Overweight and Obesity Prevalence in Young Children Living in Athens

Fotini Venetsanou, PhD

Assistant Professor, School of Physical Education and Sport Science, National and Kapodistrian, University of Athens, Ethnikis Antistasis 41, Dafni 17237, Athens, Greece; E-mail: fvenetsanou@phed.uoa.gr

INTRODUCTION

In recent decades, the prevalence of obesity has reached alarming levels worldwide,^1,2 having affected not only adults^3,4 but also children.^5,6 There are several studies reporting an upward trend of childhood obesity over the years in several countries, like New Zealand,⁷ USA,⁸ Brazil,⁹ China¹⁰ and Taiwan.¹¹ This global trend has affected European countries too,^10,12,13 with the British islands and the countries in the Mediterranean region presenting the highest rates of overweight and obesity in pre-school age.¹⁴

The increase in the prevalence of obesity is considered to be due to changes in environmental factors, such as poor nutrition¹⁵; increase in the calorie intake and physical inactivity^16,17,18; prolonged television watching^19,20; working and playing on computer²⁰; family socio-economic status^7,21,22; parental body mass index (BMI)^2,23,24 and parental separation.²⁵

Childhood obesity is associated with a wide range of serious health complications, such as cardiovascular disease²⁶ and metabolic abnormalities,^27,28,29 while it is thought to influence social and psychological functioning³⁰ and be associated with low self-esteem, depression and bullying at school.³¹ Moreover, several longitudinal studies have revealed that children’s BMI levels track to adulthood,^26,32,33,34 with approximately 70% of children who are obese between 6 to10 years of age to remain obese in their adulthood.³⁵ 

Due to the aforementioned negative consequences on children’s life quality, the epidemiological aspects of childhood obesity have strongly worried the research community,³⁶ while many countries have set childhood obesity as a major public health issue.^37,38 A positive result of the society’s sensitivity on the issue of obesity, given the several recent research findings, may be the likelihood of decrease^39,40 or stabilization in childhood obesity prevalence.^{6,14,41,42,43}

Greece is a small country in the Mediterranean region facing the problem of obesity.³⁸ Moreover in the last decade, the country undergoes a financial crisis that may have affected childhood obesity prevalence, through changes in children’s dietary habits.⁴⁴ However, in the last decade, very few studies investigating obesity prevalence in pre-school or older children have been conducted in Greece. To our knowledge, there are only three studies focusing on pre-school children (one of them, published in two papers), that report high percentage (21.2-23.2%) of overweight (including obesity).^19,23,45,46 As far as older Greek children are concerned, prevalence of overweight (including obesity) among 6- to 12-year-olds was found to be 31.2%⁴⁷ and among 8- to 9-year-olds ranged from 30%^48,49 to 38.3 %.⁵⁰ Moreover, a higher percentage (40%) was found in 10- to 12-year-old Greeks.^51,52

Taking into consideration that childhood and adolescence seem to be the most critical periods for the development of obesity,⁵³ as well as that obesity appears to occur as early as children enter kindergarten⁵⁴ and it is difficult to reverse in older children and adults,⁵⁵ its timely prevention is of great importance. The first step for the development of effective prevention and intervention programs is the estimation of current obesity levels and the understanding of its trends. Regarding Greece, as it was noted above, there is insufficient scientific evidence regarding obesity prevalence in young children. Such evidence would be valuable if national/municipal policies against childhood obesity are to be planned and implemented. Thus, the aim of the present cross-sectional study was to assess overweight and obesity status in young children living in the capital of Greece, Athens.

MATERIALS AND METHODS

Seven hundred and fifty-two randomly selected children (320 boys; 432 girls), aged 4-8 years (6.37±1.17 years) volunteered to participate in this study (response rate 85%). All the participants lived in Athens, the capital of Greece. Their parents (or legal guardians) signed a written informed consent before children’s participation in the study, which was conducted in accordance with the Helsinki Declaration.

