US childhood obesity – Nearly 1 in 5 kids are obese

Nearly 1 in 5 U.S. kids are obese, according to the latest national data.

The news is disappointing, given that programs across the country have for years been trying to reduce childhood obesity, one expert said.

“We really were expecting and hoping to see the trends decrease,” said Dr. Tannaz Moin, a UCLA obesity researcher.

Obesity – which means not merely overweight, but seriously overweight – is one of the nation’s leading public health problems.

Adult obesity also has been trending upward, but childhood obesity is especially worrisome because it can put kids on track for problems like diabetes and heart disease, she said.

The Centers for Disease Control and Prevention findings come from a gold-standard health survey that measures participants’ height and weight. The latest data come from surveys done in 2017 and 2018, when more than 2,800 U.S. children participated.

It found 19.3% of kids ages 2 to 19 were obese. That’s up slightly from the 18.5% in the 2015-2016 national survey. The increase isn’t considered statistically significant, meaning there’s a mathematical chance the rates didn’t truly rise.

But it follows an upward trend since 2005-2006, when 15.4% of U.S. kids were obese.

The percentage of kids who are severely obese remains at about 6%, where it’s been for several years, the CDC found.

A range of factors contribute to childhood obesity, including eating a lot of processed foods and sugary beverages, and a lack of physical exercise.

The current coronavirus crisis – with school closings and stay-at-home orders—can’t be helping, Moin said.

“Kids for the most part are at home, and not at school with recess, and getting even less (physical) activity,” she said.

“We may see worse trends in the coming years, especially if this pandemic continues the way it is.”

The CDC quietly released the findings last month in an infographic in the back of one of its publications.

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BMI for Children and Teens

Body mass index (BMI) is a measure used to determine childhood overweight and obesity. Overweight is defined as a BMI at or above the 85^th percentile and below the 95^th percentile for children and teens of the same age and sex.

Obesity is defined as a BMI at or above the 95th percentile for children and teens of the same age and sex.

BMI is calculated by dividing a person’s weight in kilograms by the square of height in meters. For children and teens, BMI is age- and sex-specific and is often referred to as BMI-for-age.

A child’s weight status is determined using an age- and sex-specific percentile for BMI rather than the BMI categories used for adults. This is because children’s body composition varies as they age and varies between boys and girls.

Therefore, BMI levels among children and teens need to be expressed relative to other children of the same age and sex.

For example, a 10-year-old boy of average height (56 inches) who weighs 102 pounds would have a BMI of 22.9 kg/m². This would place the boy in the 95^th percentile for BMI, and he would be considered as obese. This means that the child’s BMI is greater than the BMI of 95% of 10-year-old boys in the reference population.

The CDC Growth Charts are the most commonly used indicator to measure the size and growth patterns of children and teens in the United States. BMI-for-age weight status categories and the corresponding percentiles were based on expert committee recommendations and are shown in the following table.

Weight Status Category	Percentile Range
Underweight	Less than the 5th percentile
Normal or Healthy Weight	5th percentile to less than the 85th percentile
Overweight	85th to less than the 95th percentile
Obese	95th percentile or greater

BMI does not measure body fat directly, but research has shown that BMI is correlated with more direct measures of body fat, such as skinfold thickness measurements, bioelectrical impedance, densitometry (underwater weighing), dual energy x-ray absorptiometry (DXA) and other methods(a,b,c).

BMI can be considered an alternative to direct measures of body fat. A trained healthcare provider should perform appropriate health assessments in order to evaluate an individual’s health status and risks.

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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.1

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).1

Moreover, the rates of obesity have been steadily rising from 1999-2000 through 2015-2016 (Figure 2).1

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.2

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.3 The association between obesity and morbid outcomes makes it a public health concern for children and adolescents.4

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.5

In addition, children with obesity who were followed-up to adulthood were much more likely to suffer from cardiovascular and digestive diseases.3

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.6

Due to its public health significance, the increasing trend in childhood obesity needs to be closely monitored.7 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 2015-2016.1

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).1

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.

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.15

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.16

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,17 peptide YY, and neuropeptide Y,18 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.19,20 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.21 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.17

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.22 The LH has also been associated with other aspects of body weight regulation, such as physical activity and thermogenesis.23

The LH contains a heterogeneous assembly of neuronal cell populations, in which γ-aminobutyric acid (GABA) neurons predominate.23 LH GABA neurons are known to mediate multiple behaviors important for body weight regulation, thus altering energy expenditure.23

Psychological Consequences of Obesity

Several studies related to childhood and adolescent obesity have focused primarily on physiological consequences. Other studies have been conducted regarding the association between psychiatric disorders and obesity; these have resulted in conflict due to obesity being found to be an insignificant factor for psychopathology.

