Adekunle Sanyaolu, PhD,1 Chuku Okorie, MBBS, MPH,2 Xiaohua Qi, MD, PhD,3 Jennifer Locke, MD,3 and Saif Rehman, MD3
Adekunle Sanyaolu
1Federal Ministry of Health, Abuja, Nigeria
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Chuku Okorie
2Essex County College, Newark, NJ, USA
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Xiaohua Qi
3Saint James School of Medicine, Anguilla, British West Indies
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Jennifer Locke
3Saint James School of Medicine, Anguilla, British West Indies
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Saif Rehman
3Saint James School of Medicine, Anguilla, British West Indies
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Disclaimer
1Federal Ministry of Health, Abuja, Nigeria
2Essex County College, Newark, NJ, USA
3Saint James School of Medicine, Anguilla, British West Indies
Adekunle Sanyaolu, Federal Ministry of Health, Federal Capital Territory, Abuja, Nigeria. Email: moc.liamtoh@elnukaynas
Received 2019 Feb 12; Revised 2019 Oct 12; Accepted 2019 Nov 6.
Copyright © The Author[s] 2019
This article is distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 License [//www.creativecommons.org/licenses/by-nc/4.0/] which permits non-commercial use, reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access pages [//us.sagepub.com/en-us/nam/open-access-at-sage].
Abstract
Childhood and adolescent obesity have reached epidemic levels in the United States. Currently, about 17% of US children are presenting with obesity. Obesity can affect all aspects of the children including their psychological as well as cardiovascular health; also, their overall physical health is affected. The association between obesity and other conditions makes it a public health concern for children and adolescents. Due to the increase in the prevalence of obesity among children, a variety of research studies have been conducted to discover what associations and risk factors increase the probability that a child will present with obesity. While a complete picture of all the risk factors associated with obesity remains elusive, the combination of diet, exercise, physiological factors, and psychological factors is important in the control and prevention of childhood obesity; thus, all researchers agree that prevention is the key strategy for controlling the current problem. Primary prevention methods are aimed at educating the child and family, as well as encouraging appropriate diet and exercise from a young age through adulthood, while secondary prevention is targeted at lessening the effect of childhood obesity to prevent the child from continuing the unhealthy habits and obesity into adulthood. A combination of both primary and secondary prevention is necessary to achieve the best results. This review article highlights the health implications including physiological and psychological factors comorbidities, as well as the epidemiology, risk factors, prevention, and control of childhood and adolescent obesity in the United States.
Keywords: obesity, childhood, adolescents, United States, body mass index, BMI
Introduction
Childhood and adolescent obesity have reached epidemic levels in the United States, affecting the lives of millions of people. In the past 3 decades, the prevalence of childhood obesity has more than doubled in children and tripled in adolescents. The latest data from the National Health and Nutrition Examination Survey show that the prevalence of obesity among US children and adolescents was 18.5% in 2015-2016. Overall, the prevalence of obesity among adolescents [12-19 years; 20.6%] and school-aged children [6-11 years; 18.4%] was higher than among preschool-aged children [2-5 years; 13.9%]. School-aged boys [20.4%] had a higher prevalence of obesity than preschool-aged boys [14.3%]. Adolescent girls [20.9%] had a higher prevalence of obesity than preschool-aged girls [13.5%; Figure 1]. Moreover, the rates of obesity have been steadily rising from 1999-2000 through 2015-2016 [Figure 2]. According to Ahmad et al, 80% of adolescents aged 10 to 14 years, 25% of children younger than the age of 5 years, and 50% of children aged 6 to 9 years with obesity are at risk of remaining adults with obesity.
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Figure 1.
Prevalence of obesity among children and adolescents aged 2 to 19 years, by sex and age: the United States, 2015-2016.
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Figure 2.
Trends in obesity prevalence among children and adolescents aged 2 to 19 years: the United States, 1999-2000 through 2015-2016.
Obesity can affect all aspects of children and adolescents including but not limited to their psychological health and cardiovascular health and also their overall physical health. The association between obesity and morbid outcomes makes it a public health concern for children and adolescents. Obesity has an enormous impact on both physical and psychological health. Consequently, it is associated with several comorbidity conditions such as hypertension, hyperlipidemia, diabetes, sleep apnea, poor self-esteem, and even serious forms of depression. In addition, children with obesity who were followed-up to adulthood were much more likely to suffer from cardiovascular and digestive diseases. The increase in body fat also exposes the children to increase in the risk of numerous forms of cancers, such as breast, colon, esophageal, kidney, and pancreatic cancers.