Anthropometric data as well as data for age and gender were collected by trained physical educators between October 2014 and May 2016. Body mass measurement was conducted with an electronic scale to the nearest 100 gr (Beam Balance 710, Seca). Standing height measurement was performed with a Stadiometer to the nearest 0.5 cm (Stadiometer 208, Seca). The above measurements were conducted in the morning, with participants barefooted and lightly dressed. BMI was calculated by dividing each participant’s weight (in kg) by the square of standing body height (in m²). Overweight and obesity definition was based on the International Obesity Task Force (IOTF) gender- and age-specific cut-off criteria.^56,57 

For the statistical analyses, participants were divided into four groups according to their age (4-5, 5-6, 6-7 and 7-8-year-old) and chi-square tests were used, with statistical significance set at α=0.05. Statistical analyses were performed using IBM SPSS Statistics 22.0.

RESULTS

Anthropometric characteristics of boys and girls, by age groups are presented in Table 1.

According to the cut-offs of the IOTF, the overall prevalence of overweight was 18.2% (18.1% for boys and 18.3% for girls) and that of obesity was 7.4% (5.6% for boys and 8.8% for girls). Prevalence of overweight and obesity in both genders by age groups are presented in Figure 1.

Figure 1. Prevalence of Overweight and Obesity in Greek 4- to 8-Year-Old Boys (Left Part) and Girls (Right Part).

The prevalence of overweight and obesity in girls was increasing with age in pre-school years, whereas a decrease with age was observed in the first school years. Specifically, in 4- to 6-year-old girls, the prevalence of overweight and obesity were 19.3% and 10.5%, respectively, while in 7-8 years, the corresponding rates were 16.9% and 8.5%, respectively. In boys, on the other hand, a higher percentage of obesity and overweight prevalence was found in 7- and 8-year-old (24% overweight and 11% obese) than in 4- to 6-year-old (15.5% and 3.2%, respectively).

In the overall sample, there were no significant differences in prevalence of overweight and obesity between boys and girls (χ²=2.76, p=0.25). The same result was revealed after combining overweight and obese into the same category (χ²=1.07, p=0.30). As far as overweight and obesity prevalence among age groups is concerned, in girls there were no significant differences, while in boys, significant differences were found between 6- and 7-year-old (Table 2).

DISCUSSION

The present study attempted to provide current information for the prevalence of overweight and obesity among young children in Athens, the capital of Greece. The selected age group was spread into four successive years (4- to 8-year-old) and covered pre-school and first years of schooling periods. These particular periods in children’s life have not been, adequately, investigated in Greece, even though a dramatic upraise of pre-school obesity since 1990, with the prediction to climb higher during the current decade, has been indicated at an international level.⁵⁸

As it has been highlighted by earlier studies, the younger part of Greek society has been underwent a consistent increase in overweight/obesity prevalence during the previous decades.^59,60 According to the present results, a relatively high overall percentage for overweight (18.2%) and obesity (7.4%) is evident, especially in comparison to the considerably lower obesity rate of 3.6% found as early as 1990-1991 in the age group of 6- to 17-year-old Greek youths.⁶¹ This finding comes to reaffirm the trend of increase, in relation to children’s obesity, in Greece.

However, in order to evaluate the results of this study and draw conclusions on the current situation on overweight/obesity, a comparison with recent national and international findings would be informative. It is useful to note, at this point, that such comparisons should be carefully made, as often lead to misconceptions caused by discrepancies in methodology between different studies.¹⁴ A common difference observed is the criteria used for BMI classification to overweight/obesity categories (e.g., IOTF, World Health Organization/WHO, US Centers for Disease Control and Prevention/CDC or other national standards), which usually result in different estimations for the relevant overweight/obesity rates.^7,10 As IOTF cut-off criteria have been adopted by this study, comparisons will only be made with works that followed the same procedure.

Comparing the present results with those of previous studies conducted in Greece, it was revealed that the current obesity rate of 7.4% was almost identical to that of 7.3% indicated by Kyriazis et al⁴⁷ and within the range of prevalence (5.8%-11.7%), reported in other studies.^{45,48,49,51,52,60} Considering overweight and obesity prevalence as a whole, the present findings regarding pre-school aged children (24%) are slightly higher than those of previous studies.^23,45,46 Concerning older children (6-8-year-old), in the present study, an overweight/obesity prevalence of 29.7% was found. This is similar to the percentage found by Kollias et al^48,49  in children of 9 years of age (30%) and Kyriazis et al⁴⁷ in children 6- to 12-year-old (31.2%); however, it is much higher than the prevalence revealed in the study of Georgiadis and Nassis⁶¹ (20.9%) that was conducted in early 1990s. It seems that childhood obesity remains a public health issue for Greece.

