Childhood obesity

The first problems to occur in obese children are usually emotional or psychological.[10] Obese children often experience bullying by their peers.[11][12] Some are harassed or discriminated against by their own family.[12] Stereotypes abound and may lead to low self-esteem and depression.[13]

Childhood obesity however can also lead to life-threatening conditions including diabetes, high blood pressure, heart disease, sleep problems, cancer, and other disorders.[14][15] Some of the other disorders would include liver disease, early puberty or menarche, eating disorders such as anorexia and bulimia, skin infections, and asthma and other respiratory problems.[16]

The early physical effects of obesity in adolescence include, almost all of the child's organs being affected, gallstones, hepatitis, sleep apnoea and increased intracranial pressure.[17] Overweight children are also more likely to grow up to be overweight adults.[15] Obesity during adolescence has been found to increase mortality rates during adulthood.[18]

A 2008 study has found that children who are obese have carotid arteries which have prematurely aged by as much as thirty years as well as abnormal levels of cholesterol.[19]

[22]

Children who are obese are likely to be obese as adults. Thus, they are more at risk for adult health problems such as heart disease, type 2 diabetes, stroke, several types of cancer, and osteoarthritis. A large population based study showed that adolescents who were overweight or obese had a 2.2 times risk of sudden death and a 3.5 times increased risk for death from coronary heart disease or stroke in adulthood as compared to normal BMI peers.[23][6] Another study showed that those with an elevated BMI in childhood and adulthood were at an elevated risk of certain chronic medical conditions including a 5.4 times increased risk of diabetes, 2.7 times increased risk of hypertension, and 1.8 times increased risk of elevated LDL cholesterol (a cholesterol-based measure of risk of atherosclerosis) in adulthood. However, in children or adolescents with elevated BMI who reduce their BMI to normal levels, these risks are decreased to a similar level as those with normal BMI in childhood and adulthood.[24][6] One study showed that children who became obese as early as age 2 were more likely to be obese as adults.[25] According to an article in The New York Times all of these health effects are contributing to a shorter lifespan of five years for these obese children. It is the first time in two centuries that the current generation of children in America may have a shorter lifespan than their parents.[26]

Childhood obesity is often the result of an interplay between many genetic and environmental factors. Polymorphisms in various genes controlling appetite and metabolism predispose individuals to obesity when sufficient calories are present. Over 200 genes affect weight by determining activity level, food preferences, body type, and metabolism.[36] Having two copies of the allele called FTO increases the likelihood of both obesity and diabetes.[37]

As such, obesity is a major feature of a number of rare genetic conditions that often present in childhood:

• Prader–Willi syndrome with an incidence between 1 in 12,000 and 1 in 15,000 live births is characterized by hyperphagia and food preoccupations which leads to rapid weight gain in those affected.
• Bardet–Biedl syndrome
• MOMO syndrome
• Leptin receptor mutations
• Congenital leptin deficiency
• Melanocortin receptor mutations

In children with early-onset severe obesity (defined by an onset before ten years of age and body mass index over three standard deviations above normal), 7% harbor a single locus mutation.[38][39]

One study found that 80% of the offspring of two obese parents were obese in contrast to less than 10% of the offspring of two parents who were of normal weight.[1][40] The percentage of obesity that can be attributed to genetics varies from 6% to 85% depending on the population examined.[41]

In the recent decades, family practices have significantly changed, and several of these practices greatly contribute to childhood obesity:[5]

• With a decreasing number of mothers who breast-feed, more infants become obese children as they grow up and are reared on infant formula instead.[42]
• Fewer children go outside and engage in active play as technology, such as television and video games, keeps children indoors.
• Rather than walking or biking to a bus-stop or directly to school, more school-age children are driven to school by their parents, reducing physical activity.
• As family sizes decrease, the children's pester power, their ability to force adults to do what they want, increases. This ability enables them to have easier access to calorie-packed foods, such as candy and soda drinks.
• The social context around family meal-time plays a role in rates of childhood obesity

Former First Lady Michelle Obama with students in Virginia sampling healthy meals being introduced by the United States Department of Agriculture