Due to its public health significance, the increasing trend in childhood obesity needs to be closely monitored. However, these trends have proved to be challenging to quantify and compare. While there are many factors and areas to consider when discussing obesity in children and adolescents, there are a few trends that are evident in recent studies. For example, the prevalence of obesity varies among ethnic groups, age, sex, education levels, and socioeconomic status. A report published by the National Center for Health Statistics using data from the National Health and Nutrition Examination Survey provides the most recent national estimates from 2015 to 2016 on obesity prevalence by sex, age, race, and overall estimates from 1999-2000 through 2015-2016. Prevalence of obesity among non-Hispanic black [22.0%] and Hispanic [25.8%] children and adolescents aged 2 to 19 years was higher than among both non-Hispanic white [14.1%] and non-Hispanic Asian [11.0%] children and adolescents. There were no significant differences in the prevalence of obesity between non-Hispanic white and non-Hispanic Asian children and adolescents or between non-Hispanic black and Hispanic children and adolescents. The pattern among girls was similar to the pattern in all children and adolescents. The prevalence of obesity was 25.1% in non-Hispanic black, 23.6% in Hispanic, 13.5% in non-Hispanic white, and 10.1% in non-Hispanic Asian girls. The pattern among boys was similar to the pattern in all children and adolescents except that Hispanic boys [28.0%] had a higher prevalence of obesity than non-Hispanic black boys [19.0%; Figure 3]. This review article is aimed at studying the health implications including physical and psychological factors and comorbidities, as well as the epidemiology, risk factors, prevention, and control of childhood and adolescent obesity in the United States.
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Figure 3.
Prevalence of obesity among children and adolescents aged 2 to 19 years, by sex and race and Hispanic origin: the United States, 2015-2016.
Methodology
We performed a literature search using online electronic databases [PubMed, MedlinePlus, Mendeley, Google Scholar, Research Gate, Global Health, and Scopus] using the keywords “childhood,” “adolescents,” “obesity,” “BMI,” and “overweight.” Articles were retrieved and selected based on relevance to the research question.
Ethical Approval and Informed Consent
Ethics approval and informed consent were not required for this narrative review.
Definition of Childhood Obesity
Defining obesity requires a suitable measurement of body fat and an appropriate cutoff range. Body mass index [BMI] was calculated as weight in kilograms divided by height in meters squared, rounded to 1 decimal place. Obesity in children and adolescents was defined as a BMI of greater than or equal to the age- and sex-specific 95th percentile and overweight with a BMI between the 85th and 95th percentiles of the 2000 Centers for Disease Control and Prevention [CDC] growth charts.
However, the use of the BMI percentile according to the age/sex of the CDC growth charts for very high BMIs can result in estimates that differ substantially from those that are observed,, and this constrains the maximum BMI that is attainable at given sex and age., These limitations have resulted in the classification of severe obesity as a BMI ≥120% of the 95th percentile rather than a percentile greater than the 95th percentile., A BMI of 120% of the 95th percentile corresponds to a BMI of ~35 among 16 to 18 year olds.
Physiology of Energy Regulation and Obesity
Obesity is a chronic multifactorial disease, characterized by an excessive accumulation of adipose tissue, commonly as a result of excessive food intake and/or low energy expenditure. Obesity can be triggered by genetic, psychological, lifestyle, nutritional, environmental, and hormonal factors.
Obesity is found in individuals that are susceptible genetically and involves the biological defense of an elevated body fat mass, the mechanism of which could be explained in part by interactions between brain reward and homeostatic circuits, inflammatory signaling, accumulation of lipid metabolites, or other mechanisms that impair hypothalamic neurons.
Normal energy regulation physiology is under tight neurohormonal control. The neurohormonal control is performed in the central nervous system through neuroendocrine connections, in which circulating peripheral hormones, such as leptin and insulin, provide signals to specialized neurons of the hypothalamus reflecting body fat stores and induces appropriate responses to maintain the stability of these stores. The hypothalamic region is where the center of the regulation of hunger and satiety is located. Some of them target the activity of endogenous peptides, such as ghrelin, pancreatic polypeptide, peptide YY, and neuropeptide Y, as well as their receptors.
The physiology of energy regulation may result in obesity in susceptible people when it goes awry from genetic and environmental modulators. There is strong evidence of the majority of obesity cases that are associated with central resistance to both leptin and insulin actions., The environmental modulators equally play critical roles in obesity. Changes in the circadian clock are associated with temporal alterations in feeding behavior and increased weight gain. Stress interferes with cognitive processes such as executive function and self-regulation. Second, stress can affect behavior by inducing overeating and consumption of foods that are high in calories, fat, or sugar; by decreasing physical activity; and by shortening sleep. Third, stress triggers physiological changes in the hypothalamic-pituitary-adrenal axis, reward processing in the brain, and possibly the gut microbiome. Finally, stress can stimulate the production of biochemical hormones and peptides such as leptin, ghrelin, and neuropeptide Y.