In addition, it would be of great interest to understand the differences that are supposed to occur in respect to gender, as well as, how adiposity develops within different age groups. In relation to gender, no significant differences observed in this study (overall percentage: overweight, 18.1% for boys and 18.3% for girls; obesity, 5.6% for boys and 8.8% for girls), a finding that is in accordance with other studies.^6,23,46,62 Nevertheless, gender is a complex factor, controversially associated with overweight/obesity trends.^{13,16,20,45,63} In reference to that, and since both genders present high risk to obesity pathogenesis, boys and girls should be equally protected by its adverse outcomes.

Furthermore, in order to get additional information on overweight/obesity development, it seems challenging to study smaller age groups and observe potential trends between them.  In the present study, four age groups were identified (4-5, 5-6, 6-7 and 7-8-year-old) and individually analyzed. According to the results, there was only one statistically significant difference in overweight prevalence (including obesity) among age groups; that was between 6- and 7- year old boys, with the 7-year-old surpassing the 6-year-old. Unfortunately, there is no data to directly compare and further support this finding, because of the different, usually broader age groups other studies utilized. The acknowledgement that the first years of schooling are an important crossover in child’s life is valuable. Special attention should be given at this period on the dietary and physical activity patterns of children, since these two factors are proposed as anti-obesity measures.^16,48,52,64 Taken together the fact, that obesity early in life possibly results in obesity later in life,³² children should be encouraged to eliminate screen time^19,47 and establish a healthier lifestyle.⁴⁷

As it is the case for Greece, increases in children adiposity have been also demonstrated in many regions worldwide, during the past decades.^{7,12,13,16,43}  Surprisingly, this is already true for both developed²² and developing countries.^58,65 Howbeit the obscure situation, there is considerable research to manifest stabilization in the prevalence of obesity in certain parts of the global^14,41  including Greece.⁵⁰ Many explanations have been put forward to analyze the background of this progression, e.g., changes in dietary and physical activity habits, a more supportive family and community environment, mainly due to intense initiatives/interventions have been taken to adverse this unhealthy condition during the recent years.⁴² The present study reported somehow similar obesity rates with studies published at the beginning of this decade^48,51,52,62; however, it is arbitrary to claim that childhood obesity in Greece is levelling off. Likewise, it seems unfound to make any inference in relation to socio-economic recession and whether the latter has provoked greater obesity expansion. More research needs to be done to facilitate claims like that.

There are some limitations that should be taken into account when interpreting the findings of this study. A first limitation is that data collection included one single measurement of each child; a longitudinal design would provide valuable information. Furthermore, additional measurements or other personal details that would be critical to determine physical condition, family or social background of the subjects, though useful, did not comply with the objectives of this study. Finally, the overweight/obesity rates found in this study can be generalized only to urbanized populations that likely share similar lifestyles.

Despite its limitations, this study provides an insight into overweight/obesity prevalence in an age group less investigated, so far. The findings revealed an overweight/obesity problem that is evident even before children enter primary school and unfortunately persists or occasionally increases during the first years in school. Since obesity is directly associated with metabolic abnormalities and major health issues,^11,48 national and local authorities ought to embrace policies and interventions, also, targeting at very young children. Examining the obesity prevalence is only the first, but not the only step in the battle against childhood obesity. Carefully designed policy interventions are needed in order to improve eating and physical activity habits in young children.

CONFLICTS OF INTEREST

The authors declare that they have no conflicts of interest.

