Childhood Obesity: Critical Periods for the Development and Growth of Obesity - Essay Example

All these years focus of obesity research has been on environmental factors that promote inactive lifestyle and excess energy intakes, and studies to locate other factors influencing childhood obesity have been few. In addition to fetal life, the period of adiposity rebound, and adolescence overweight onset at early infancy, influenced by parent's diet choice, also constitute a critical period for the development of adulthood obesity. Outline for research I Introduction to obesity prevalence A. Existing tenets of obesity prevalence 1. Lack of physical activity, sedentary behavior, parental obesity 2. Eating habits, environmental factors, genetic and metabolic conditions B. Critical periods for development of obesity 1. Adiposity rebound 2. Changes in BMI during infancy 3. Body composition assessment II Studies on obesity onset from infancy A. Maternal malnutrition and poverty B. Parent's food choice and eating behavior and its influence on male and female children C. Social and environmental impact on eating habits III Effect of life style changes in preventing obesity A. Selection of foods and importance of calorie check B. Regular physical exercise. Childhood Obesity: Critical Periods for the Development and Growth of Obesity Introduction Obesity is a major medical problem generally developed from our own bad habits, and it has reached epidemic proportion in the United States, as around one-third of the U.S. population is obese based on Body Mass Index (BMI) criteria. There is steady increase of obesity epidemic not only among adults, but children in the United States are also overweight and a history of childhood overweight continuing into adulthood is linked to more severe complications in later life. Considering the alarming spread of obesity epidemic world over, numerous studies are being sponsored by government, educational, and scientific institutions to identify factors affecting onset of obesity in children from birth. Studies points out that overweight children are also significantly more likely to become overweight or obese as adults, which prompted researchers to identify 'critical periods' in which physiological alterations increase the later prevalence of obesity. Several studies suggest an "association between increased rates of weight gain during the first 4 to 24 months of life and risk of overweight during later childhood or early adulthood" (Dennison et al). All these years focus of obesity research has been on environmental factors that promote inactive life style and excess energy intakes and studies to locate variety of factors influencing childhood obesity, such as malnutrition, dietary habits of parents, food choice, as well as critical pathways of childhood overweight continuing into adulthood obesity has not been thoroughly explored. Prevalence of Childhood Obesity In the United States "more than 65% of adults are overweight or obese", with nearly 31 percent adults meeting criteria for obesity, and "approximately 16% of childhood and teens ages 6 through 19 are overweight." (A Report of the NIH Obesity Research Task Force, 2004) Statistical evidence show that, since 1970, prevalence of obesity has more than doubled for preschool children (aged 2-5) and adolescents (aged 12-19) and more than tripled for children aged 6-11 years. (Overview of the IOM's Childhood Obesity Prevention Study). Research findings suggest that lack of physical activity, sedentary behavior, parental obesity, socioeconomic status, eating habits, and environmental factors, as well as genetic and metabolic conditions are coincident with the increased incidence of overweight. In addition, socioeconomic development and global changes in diet and behavioral patterns, namely intake of diet rich in fat, salt, sugar, and calorie, depending more on transportation than walking for attending school, office, and visiting friends and relatives, and drop in sports and games have promoted overweight in younger generations. Overweight children are vulnerable to developing many health conditions and diseases, such as: Insulin resistance; Type 2 diabetes; Hypertension, early onset of puberty, infertility, orthopedic problems, eating disorder, sleep interruption, and cardiovascular disease. As children are not generally in the recognized productivity range there is no lost wages, yet the cost of preventive, diagnostic, and treatment services raises more concern about the health of younger generation in future. However, NIH strategic plan includes many initiatives focused on childhood obesity such as paediatric primary care setting and multi-pronged school-based prevention trial, because focus on the needs of children is critically important. Any effort to prevent obesity, with particular emphasis to childhood obesity, will be successful only when the fundamental causes for the tendency to add more weight or failure to expend calories consumed by an individual from infancy to old age are identified. Critical periods for development of obesity It is now recognized that the identification of 'critical periods', the developmental stages in which physiological alterations increase the later prevalence of obesity, for the growth of obesity may help identifying the body system that accumulate fat and focusing preventive efforts. Many observations suggest that there are three critical periods for the development of obesity, such as "the prenatal period, the period of adiposity rebound, and adolescence" and onset of obesity during these periods appears to increase the risk of persistent obesity and its complications (Dietz, 1994). It is found that infants exposed to maternal under-nutrition in utero have an increased risk of obesity. Data analysis on infant obesity prevalence suggests that body mass index (BMI) increases in the first year of life and subsequently decreases, it again increases around 6 years of age and this second period is known as the period of adiposity rebound. Adolescence is the third period for development of obesity. Dietz (1994) point out that the 'relative risks of the complications' or persistence of obesity that originate at each of the three critical periods remain unclear and 'age-specific therapeutic success rates have not been established.' It establishes that 'critical periods', the developmental stages in which physiological alterations increase the later prevalence of obesity, play crucial role in physiological alterations. As such, body