows that overweight and obesity rates in children and adolescents are increasing not just among the higher socio-economic groups but also in the lower income groups where underweight still remains a major concern. This suggests the need for a balanced and sensitive approach addressing economic and nutrition transitions to effectively tackle this double burden paradox in India.