1. Matayka K. Managing obesity in children. Obes Pract. 2004; 4(2): 2-6.

2. Veugelers PJ, Fitzgerald AL. Prevalence of and risk factors for childhood overweight and obesity. CMAJ. 2005; 173(6): 607-613. doi: 10.1503/cmaj.050445

3. Flegal KM, Kruszon-Moran D, Carroll MD, Fryar CD, Ogden CL. Trends in obesity among adults in the United States, 2005 to 2014. JAMA. 2016; 315(21); 2284-2291. doi: 10.1001/jama.2016.6458

4. Nikooyeh B, Abdollahi Z, Salehi F, et al. Prevalence of obesity and overweight and its associated factors in urban adults from West Azerbaijan, Iran: The National Food and Nutritional Surveillance Program (NFNSP). Nutr Food Scien Res. 2016; 3(2): 21-26. doi: 10.18869/acadpub.nfsr.3.2.21

5. Wu Y. Overweight and obesity in China. BMJ (Clin Res ed). 2006; 333(7564): 362-363. doi: 10.1136/bmj.333.7564.362

6. van Jaarsveld, CH, Gulliford MC. Childhood obesity trends from primary care electronic health records in England between 1994 and 2013: Population-based cohort study. Arch Dis Child.2015. 100(3): 214-219. doi: 10.1136/archdischild-2014-307151

7. Rajput N, Tuohy P, Mishra S, Smith A, Taylor, B. Overweight and obesity in 4-5-year-old children in New Zealand: Results from the first 4 years (2009-2012) of the B4School Check programme. J Paediatr Child Health. 2015; 51(3): 334-343. doi: 10.1111/jpc.12716

8. Ogden CL, Flegal KM, Carroll MD, Johnson CL. Prevalence and trends in overweight among U.S. children and adolescents, 1999-2000. JAMA. 2002; 288(14): 1728-1732. doi: 10.1001/jama.288.14.1728

9. Silveira JAC, Colugnati FAB, Cocetti M, Taddei JA. Secular trends and factors associated with overweight among Brazilian preschool children: PNSN-1989, PNDS-1996, and 2006/07. J Pediatr (Rio J). 2014; 90(2): 258-266. doi: 10.1016/j.jpedp.2013.09.002

10. Zong XN, Li H. Secular trends in prevalence and risk factors of obesity in infants and preschool children in 9 Chinese cities, 1986-2006. PLoS One. 2012; 7(10): e46942. doi: 10.1371/journal.pone.0046942

11. Chu NF. Prevalence and trends of obesity among school children in Taiwan-the Taipei Children Heart Study. Int J Obes Relat Metab Disord.2001; 25(2): 170-176. Web site. http://search.proquest.com/openview/501bfe7492e4fb99ed8a1bf11c4e424c/1?pq-origsite=gscholar&cbl=38864. Accessed November 24, 2016.

12. Júlíusson PB, Roelants M, Eide GE, Hauspie R, Waaler PE, Bjerknes R. Overweight and obesity in Norwegian children: Secular trends in weight-for-height and skinfolds. Acta Paediatr. 2007; 96(9): 1333-1337. doi: 10.1111/j.1651-2227.2007.00421.x

13. Parrino C, Rossetti P, Baratta R, et al. Secular trends in the prevalence of overweight and obesity in Sicilian schoolchildren aged 11-13 years during the last decade. PLoS One. 2012; 7(4): e34551. doi: 10.1371/journal.pone.0034551

14. Cattaneo A, Monasta L, Stamatakis E, et al. Overweight and obesity in infants and pre-school children in the European Union: A review of existing data. Obes Rev. 2010; 11(5): 389-398. doi: 10.1111/j.1467-789X.2009.00639.x

15. Drewnowski A, Specter SE. Poverty and obesity: The role of energy density and energy costs. Am J Clin Nutr. 2004; 79(1): 6-16. Web site. http://ajcn.nutrition.org/content/79/1/6.short. Accessed November 24, 2016.

16. Pařízková J, Sedlak P, Dvořáková H, Lisá L, Bláha P. Secular trends of adiposity and motor abilities in preschool children. J Obes Wt Loss Ther. 2012; 2(153): 2. doi: 10.4172/2165-7904.1000153

17. Meirhaeghe A, Helbecque N, Cottel D, Amouyel P. Beta 2-adrenoceptor gene polymorphism, body weight, and physical activity. Lancet. 1999; 353(9156): 896. Web site. http://search.proquest.com/openview/94a3f0481a74d10128ffecc8c809852e/1?pq-origsite=gscholar&cbl=40246. Accessed November 24, 2016.