Different communities and nations have adopted varying social practices and policies that are either beneficial or detrimental to children's physical health. These social factors include:[5]

• the quality of school lunches
• the emphasis of schools on physical activity
• access to vending machines and fast-food restaurants
• prevalence of and access to parks, bike paths, and sidewalks
• government subsidies for corn oil and sugar
• advertising of fast-food restaurants and candy
• prices of healthy and unhealthy foods
• access to fresh, healthy, and affordable food[43]

Advertising of unhealthy foods to children increases their consumption of the product[44] and positive attitudes (liking or wanting to buy) about the advertised product.[45] Children's critical reasoning (the ability to understand what an advertisement is and the aim of advertising to buy the product) is not protective against the impact of advertising, and does not appear to be fully developed during adolescence.[45] In some nations, advertising of candy, cereal, and fast-food restaurants is illegal or limited on children's television channels.[46] The media defends itself by blaming the parents for yielding to their children's demands for unhealthy foods.[5]

It is much more common for young people who come from a racial or ethnic minority, or for those who have a lower socioeconomic status, to be overweight and to engage in less healthy behaviors and sedentary activities.[47]

Maternal body mass index (BMI) is an important predictor of childhood obesity. Mothers with pre-pregnancy obesity, as defined by BMI ≥30 kg/m², are known to have children that have higher growth rates and more likely to have obesity.[53]

The effects of eating habits on childhood obesity are difficult to determine. A three-year randomized controlled study of 1,704 3rd grade children which provided two healthy meals a day in combination with an exercise program and dietary counsellings failed to show a significant reduction in percentage body fat when compared to a control group. This was partly due to the fact that even though the children believed they were eating less their actual calorie consumption did not decrease with the intervention. At the same time observed energy expenditure remained similar between the groups. This occurred even though dietary fat intake decreased from 34% to 27%.[54] A second study of 5,106 children showed similar results. Even though the children ate an improved diet there was no effect found on BMI.[55] Why these studies did not bring about the desired effect of curbing childhood obesity has been attributed to the interventions not being sufficient enough. Changes were made primarily in the school environment while it is felt that they must occur in the home, the community, and the school simultaneously to have a significant effect.[40]

A Cochrane review of a lower fat diet in children (30% or less of total energy) to prevent obesity found the existing evidence of very low to moderate quality, and firm conclusions could not be made.[56]

Calorie-rich drinks and foods are readily available to children. Consumption of sugar-laden soft drinks may contribute to childhood obesity. In a study of 548 children over a 19-month period the likelihood of obesity increased 1.6 times for every additional soft drink consumed per day.[57][58]

Calorie-dense, prepared snacks are available in many locations frequented by children. As childhood obesity has become more prevalent, snack vending machines in school settings have been reduced by law in a small number of localities. Some research suggests that the increase in availability of junk foods in schools can account for about one-fifth of the increase in average BMI among adolescents over the last decade.[59] Eating at fast food restaurants is very common among young people with 75% of 7th to 12th grade students consuming fast food in a given week.[60] The fast food industry is also at fault for the rise in childhood obesity. This industry spends about $4.2 billion on advertisements aimed at young children. McDonald's alone has thirteen websites that are viewed by 365,000 children and 294,000 teenagers each month. In addition, fast food restaurants give out toys in children's meals, which helps to entice children to buy the fast food. According to a 2010 report, 40% of children aged 2 to 11 asked their parents to take them to McDonald's at least once a week, and 15% of preschoolers asked to go every day.[61][62] To make matters worse, out of 3000 combinations created from popular items on children's menus at fast food restaurants, only 13 meet the recommended nutritional guidelines for young children.[63] Some literature has found a relationship between fast food consumption and obesity.[64] Including a study which found that fast food restaurants near schools increases the risk of obesity among the student population.[65]

Whole milk consumption verses 2% milk consumption in children of one to two years of age had no effect on weight, height, or body fat percentage. Therefore, whole milk continues to be recommended for this age group. However the trend of substituting sweetened drinks for milk has been found to lead to excess weight gain.[66]

