C H A P T E R 1 In developing countries determinants of childhood obesity include high socioeco-‐ nomic status, residence in metropolitan cities, female gender, unawareness and false beliefs about nutrition, marketing by transnational food companies, increasing academic stress, and poor facilities for physical activity4. In the past, in the devel-‐ oped countries obesity was seen particularly in individuals with high socioeconom-‐ ic status, in the wealthy population, because of excess food intake. To date, obesity is particularly seen in the lower income groups. In an attempt to account for this fact are more fast food intake, less exercise, more playing computer games and watching television. Causes for obesity are health styles and also genetic backgrounds are mentioned. Some gene defects have been described which could be related to a predisposition to obesity. Particularly FTO (Fat mass and obesity-‐associated protein also known as alpha-‐ketoglutarate-‐dependent dioxygenase FTO), MC4R (Melanocortin receptor 4), and TMEM18 (Transmembrane protein 18) loci are described in the develop-‐ ment of obesity. MC4R mutations are associated with inherited human obesity. They were found in heterozygotes, suggesting an autosomal dominant inheritance pattern. However, based on other research and observations, these mutations seem to have an incomplete penetrance and some degree of codominance. It has a preva-‐ lence of 1-‐2.5% in people with BMI’s > 30, making it the most common known ge-‐ netic defect predisposing people to obesity21. Although some genes have been found for pediatric obesity, there is still a lot more to be learned, and the future involves looking at rare variants, gene-‐by-‐gene and gene-‐by-‐environment interac-‐ tions, and epigenetic factors22. Metabolic syndrome The concern about overweight in childhood is based on the observation that it leads to obesity in adulthood and thereby to a risk of developing the metabolic syndrome, not only with regard to adults but also with regard to children. The metabolic syn-‐ drome has become one of the major health problems of our times. Associated obesi-‐ ty, dyslipidemia, atherosclerosis, hypertension, and type 2 diabetes add up to shorten life spans, whereas hyperandrogenism with polycystic ovarian syndrome affect the quality of life and fertility of increasing numbers of women23. In 2007, the International Diabetes Federation (IDF) proposed a definition of pedi-‐ atric metabolic syndrome using age-‐specific diagnostic criteria: (1) children aged 6–10 years who are obese (defined as waist circumference ≥90th percentile) and have other relevant risk factors such as family history of cardiometabolic disease and (2) children aged 10–16 years who are obese and meet the adult metabolic syndrome criteria for triglycerides (TGs), HDL-‐cholesterol (HDL-‐C), blood pressure (BP), and glucose concentrations24. 14
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