18. Church TS, Thomas DM, Tudor-Locke C, et al. Trends over 5 decades in U.S. occupation-related physical activity and their associations with obesity. PLoS One. 2011; 6(5): e19657. doi: 10.1371/journal.pone.0019657

19. Manios Y, Kourlaba G, Kondaki K, Grammatikaki E, Anastasiadou A, Roma-Giannikou E. Obesity and television watching in preschoolers in Greece: The GENESIS study. Obesity. 2009; 17(11): 2047-2053. doi: 10.1038/oby.2009.50

20. Lagiou A, Parava, M. Correlates of childhood obesity in Athens, Greece. Public Health Nutr. 2008; 11(09): 940-945. doi: 10.1017/S1368980008002462

21. Classen T, Hokayem C. Childhood influences on youth obesity. Econ Hum Biol. 2005; 3(2): 165-187. doi: 10.1016/j.ehb.2005.05.008

22. Wang Y, Lobstein T. Worldwide trends in childhood overweight and obesity. Int J Pediatr Obes. 2006; 1(1): 11-25. Web site. http://www.tandfonline.com/doi/abs/10.1080/17477160600586747. Accessed November 24, 2016.

23. Manios Y, Costarelli V, Kolotourou M, Kondakis K, Tzavara C, Moschonis G. Prevalence of obesity in preschool Greek children, in relation to parental characteristics and region of residence. BMC Public Health. 2007; 7(1): 1. doi: 10.1186/1471-2458-7-178

24. Whitaker RC. Predicting preschooler obesity at birth: The role of maternal obesity in early pregnancy. Pediatrics. 2004; 114(1): 29-36. Web site. http://pediatrics.aappublications.org/content/114/1/e29.short. Accesseed November 24, 2016.

25. Stunkard AJ, Faith MS, Allison KC. Depression and obesity. Biol Psychiatry. 2003; 54(3): 330-337. doi: 10.1016/s0006-3223(03)00608-5

26. Power C, Lake JK, Cole TJ. Measurement and long-term health risks of child and adolescent fatness. Int J Obes Relat Metab Disord. 1997; 21(7): 507-526. doi: 10.1038/sj.ijo.0800454

27. Nassis GP, Papantakou K, Skenderi K, et al. Aerobic exercise training improves insulin sensitivity without changes in body weight, body fat, adiponectin and inflammatory markers in overweight and obese girls. Metab Clin Exp. 2005; 54(11): 1472-1479. doi: 10.1016/j.metabol.2005.05.013

28. Krekoukia M, Nassis GP, Psarra G, Skenderi K, Chrousos GP, Sidossis LS. Elevated total and central adiposity and low physical activity are associated with insulin resistance in children. Metab Clin Exp. 2007; 56(2): 206-213. doi: 10.1016/j.metabol.2006.09.014

29. Singla P, Bardoloi A, Parkash AA. Metabolic effects of obesity: A review. World J Diabetes. 2010; 1(3): 76-88. doi: 10.4239/wjd.v1.i3.76

30. Williams J, Wake M, Hesketh K, Maher E, Waters E. Health-related quality of life of overweight and obese children. JAMA. 2005; 293(1): 70-76. doi: 10.1001/jama.293.1.70

31. Sanderson K, Patton GC, McKercher C, Dwyer T, Venn AJ. Overweight and obesity in childhood and risk of mental disorder: A 20-year cohort study. Aust N Z J Psychiatry. 2011; 45(5): 384-392. Web site. http://www.tandfonline.com/doi/abs/10.3109/00048674.2011.570309. Accessed November 24, 2016.

32. Freedman DS, Sherry B. The validity of BMI as an indicator of body fatness and risk among children. Pediatrics. 2009; 124(1): S23-S34. Web site. http://pediatrics.aappublications.org/content/124/Supplement_1/S23.short. Acceesed November 24, 2016.