Some jurisdictions use laws and regulations in an effort to steer children and parents towards making healthier food choices. Two examples are calorie count laws and banning soft drinks from sale at vending machines in schools.[67] In 2017 the Obesity Health Alliance called on the United Kingdom government which would be formed after that year's general election to take measures to reduce childhood obesity, for example by banning advertisements for unhealthy foods before 9:00 pm and banning sports sponsorship by manufacturers of unhealthy foods. The failure of Theresa May's then incumbent government to cut sugar, fat and salt content in foods was criticised by health groups.[68] Health experts, the health select committee and campaigners described Conservative plans over childhood obesity as, "weak" and "watered down".[69]

Secondary students in Havana, Cuba during a physical education class

Physical inactivity of children has also shown to be a serious cause, and children who fail to engage in regular physical activity are at greater risk of obesity. Researchers studied the physical activity of 133 children over a three-week period using an accelerometer to measure each child's level of physical activity. They discovered the obese children were 35% less active on school days and 65% less active on weekends compared to non-obese children.

Physical inactivity as a child could result in physical inactivity as an adult. In a fitness survey of 6,000 adults, researchers discovered that 25% of those who were considered active at ages 14 to 19 were also active adults, compared to 2% of those who were inactive at ages 14 to 19, who were now said to be active adults.[70] Staying physically inactive leaves unused energy in the body, most of which is stored as fat. Researchers studied 16 men over a 14-day period and fed them 50% more of their energy required every day through fats and carbohydrates. They discovered that carbohydrate overfeeding produced 75–85% excess energy being stored as body fat and fat overfeeding produced 90–95% storage of excess energy as body fat.[71]

Many children fail to exercise because they spend long periods of time engaging in sedentary activities such as computer usage, playing video games or watching television. Technology has a large factor on the children's activeness. Researchers provided a technology questionnaire to 4,561 children, ages 14, 16, and 18. They discovered children were 21.5% more likely to be overweight when watching 4+ hours of TV per day, 4.5% more likely to be overweight when using a computer one or more hours per day, and unaffected by potential weight gain from playing video games.[71] A randomized trial showed that reducing TV viewing and computer use can decrease age-adjusted BMI; reduced calorie intake was thought to be the greatest contributor to the BMI decrease.[72]

Technological activities are not the only household influences of childhood obesity. Low-income households can affect a child's tendency to gain weight. Over a three-week period researchers studied the relationship of socioeconomic status (SES) to body composition in 194 children, ages 11–12. They measured weight, waist girth, stretch stature, skinfolds, physical activity, TV viewing, and SES; researchers discovered clear SES inclines to upper class children compared to the lower class children.[73]

Childhood inactivity is linked to obesity in the United States with more children being overweight at younger ages. In a 2009 preschool study 89% of a preschoolers' day was found to be sedentary while the same study also found that even when outside, 56 percent of activities were still sedentary. One factor believed to contribute to the lack of activity found was little teacher motivation,[74] but when toys, such as balls were made available, the children were more likely to play.[74]

Children's food choices are also influenced by family meals. Researchers provided a household eating questionnaire to 18,177 children, ranging in ages 11–21, and discovered that four out of five parents let their children make their own food decisions. They also discovered that compared to adolescents who ate three or fewer meals per week, those who ate four to five family meals per week were 19% less likely to report poor consumption of vegetables, 22% less likely to report poor consumption of fruits, and 19% less likely to report poor consumption of dairy foods. Adolescents who ate six to seven family meals per week, compared to those who ate three or fewer family meals per week, were 38% less likely to report poor consumption of vegetables, 31% less likely to report poor consumption of fruits, and 27% less likely to report poor consumption of dairy foods.[75] The results of a survey in the UK published in 2010 imply that children raised by their grandparents are more likely to be obese as adults than those raised by their parents.[76] An American study released in 2011 found the more mothers work the more children are more likely to be overweight or obese.[77]