composition assessment of young children, particularly during 'adiposity rebound' will be helpful in identifying the reasons behind prevalence of obesity during adolescence and later life. Body composition assessment for identifying obesity Obesity is scientifically identified on the basis of an individual's Body Mass Index, and it refers to body weight that is at least 30 percent over the ideal weight for a specified height in accordance with BMI. In general sense it can be termed as excess of body weight compared to normal accepted standard of accumulated fat. Body composition assessment of young children, particularly during 'adiposity rebound' with its unique pattern of body size development, is viewed as the most effective approach in identifying the repercussions of future risk of obesity in children. Though there are a variety of methods to measure body composition, these methods vary in their sophistication, accuracy, feasibility, cost, and availability and some procedures are unsuitable for young children. It is found that 'skinfolds (SFs) and bioelectrical impedance analysis (BIA)', compared with other methods, offer good feasibility and reasonable accuracy in body composition measure. An examination of interrelationships of body composition measures derived from anthropometry of young children in 3-8 years old by Eisenmann, Heelan, and Welk (2004) to identify whether an earlier age at adiposity rebound affects an individual to the development of obesity found that "an earlier age at adiposity rebound is related to subsequent risk of overweight". The research findings confirm that age range of adiposity rebound, represented by change in BMI and SFs, is a decisive period for development of obesity. Studies on onset of obesity Literature on obesity studies reveal that onset of obesity begins from the womb, as under nutrition in the womb affects fetus' metabolism. Reduced availability of nutrients may train the fetus' metabolism to conserve rather than use calories, which prompt the body to add more calories during infancy as well as adult life, when more nutrients are available. In view of these findings United National Food and Agricultural Organization propose that "reducing malnutrition in pregnant women shall be able to protect their children from developing obesity "(The Endocrine Society Handbook. 9). In a scientific review of evidence to confirm the "association between infant size or growth during the first two years of life and subsequent obesity" revealed that infants born with highest BMI or who grew rapidly during infancy are at greater risk for future rapid growth and becoming obese. (Baird). Stettler, et al (2003), in a cohort study of African Americans, most vulnerable groups for obesity, found that "a pattern of rapid weight gain during early infancy is associated with obesity not only in childhood but also in young adulthood." A cross sectional survey to determine whether fast weight gain between birth and 6 months has any link with childhood and later adolescent obesity relationship, as well as ethnicity associated variations was conducted by Barbara A. Dennison and team in New York setting. The study sample covered Hispanic, black, and white population as well as limited information about breast feeding history; where representation of Hispanic population and breast feeding history are two new domains untouched by researchers of childhood obesity. Dennison et al (2006) found that rapid infant weight gain was associated with increased risk of being overweight at 4 years of age, Hispanic children were twice being overweight than non-Hispanic children, which is consistent with other studies, and any protective effect of breast-feeding on the risk of childhood overweight was absent. Though overfeeding is considered as one of the most likely causes, the causes of rapid infant weight gain are unknown. Hence, Dennison et al. (2006) suggests that 'there is a real need for more research to understand the parent-child mechanism, genetic and ethnic determinants, and environmental factors that present increased risk for rapid infant weight gain and the development of childhood overweight and adult obesity.' Parental influence on children's eating behavior Children's eating behavior, development of food preferences, and physical activity are developed from family settings, and parental tastes, feeding strategies adopted, and food made available to children play an important role in childhood overweight. Of these, feeding strategies play an important role as restriction of junk foods and total amount of food as well as pressurizing children to eat healthy foods and eat more in general may pose adverse effects than the expected positive results. Some parents may offer restricted foods, like sweetmeat as bribe, for pressuring a child to eat healthy foods, which may lead to increased desire for restricted foods when children get free access to them. Similarly, parental restrictions of focusing children's attention on food portion size rather than hunger and satiety may also result in poorer eating regulation. Most of the earlier research on parent's influence on children's eating habit formations have focused on mother's eating behaviors and its effect on young girls, but studies on father's feeding practice and its influence on children's' eating behavior are few. Johannsen et al (2006) investigated the effects of mothers' and fathers' eating behaviors, child feeding practices, and BMI on percentage body fat and BMI in their children. They, assumed that mothers' dietary restraint or inhibition, control in child feeding, and BMI would positively relate to daughters' weight status. It was also assumed that mothers' dietary behavior and physical nature do not influence the sons' weight status, and fathers' role in family eating behavior and children's weight outcomes was considered insignificant. After the study they found that children's weight was related to mothers' BMI and mothers exert a strong influence over their children's eating behavior, whereas, fathers play a role in imposing child feeding practices and are more concerned about their daughters' future health. But, girls with more controlling fathers had higher percentage fat. The study throws light on the reality that mothers' BMI plays a decisive role rather than their disinhibited eating behavior in making their offspring overweight. At the same time the findings become inconclusive, because the research subjects with higher BMI were also having disinhibited eating