33. Singh AS, Mulder C, Twisk JW, van Mechelen W, Chinapaw MJ. Tracking of childhood overweight into adulthood: A systematic review of the literature. Obes Rev. 2008; 9(5): 474-488. doi: 10.1111/j.1467-789X.2008.00475.x

34. Baird J, Fisher D, Lucas P, et al. Being big or growing fast: Systematic review of size and growth in infancy and later obesity. BMJ. 2005; 331(7522): 929-935. doi: 10.1136/bmj.38586.411273.E0

35. Whitaker RC, Wright JA, Pepe MS, Seidel KD, Dietz WH. Predicting obesity in young adulthood from childhood and parental obesity. N Eng J Med. 1997; 337(13): 869-873. doi: 10.1056/NEJM199709253371301

36. James WPT. The epidemiology of obesity: The size of the problem. J Intern Med. 2008; 263(4): 336-352. doi: 10.1111/j.1365-2796.2008.01922.x

37. Beaglehole R, Bonita R, Horton R, et al. Priority actions for the non-communicable disease crisis. Lancet. 2011; 377(9775): 1438-1447. doi: 10.1016/S0140-6736(11)60393-0

38. Roditis ML, Parlapani ES, Tzotzas T, Hassapidou M, Krassas GE. Epidemiology and predisposing factors of obesity in Greece: From the Second World War until today. J Pediatr Endocrinol Metab. 2009; 22(5): 389-405. doi: 10.1515/JPEM.2009.22.5.389

39. Brambilla P, Vezzoni M, Lucchini R, et al. Is the prevalence of overweight reducing at age 5-6 years? Ten years data collection in ASL Milano 2. Ital J Pediatr.2012; 38(1): 24. doi: 10.1186/1824-7288-38-24

40. de Wilde JA, Verkerk PH, Middelkoop BJC. Declining and stabilising trends in prevalence of overweight and obesity in Dutch, Turkish, Moroccan and South Asian children 3-16 years of age between 1999 and 2011 in the Netherlands. Arch Dis Child. 2014; 201399(1): 46-51. doi: 10.1136/archdischild-2013-304222

41. Olds T, Maher C, Zumin S, et al. Evidence that the prevalence of childhood overweight is plateauing: Data from nine countries. Int J Pediatr Obes. 2011; 6(5-6): 342-360. Web site. http://www.tandfonline.com/doi/abs/10.3109/17477166.2011.605895. Accessed November 24, 2016.

42. Olds TS, Tomkinson GR, Ferrar KE, Maher CA. Trends in the prevalence of childhood overweight and obesity in Australia between 1985 and 2008. Int J Obes. 2010; 34(1): 57-66. doi: 10.1038/ijo.2009.211

43. Skinner AC, Skelton JA. Prevalence and trends in obesity and severe obesity among children in the United States, 1999-2012. JAMA Pediatr. 2014; 168(6): 561-566. doi: 10.1001/jamapediatrics.2014.21

44. Brinkman HJ, de Pee Saskia, Sanogo I, Subran L, Bloem MW. High food prices and the global financial crisis have reduced access to nutritious food and worsened nutritional status and health. J Nutr. 2010; 140(1): 153S-161S. doi: 10.3945/​jn.109.110767

45. Hassapidou M, Daskalou E, Tsofliou F, et al. Prevalence of overweight and obesity in preschool children in Thessaloniki, Greece. Hormones (Athens). 2015. doi: 10.14310/horm.2002.1601

46. Kambas A, Venetsanou F, Avloniti A, et al. Pedometer determined physical activity and obesity prevalence of Greek children aged 4-6 years. Ann Hum Biol. 2015; 42(3): 231-236. doi: 10.3109/03014460.2014.943286

47. Kyriazis I, Rekleiti M, Saridi M, et al. Prevalence of obesity in children aged 6-12 years in Greece: Nutritional behaviour and physical activity. Arch Med Sci. 2012; 8(5): 859-864. doi: 10.5114/aoms.2012.31296

48. Kollias A, Skliros E, Stergiou GS, Leotsakos N, Saridi M, Garifallos D. Obesity and associated cardiovascular risk factors among schoolchildren in Greece: A cross-sectional study and review of the literature. J Ped Endocrin Metab. 2011; 24(11-12): 929-938. doi: 10.1515/JPEM.2011.309

49. Kollias AK, Skliros EA, Leotsakos N, Gikas A, Garifallos D. Childhood obesity in relation to parental weight status in Greece. Hippokratia. 2009; 13(4): 253. Web site. http://hippokratia.gr/images/PDF/13-4/906.pdf. Accessed November 24, 2016.