Various developmental factors may affect rates of obesity. Breast-feeding for example may protect against obesity in later life with the duration of breast-feeding inversely associated with the risk of being overweight later on.[78] A child's body growth pattern may influence the tendency to gain weight. Researchers measured the standard deviation (SD [weight and length]) scores in a cohort study of 848 babies. They found that infants who had an SD score above 0.67 had catch up growth (they were less likely to be overweight) compared to infants who had less than a 0.67 SD score (they were more likely to gain weight).[79] Additionally, breastfeeding for less than 6 months, compared to 6 months or more, has been shown to result in a higher growth rate and higher BMI at 18, 36, and 72 months of age.[53]

A child's weight may be influenced when he/she is only an infant. Researchers also did a cohort study on 19,397 babies, from their birth until age seven and discovered that high weight babies at four months were 1.38 times more likely to be overweight at seven years old compared to normal weight babies. High weight babies at the age of one were 1.17 times more likely to be overweight at age seven compared to normal weight babies.[80]

Cushing's syndrome (a condition in which the body contains excess amounts of cortisol) may also influence childhood obesity. Researchers analyzed two isoforms (proteins that have the same purpose as other proteins, but are programmed by different genes) in the cells of 16 adults undergoing abdominal surgery. They discovered that one type of isoform created oxo-reductase activity (the alteration of cortisone to cortisol) and this activity increased 127.5 pmol mg sup when the other type of isoform was treated with cortisol and insulin. The activity of the cortisol and insulin can possibly activate Cushing's syndrome.[81]

Hypothyroidism is a hormonal cause of obesity, but it does not significantly affect obese people who have it more than obese people who do not have it. In a comparison of 108 obese patients with hypothyroidism to 131 obese patients without hypothyroidism, researchers discovered that those with hypothyroidism had only 0.077 points more on the caloric intake scale than did those without hypothyroidism.[82]

Researchers surveyed 1,520 children, ages 9–10, with a four-year follow up and discovered a positive correlation between obesity and low self-esteem in the four-year follow up. They also discovered that decreased self-esteem led to 19% of obese children feeling sad, 48% of them feeling bored, and 21% of them feeling nervous. In comparison, 8% of normal weight children felt sad, 42% of them felt bored, and 12% of them felt nervous.[83]

Stress can influence a child's eating habits. Researchers tested the stress inventory of 28 college females and discovered that those who were binge eating had a mean of 29.65 points on the perceived stress scale, compared to the control group who had a mean of 15.19 points.[84] This evidence may demonstrate a link between eating and stress.

Feelings of depression can cause a child to overeat. Researchers provided an in-home interview to 9,374 adolescents, in grades seven through 12 and discovered that there was not a direct correlation with children eating in response to depression. Of all the obese adolescents, 8.2% had said to be depressed, compared to 8.9% of the non-obese adolescents who said they were depressed.[85] Antidepressants, however, seem to have very little influence on childhood obesity. Researchers provided a depression questionnaire to 487 overweight/obese subjects and found that 7% of those with low depression symptoms were using antidepressants and had an average BMI score of 44.3, 27% of those with moderate depression symptoms were using antidepressants and had an average BMI score of 44.7, and 31% of those with major depression symptoms were using antidepressants and had an average BMI score of 44.2.[86]

Several studies have also explored the connection between Attention-deficit Hyperactivity Disorder (ADHD) and obesity in children. A study in 2005 concluded that within a subgroup of children who were hospitalized for obesity, 57.7% had co-morbid ADHD.[87] This relationship between obesity and ADHD may seem counter-intuitive, as ADHD is typically associated with higher level of energy expenditure, which is thought of as a protective factor against obesity.[88] However, these studies determined that children exhibited more signs of predominantly inattentive-type ADHD rather than combined-type ADHD. It is possible, however, that the symptoms of hyperactivity typically present in individuals with combined-type ADHD are simply masked in obese children with ADHD due to their decreased mobility.[87] The same correlation between obesity and ADHD is also present in adult populations.[89] Existing underlying explanations for the relationship between ADHD and obesity in children include but are not limited to abnormalities in the hypo-dopaminergic pathway, ADHD creating abnormal eating behaviors which leads to obesity, or impulsivity associated with binge eating leading to ADHD in obese patients.[89][90] A systematic review of the literature on the relationship between obesity and ADHD concluded that all reviewed studies reported ADHD patients were heavier than expected.[90] However, the same systematic review also claimed that all the evidence supporting this connection was still limited and further research is still necessary to learn more about this connection.[90] Given the prevalence rates of both obesity and ADHD in children, understanding the possible relationship between the two is important for public health, particularly when exploring treatment and management options.