The lateral hypothalamus [LH] plays a fundamental role in regulating feeding and reward-related behaviors; however, the contributions of neuronal subpopulations in the LH are yet to be identified thoroughly. The LH has also been associated with other aspects of body weight regulation, such as physical activity and thermogenesis. The LH contains a heterogeneous assembly of neuronal cell populations, in which γ-aminobutyric acid [GABA] neurons predominate. LH GABA neurons are known to mediate multiple behaviors important for body weight regulation, thus altering energy expenditure.
Etiology and Risk Factors
Excess body fat is a major health concern in childhood and adolescent populations. The dramatic increase in childhood obesity foreshadows the serious health consequences of their adult life. As obesity begins from childhood and spans through adult life, it becomes increasingly more difficult to treat successfully. Being able to identify the risk factors and potential causes of childhood obesity is one of the best strategies for preventing the epidemic.
According to the Morbidity and Mortality Weekly Report released in 2011, there is an acceptance that there is no single cause of childhood obesity and that energy imbalance is just a part of the numerous factors. Many children have a discrepancy between what is taken in and what is expended. For example, children with obesity consume approximately 1000 calories more than what is necessary for their body to function healthily and to be able to participate in regular physical activities. Over 10 years, there will be an excess of 57 pounds of unnecessary weight. With excessive caloric intake, as well as sedentary lifestyles, childhood obesity will continue to rise if no changes are implemented. Adding daily physical activity, better sleep patterns, as well as dietary changes can help decrease the number of excess calories and help with obesity-related problems in the future.
Also, during childhood, excess fat accumulates when the increase in caloric intake exceeds the total energy expenditure. Furthermore, children living in the United States today compared with children living in the 1900s are participating in more than 6 hours per day activities on social media. This includes but is not limited to traditional television, video gaming, and blogging/Facebook activities. An additional economic rationalization for the increase in childhood obesity is technology. In other words, Americans can now eat more in less time.
In a study, Cutler et al found that an increase in consumption of food tends to be related to technology innovation in food production and transportation. Technology has thus made it increasingly possible for firms to mass prepare food and ship to consumers for ready consumption, thereby taking advantage of scale economies in food preparation. The result of this change has been a significant reduction in the time costs for food production. These lower time costs have led to increased food consumption and, ultimately, increased weights. Eliminating the time cost of food preparation disproportionately increases consumption for hyperbolic discounters because time delay is a particularly important mechanism for discouraging those individuals from consuming. Society today prefers immediate satisfaction with regard to food and convenience over the long-term goals of living a long, healthy life. The availability of high-caloric, less-expensive food coupled with the extensive advertisement and easy accessibility of these foods has contributed immensely to the rising trend of obesity. For example, there have been reductions in the price of McDonalds and Coca-Cola [5.44% and 34.89%, respectively] between 1990 and 2007, while there was about a 17% increase in the price of fruits and vegetables between 1997 and 2003.
Likewise, only 16% of children walk or bike to school today as compared with 42% in the late 1960s. However, the distance, convenience, weather, scanty sidewalks, and anxiety about crimes against children could all contribute to this difference. Furthermore, with elementary, middle, and high school combined, only 13.8% of these schools provide adequate daily physical education classes for at least 4 hours a week.
Some other potential risk factors have been reported through research studies that involve issues that affect the child in utero and childhood. Table 1 represents potential risk factors and confounders of childhood obesity.
Table 1.
Potential Risk Factors of Childhood Obesity.
Family characteristicsParent’s BMI during pregnancyNumber of siblings of the child at 18 monthsThe ethnicity of the childAge of the mother at deliveryChildhood lifestyleTime spent watching TVTime in the car per day [weekdays/weekend]Duration of night sleepDietary patternInfant feedingBreast feeding/formula feedingAge of introduction to solid foodsIntrauterine and perinatal factorsBirthweightSexMaternal parityMaternal smoking during pregnancy [28-32 weeks]Season of birth [winter, summer, fall, spring]Number of fetusesOtherMaternal social class [SES]Maternal educationEnergy intake of the child
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Abbreviations: BMI, body mass index; SES, socioeconomic status.
Catalano et al argues that maternal BMI before conception, independent of maternal glucose status or birth weight, is a strong predictor of childhood obesity. Infants at the highest quarter for weight at 8 and 18 months are more likely to become children with obesity at age 7, than children in the lower quarters. Certain behaviors have been linked to childhood obesity and overweight; these are a lack of physical activity and unhealthy eating patterns [eating more food away from home, drinking more sugar-sweetened drinks, and snacking more frequently], resulting in excess energy intake., In addition, when one parent presents with obesity, there is an increased potential for the child to become obese over the years. Naturally, the risk is higher for the children when both parents present with obesity. Furthermore, a study that followed children over time observed that children who got less sleep