50. Tambalis KD, Panagiotakos DB, Kavouras SA, et al. Eleven-year prevalence trends of obesity in Greek children: First evidence that prevalence of obesity is leveling off. Obesity. 2010; 18(1): 161-166. doi: 10.1038/oby.2009.188

51. Farajian P, Panagiotakos DB, Risvas G, et al. Socio-economic and demographic determinants of childhood obesity prevalence in Greece: The GRECO (Greek Childhood Obesity) study. Public Health Nutr. 2012; 16(2): 240-247. doi: 10.1017/S1368980012002625

52. Farajian P, Risvas G, Karasouli K, et al. Very high childhood obesity prevalence and low adherence rates to the Mediterranean diet in Greek children: The GRECO study. Atherosclerosis. 2011; 217(2): 525-530. doi: 10.1016/j.atherosclerosis.2011.04.003

53. Dietz WH. Critical periods in childhood for the development of obesity. Am J Clin Nutr. 1994; 59(5): 955-959. Web site. http://ajcn.nutrition.org/content/59/5/955.short. Accessed November 24, 2016.

54. Cummingham SA, Kramer MR, Nrayan KMV. Incidence of childhood obesity in the United States. N Engl J Med. 2014; 370(5): 403-411. doi: 10.1056/NEJMoa1309753

55. Skouteris H, Hartley-Clark L, McCabe M, et al. Preventing excessive gestational weight gain: A systematic review of interventions. Obes Rev. 2010; 11(11): 757-768. doi: 10.1111/j.1467-789X.2010.00806.x

56. Cole TJ, Bellizzi MC, Flegal KM, Dietz WH. Establishing a standard definition for child overweight and obesity worldwide: International survey. BMJ. 2000; 320(7244): 1240-1243. doi: 10.1136/bmj.320.7244.1240

57. Cole TJ, Flegal KM, Nicholls D, Jackson AA. Body mass index cut offs to define thinness in children and adolescents: International survey. BMJ. 2007; 335(7612): 194. doi: 10.1136/bmj.39238.399444.55

58. de Onis M, Blössner M, Borghi E. Global prevalence and trends of overweight and obesity among preschool children.  Am J Clin Nutr. 2010; 92(5): 1257-1264. doi: 10.3945/ajcn.2010.29786

59. Krassas GE, Tzotzas T, Tsametis C, Konstantinidis T. Prevalence and trends in overweight and obesity among children and adolescents in Thessaloniki, Greece.  JPEM. 2000; 14 Suppl 5: 1319-1326. Web site. http://europepmc.org/abstract/med/11964029. Accessed November 24, 2016.

60. Papadimitriou A, Kounadi D, Konstantinidou M, Xepapadaki P, Nicolaidou P. Prevalence of obesity in elementary schoolchildren living in Northeast Attica, Greece. Obesity. 2006; 14(7): 1113-1117. doi: 10.1038/oby.2006.127

61. Georgiadis G, Nassis GP. Prevalence of overweight and obesity in a national representative sample of Greek children and adolescents. Eur J Clin Nutr. 2007; 61(9): 1072-1074. doi: 10.1038/sj.ejcn.1602619

62. Makedou KG, Moschous E, Kourtis AA. Prevalence of childhood obesity in schools of Northern Greece. AUMJ. 2011; 38(1): 17-19. Web site. https://ejournals.lib.auth.gr/aumj/article/view/4685. Accessed November 24, 2016.

63. Xiao Y, Qiao Y, Pan L, et al. Trends in the prevalence of overweight and obesity among Chinese preschool children from 2006 to 2014. PLoS One.2015; 10(8): e0134466. doi: 10.1371/journal.pone.0134466

64. Sedlak P, Pařízková J, Daniš R, Dvořáková H, Vignerová J. Secular changes of adiposity and motor development in Czech preschool children: Lifestyle changes in fifty-five year retrospective study. Bio Med Res Int. 2015: 823841. doi: 10.1155/2015/823841

65. Ng M, Fleming T, Robinson M, et al. Global, regional, and national prevalence of overweight and obesity in children and adults during 1980-2013: A systematic analysis for the Global Burden of Disease Study 2013. Lancet. 2014; 384(9945): 766-781. doi: 10.1016/S0140-6736(14)60460-8