Breast-Feeding and Childhood Obesity

Breast-Feeding and Childhood Obesity. von Kries R, Koletzko B, Sauerwald T, von Mutius E, Barnert D, Grunert V, von Voss H. Breast feeding and obesity: Cross sectional study. BMJ 1999;319:147–50. Summary: Von Kries et al. studied the impact of breast-feeding during infancy on the risk of being overweight or obese in 9357 German children aged 5 to 6 years. They performed a cross-sectional survey using data collected from obligatory health examinations before school entry. Previously determined age-and sex-specific distribution of body mass index (BMI) among German children was taken as reference (overweight, BMI >90th percentile; obese, BMI >97th percentile). Of the 9357 children studied, information on breast-feeding and its duration was available on 9206. Of this number, 4022 children had never been breast-fed, and 5184 had been breast-fed. The prevalence of obesity in those who had never been breast-fed was 4.5%, compared with 2.8% in the breast-fed children. A clear dose–response effect was identified for the duration of breast-feeding on the prevalence of obesity: the prevalence was 3.8% for 2 months, 1.7% for 6 to 12 months, and 0.8% for more than 12 months. After adjusting for confounding variables such as the level of parental education and maternal smoking during pregnancy, breast-feeding remained a significant protective factor against the development of obesity (odds ratio [OR] 0.75; 95% confidence interval [CI] 0.57–0.98) and being overweight (OR 0.79, CI 0.68–0.93). Comments: It is estimated that as many as 250 million people worldwide may be obese, and the prevalence of obesity is increasing in most parts of the world (Acta Paediatr 1999;(Suppl)428:46–50). Recent data suggest that approximately 22% of American children and adolescents may be overweight and that 11% are obese (Pediatrics 1999;103:E85). The cause of obesity is multifactorial, but environmental influences probably play a greater role. Genetic and hormonal factors are rarely the cause of childhood obesity (Am Fam Phys 1999;59:861–8). Although other investigators have examined the subject, von Kries et al. conducted one of the largest epidemiologic studies assessing the impact of breast-feeding on the risk of obesity in childhood. In 1979, a Finnish study of 238 full-term infants showed that breast-feeding for at least 6 months protected them from obesity at 1 year of age (Acta Paediatr Scand 1979;68:245–50). Kramer et al., in a prospective study of 462 term infants, showed that the duration of breast-feeding was a significant determinant of BMI at 12 months of age (J Pediatr 1985;106:10–4). Investigators in a case–control study of 639 cases and 533 controls also concluded that breast-feeding protected against development of obesity at age 12 to 18 years (J Pediatr 1981;98:883–7). None of these earlier studies demonstrated any dose–response effect of the duration of breast-feeding on the prevalence of obesity. Other workers have found no association between breast-feeding and development of obesity (Obes Res 1997;6:538–41), and some have even associated breast-feeding with increased risk of becoming overweight (J Pediatr 1990;116:805–9;Endocr Reg 1991;25:53–7). The results of some of these studies are difficult to interpret in the context of the findings of Von Kries et al., because the different authors used different criteria for defining overweight or obesity. The World Health Organisation has now recommended the use of BMI-for-age percentiles as uniform criteria for the assessment of childhood obesity (Acta Paediatr 1999;(Suppl)428: 46–50). Childhood obesity is on the increase worldwide, and it is considered to be a silent epidemic in America (Curr Opin Pediatr 1998;10:422–7). The cause of this increase is poorly understood and has been postulated to be related to imbalances in energy input and expenditure, sedentary life styles, high-fat foods, and numerous other environmental factors including overfeeding, overprotection by parents, and the number of hours spent in watching television. Childhood obesity is well recognised to be an antecedent to adult obesity (N Engl J Med 1976;295:6–9;BMJ 1981;283:13–17;Int J Obes Relat Metab Disord 1997;21:912–21). Approximately one third of obese preschool children and approximately one half of obese school-aged children may grow up to be obese adults (Prev Med 1993;22:167–77). Obesity-related illnesses such as type 2 diabetes in children has increased 10-fold during the past decade in the United States (Am J Clin Nutr 1998;68:944S–9S). Childhood obesity has been shown to be associated with increased risk of adult cardiovascular disease (Pediatrics 1999;103:1175–82), and a 57-year follow-up of a cohort of 1165 boys and 1234 girls (age range, 2–14 years) also demonstrated a definite association between childhood obesity and death caused by cardiovascular disease in adults (Am J Clin Nutr 1998;67:1111–8). Earlier in 1992, Must et al. (N Engl J Med 1992;327:1350–5) showed that overweight in adolescence is a powerful predictor of mortality, cardiovascular disease, colorectal cancer, gout, and arthritis, irrespective of adult weight, after 55 years of follow-up. Recently, much interest has been shown in the role of early nutrition and the health of the individual in adulthood (Proc Nutr Soc 1999;58:75–8). Evidence for “programming by nutrition” is well established in animals, in whom brief pre-or postnatal nutritional manipulations may program adult size, metabolism, blood lipids, diabetes, blood pressure, obesity, atherosclerosis, learning, behaviour, and life span (J Nutr 1998;128(2 Suppl)401S–6S). Adverse socioeconomic circumstances in childhood have been shown to be associated with increased risk of death from coronary heart disease and respiratory disease in adulthood (BMJ 1998;316:1631–5) and ischaemic heart disease in middle-aged men (BMJ 1990;301:1121–3). Nutritional programming is therefore an attractive hypothesis that could explain the impact of breast-feeding on the prevalence of obesity in children and adults. Obesity can no longer be viewed as merely a cosmetic or social problem but must be acknowledged as a serious condition responsible for premature deaths and significant morbidity in millions worldwide. Management of obesity and related illnesses may consume a significant proportion of limited healthcare resources. In 1997, the direct cost of obesity in Canada was estimated to be over $1.8 billion corresponding to 2.4% of the total health expenditure for all diseases in Canada in 1997 (Can Med Assoc J 1999;160:483–8). The treatment of obesity, which includes dietary and physical activity management, behaviour modification, and family involvement (Am Fam Phys 1999;59:861–8), is costly and usually difficult to institute. If, as suggested by von Kries et al., breast-feeding decreases the prevalence of obesity in childhood, the promotion of breast-feeding could be an important and economical public health tool in the fight against the rising incidence of obesity.