However, a comparative study by Britz et al found that high rates of mood, anxiety, somatoform, and eating disorders were detected among children with obesity. The study also observed that most psychiatric disorders began after the onset of obesity.

In this large population-based study, it was found that a staggering 60% of females and 35% of males reported that they have engaged in binge eating and expressed a lack of control over their diet.37

Goldfield et al conducted a study among 1400 adolescents with obesity, overweight, and normal weight in grades 7 to 12. Their BMIs, as determined by the International Obesity Task Force, were the criteria used to define each group.

Each participant completed a questionnaire on body images, eating behaviors, and moods. Adolescents with obesity reported significantly higher body dissatisfaction, social isolation, depression symptoms, anhedonia, and negative self-esteem than those of normal weight.38

There is widespread stigmatization of people with obesity that causes harm rather than the intention to motivate people to lose weight. Stigma contributes to behaviors such as binge eating, social isolation, avoidance of health care services, decreased physical activity, and increased weight gain, which worsens obesity and creates additional barriers to healthy behavior change.39

Weight-based bullying in youth is considered a common, serious problem in many countries.40 In a study conducted by O’Brien et al, to test whether the association between weight stigma experiences and disordered eating behaviors, that is, emotional eating, uncontrolled eating, and loss-of-control eating, are mediated by weight bias internalization and psychological distress among 634 undergraduate university students, and results of statistical analyses showed that weight stigma was significantly associated with all measures of disordered eating, and with weight bias internalization and psychological distress.41

Asthma and Obesity

There is mounting evidence that childhood obesity is a risk factor for the development of asthma.42 A research study was conducted by Belamarich et al to investigate 1322 children aged 4 to 9 years with asthma. Obesity, as defined by the CDC, is the BMI, with weight and height being greater than the 95th percentile.

This was the criteria used to identify the 249 children with obesity, while the BMI between the 5th and 95th percentile identified the children who were not obese. After a baseline assessment was done, the 9-month study found that the children with obesity had a higher number of days of wheezing over 2 weeks (4.0 vs 3.4) and as well had more unscheduled emergency hospital visits (39% vs 31%).42

Obesity directly correlates with the severity of asthma, as well as poor response to corticosteroids.43 In fact, children with obesity who also have a history of asthma are more challenging to control and linked to worse quality of life.44 A prospective trial found that weight loss in patients with obesity and a history of asthma can significantly aid them to control the asthma attacks.43

Chronic Inflammation and Childhood Obesity

Lumeng and Saltiel reported that obesity in children affects multiple organ systems and predisposes them to diseases. The effect of obesity on the tissue can manifest in the development of insulin-resistant type 2 diabetes, the risk of cancer, and pulmonary diseases.45

The inflammatory response to obesity triggers pathogens, systematic increases in circulatory inflammatory cytokines, and acute-phase reactants (eg, C-reactive proteins), which inflames the tissues.

This is often caused by the activation of tissue leukocytes. Chronic inflammation in children with obesity can induce meta-inflammation that is unique when compared with other inflammatory paradigms (eg, infection, autoimmune diseases).45

Researchers have reported that children with obesity are at risk of lifelong meta-inflammation. In these children, the inflammatory markers are elevated as early as in the third year of life.45,46 This has been linked to heart disease later in life.19 The long-term consequences of such findings can cause cumulative vascular damage that correlates with the increased weight status.47

The short-term and long-term effects of obesity on the health of children is a significant concern because of the negative psychological and health consequences.46 The potential negative psychological outcomes are depressive symptoms, poor body image, low self-esteem, a risk for eating disorders, and behavior and learning problems.

Additional negative health consequences include insulin resistance, type 2 diabetes, asthma, hypertension, high total, and low-density lipoprotein cholesterol and triglyceride levels in the blood, low high-density lipoprotein cholesterol levels in the blood, sleep apnea, early puberty, orthopedic problems, and nonalcoholic steatohepatitis46,47 (Figure 4). Children with obesity are more likely to become adults with obesity, thus increasing their risk for several diseases before they even reach their teen years.48

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References

(a) Barlow SE and the Expert Committee. Expert committee recommendations regarding the prevention, assessment, and treatment of child and adolescent overweight and obesity: summary report. Pediatrics 2007;120 Supplement December 2007:S164—S192.

(b) Cote AT, Harris KC, Panagiotopoulos C, et al. Childhood obesity and cardiovascular dysfunction. J Am Coll Cardiol 2013; 62 (15):1309–1319.

(c) Whitlock EP, Williams SB, Gold R, Smith PR, Shipman SA. Screening and interventions for childhood overweight: a summary of evidence for the US Preventive Services Task Force. Pediatrics. 2010;116(1):e125—144external icon.

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