Obesity was first recognised as a disease by Hippocrates, who recommended dieting, physical exercise, and sun exposure as preventative measures. Unfortunately, this is easier said than done. According to data from the global burden of disease study in 2013, childhood obesity levels worldwide rose by 47.1% from 1980 to 2013.  This occurred at the greatest rate not in developed nations, where images of rotund children in front of television screens have been commonplace for generations, but in the developing world, where it is becoming an under recognised health crisis. 
Graph showing comparison of US childhood (>18y) obesity with 12 middle and low-income countries 
Insufficient nutrition is still an issue for many countries worldwide, and is where international aid has typically been directed.  In many countries however, there is an increasing dual burden as both ends of the malnutrition spectrum are becoming overrepresented, such as in Kyrgyzstan, where 15.8% of children are underweight and 28.2% overweight.  Ironically, underweight children have a far greater likelihood (than those with normal BMI) of being overweight in adulthood. This is evident as early as foetal life. Low birth weight has been associated with increased risk of central adiposity and metabolic syndrome, whereas high birth weight is associated with a higher average BMI.  Low birth weight is due to poor nutrition during pregnancy, and the obesity association is borne out by studies showing that low-energy intake, very low-protein intake or inadequate micronutrient intake in pregnancy was associated with greater risk of obesity among offspring. 
ECHO is the Commission on Ending Childhood Obesity, established in 2014 by the World Health Organisation (WHO) director general Dr Margaret Chan. According to the recently published ECHO report, 41 million children under the age of 5 are overweight worldwide.  If current trends continue, by 2025 that number will be 70 million. Many of these children live in low and middle-income countries. Clearly, the blame for this does not lie with the children themselves, but rather with the environment in which they are being brought up. The report has termed the ubiquity of low-nutrient, high-calorie foods ‘obesogenic’, and declining levels of child physical activity exacerbates this effect. In one study, only 22.4% of Saudi Arabian pre-school aged children achieved the recommended 10,000 steps. 
Junk foods are both cheap and readily available, and there is little education in many countries about the dangers of obesity and junk food. In many cultures, excess weight is seen as a sign of affluence, and is an indicator of the good health of a child. This is particularly true of children being raised by parents who were brought up in environments of scarcity. Crawford et al. found that Hispanic parents perceive children whose weight for height is above the 85th percentile to be healthier than children with lower percentiles.  A change in these attitudes is essential to reverse the global obesity pandemic.
Childhood obesity has dire consequences for global health, both immediately, and in years to come. Childhood obesity is associated with metabolic syndrome, which is characterised by multiple factors including central obesity (around the visceral organs), abnormal lipid levels in the blood, hypertension, and insulin resistance.  In one study of Chinese schoolchildren, 35.2% of obese adolescents fit the diagnostic criteria of metabolic syndrome.  The insulin resistance found in this syndrome is a precursor to type II diabetes mellitus. Obese children are at greatly increased risk of atherosclerosis, polycystic ovarian syndrome, and often experience early puberty. Critically, childhood obesity is a strong predictor of adult obesity, which has a multitude of health and economic consequences, both for the individual and society as a whole. 
Clearly this issue must be addressed, but obesity is a multifactorial problem, and there is no panacea. A concerted effort by governments and health organisations worldwide will be necessary to improve the situation. To that end, WHO has created a list of recommendations and objectives, the full list of which can be found in the report.  There are six key tenets of the approach – the most ambitious of which are: universally improved antenatal guidance, reduced availability of unhealthy food, increased physical activity, provision of weight management resources, and better education on healthy choices. These are sensible, effective measures, and if implemented correctly will greatly benefit future generations. However, overturning cultural paradigms surrounding food will take time, and before this happens, our unhealthy food obsession may well have condemned millions of children to a life of ill health, both in the world’s poorest nations, and right here at home.
Anna-Lucia Koerling is a second-year medical student at Emmanuel College, Cambridge. She has a particular interest in the role of behavioural psychology on public health.
 Ng, Marie 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, The Lancet, 384(9945); 766 – 781
 Report of the Comission on Ending Childhood Obesity (2016), WHO, http://apps.who.int/iris/bitstream/10665/204176/1/9789241510066_eng.pdf
 World Food Program (UN-WFP) website – http://www.wfp.org/our-work –
 Tzioumis E, Adair LS. Childhood dual burden of under- and over-nutrition in low- and middle-income countries: a critical review. Food and nutrition Bulletin. 2014; 35(2):230-243. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4313560/
 Yang Z, Huffman S. Nutrition in pregnancy and early childhood and associations with obesity in developing countries. Maternal & Child Nutrition. 2013; 9(S1): 105-119
 Christian P.& Stewart C.P. Maternal micronutrient deficiency, foetal development, and the risk of chronic disease. The Journal of Nutrition. 2010; 140: 437–445.
 Al-Hazzaa HM , Al-Rasheedi AA. Adiposity and physical activity levels among preschool children in Jeddah, Saudi Arabia. Saudi Medical Journal. 2007; 28: 766–773
 Crawford, P.B., et al. Perceptions of child weight and health in Hispanic parents: implications for the California FitWIC Childhood Obesity Prevention Project. The 129th Annual Meeting of APHA, Atlanta, GA. October 21–25 2001. Abstract No. 32301.
 Gupta N, Goel K, Shah P, Misra A. Childhood Obesity in Developing Countries: Epidemiology, Determinants, and Prevention. Endocrine Reviews. 2012;33(1): 48-70 – http://press.endocrine.org/doi/full/10.1210/er.2010-0028#_i58
 Li Y , Yang X , Zhai F , Piao J , Zhao W , Zhang J , Ma G. Childhood obesity and its health consequence in China.Obes Rev. 2008; 9(Suppl 1):82–86
 Biro F, Wien M. Childhood Obesity and Adult Morbidities. Am J Clin Nutr. 2010; 91(5): 1499S-1505S
Lobstein T. et al. Child and adolescent obesity: part of a bigger picture. The Lancet. 2015; 385(9986): 2510-2520
Junk Food Image – http://www.fitnessbin.com/wp-content/uploads/2015/08/unhealthy-food-1396551439-b68002a4.jpg