behavior and their children exhibited both characteristics of higher BMI and uninhibited dietary habit. Another important point to be noted is that the children selected for the study were too young to decide their taste and dietary preferences, rather than obeying the parental preference, which will definitely influence research conclusions. However, studies by Christakis et al found that obesity may spread in social networks depending on the nature of social ties, and "pairs of friends and siblings of the same sex appeared to have more influence on the weight gain of each other than did pairs of friends and siblings of the opposite sex" (Christakis and Fowler). This study establishes that mothers' dietary habit could influence their daughters' than that of sons'. Hence, lifestyle changes are inevitable for controlling obesity. Taste development and food choice of children Obesity and excess weight gain in children and young adults can be associated with consumption of snacks containing fat and sodium, sugar rich caloric beverages, and large portion size fast foods. Taste preferences for fat and sugar are powerful sources of 'neurobiological reward' as energy-dense foods provide more sensory enjoyment and pleasure than energy-dilute foods, which have high water content. The taste preference for fat and sugar are either inherent in humans or acquired very early in life as studies of the food preferences of 3 to 4 years old children showed that "preferences were motivated by familiarity and the energy density of the foods" (Drewnowski and Specter). Familiarity to taste and food choice of children are naturally developed by mothers or whoever initiates an infant to first feed other than breast milk, and the food choice preferred for an infant is dependent on their own preferences. Only after an infant is grown up enough to decide his or her taste and preferences they will become demanding for energy-dense foods such as chocolate chip cookies, sweetened breakfast cereals, or pizza. When mothers or attendants refrain from low-energy-dense food items in their daily intake there will be a normal tendency among infants to avoid such foods, and commercial advertisements will also influence their food choice. As such, "whether induced by innate taste preferences, early exposure, or other environmental factors, long-term dietary exposure to sugar and fat may have permanent metabolic consequences on the organism" (Drewnowski and Specter, 2004). Mothers and attendants of an infant should not be solely blamed for inculcating taste for high energy-dense foods, because their limited economic resources may be the driving force for choosing 'an energy-dense, highly palatable diet that provides maximum calories per the least volume and the least cost', rather than following wrong dietary habits for themselves and their children. Effect of Life style changes in preventing obesity Foods contain vitamins, minerals, and hundreds of naturally occurring substances that fortify our body against chronic health conditions and, hence, the nutrients required should come primarily from food that we consume, rather than from fortified foods. Choosing meals and snacks that are high in nutrients, but low to moderate in energy content, and that is beneficial for normal growth and development of children is important in keeping calories under control. Eating nutrient-dense foods, which provide substantial amounts of vitamins and minerals and relatively few calories and avoiding food items containing added sugar, saturated fats, and sodium preservative, will help reduce calorie intake. Hence, consumption of whole grains, breakfast cereals rich in vitamin E, fruits, vegetables, and low-fat and fat-free milk and milk products will provide adequate amount of nutrients needed for healthy growth of children. It is well established that regular physical activity checks obesity and can reduce insulin resistance, risk of type 2 diabetes, cardiovascular risk in adults, and improve glucose intolerance. Compared to adults, much less research has examined the influence of physical activity on obesity-related metabolic risk factors in children and adolescents. Since physical activity has the power to reduce the risk of obesity related maladies and offers a natural and drug-free intervention approach, greater emphasis should be given for physical activity and its measurement. Conclusion In addition to fetal life, the period of adiposity rebound, and adolescence overweight onset at early infancy also constitute a critical period for the development of adulthood obesity. Though maternal malnutrition, dietary preference, and food habits play crucial role in childhood obesity, which can be checked through lifestyle modifications, strategy to control the tendency to add weight during infancy, particularly during critical period of development pauses more challenge before researchers and healthcare providers. Identifying the reasonable cause of overweight among children at young age, educating youth about adverse effect of overweight as early as possible, and introducing new initiatives for bringing life style changes as well as upgrading surveillance system will be necessary to prevent incidence of overweight in the U.S. population Works cited Christakis, Nicholas A., and Fowler, James H. The Spread of Obesity in a Large Social Network over 32 years. New England Journal of Medicine. Vol. 357, No. 4. 16 Jul. 2008. . Dennison, Barbara A et al. Obesity: Rapid Infant Weight Gain Predicts Childhood Overweight. Nature.com. 2006. 16 Jul. 2008. . A Report of the NIH Obesity Research Task Force. NIH Publication. 2004. 16 Jul. 2008. . Overview of the IOM's Childhood Obesity Prevention Study. Institute of Medicine of the National Academies. 2004. 16 Jul. 2008. . Dietz, William H. (1994). Critical periods in childhood for the development of obesity. Am J Clin Nutr. Vol. 59 (955-9). . Baird, Janis et al. Being big or Growing Fast: Systematic Review of Size and Growth in Infancy and Later Obesity. bmj.com. 22 Oct. 2005. 16Jul. 2008. . Stettler, Nicolas et al. Original Research Communication. The American Journal of Chemical Nutrition. 2003. 16 Jul. 2008. . Johannsen, Darcy L et al. Obesity: Influence of Parent's Eating Behaviours and Child Feeding Practices on Children's Weight Status. The Obesity Society. 2006. 16 Jul. 2008. . Drewnowski, Adam., and Specter, SE. Poverty and Obesity: The Role of Energy Density and Energy Costs. The American Journal of Chemical Nutrition. 2004. 16 Jul. 2008. . Read More