Direct intervention for psychological treatment of childhood obesity has become more prevalent in recent years. A meta-analysis of the psychological treatment of obesity in children and adolescents found family-based behavioral treatment (FBT) and Parent-Only Behavior treatment to be the most effective practices in treating obesity in children within a psychological framework.[91]

Exclusive breast-feeding is recommended in all newborn infants for its nutritional and other beneficial effects.[78] Parents changing the diet and lifestyle of their offspring by offering appropriate food portions, increasing physical activity, and keeping sedentary behaviors at a minimum may also decrease the obesity levels in children.[95]

If children were more mobile and less sedentary, the rate of obesity would decrease. Parents should recognize the signs and encourage their children to be more physically active. By walking or riding a bike, instead of using motorised transport or watching television, will reduce sedentary activity.[96]

As of 2023 there are several anti-obesity medications which are approved by the FDA for the treatment of obesity in adolescents. These medications are only recommended for use in conjunction with an intensive behavioral and lifestyle counselling program.[6] Orlistat is a lipase inhibitor which prevents the absorption of fats after meals. It is approved in children 12 years and older, but it's use is often limited due to adverse reactions of bowel urgency, fecal incontinence, flatulence and it may cause deficiencies in fat soluble vitamins.[6] Phentermine is an amphetamine analogue which is used as an appetite suppressant, it may be used for up to 12 weeks at a time in adolescents 16 years and older. Possible adverse reactions include headache, nausea, palpitations, elevations in blood pressure, restlessness or insomnia.[6] Phentermine is also available in combination with topiramate extended release and the combination approved for use in adolescents 12 years and older.[6] Topiramate is an anticonvulsant, but has been shown to cause weight loss. Phentermine-topiramate XR has similar possible side effects as phentermine and users should be on contraception due to the risk of teratogenic effects of the medication.[6] Liraglutide and semaglutide are glucagon-like peptide-1 receptor agonists which are approved for the treatment of obesity in adolescents 12 years and older. Liraglutide is a once daily injection and semaglutide is a once weekly injection.[6] They are thought to work by delaying gastric emptying, decreasing appetite and increasing satiety. Possible side effects of liraglutide or semaglutide include gastrointestinal distress including nausea, vomiting, diarrhea or constipation, abdominal discomfort or indigestion.[6] Liraglutide and semaglutide should not be used in those with a personal or family history of medullary type thyroid cancers as they may increase the risk of these types of tumors. And their use is further contraindicated in those with acute kidney injury, gallbladder disease or a history of pancreatitis.[6] Setmelanotide is approved for children 6 years or older with certain types of secondary obesity. It may cause skin hyperpigmentation or other dermatologic effects as well as gastrointestinal side effects, with rare instances of depression and suicidal ideation.[6]

Metformin is often used off label in children or adolescents with obesity, and has been found to cause a 1.1 decrease in the BMI.[6] A Cochrane review in 2016 concluded that medications might reduce BMI and bodyweight to a small extent in obese children and adolescents. This conclusion was based only on low quality evidence.[97]

Bariatric surgical procedures are increasingly used amongst adolescents with severe adolescent obesity to promote weight loss.[98] Laparoscopic adjustable gastric banding showed greater weight loss than lifestyle management in a small study.[99] Roux-en-Y gastric bypass and vertical sleeve gastrectomy are two surgical procedures currently used in adolescent obesity with varying sucess rates. The two types of procedures have shown a 26% weight loss from baseline at 5 years with an 86% remission rate in diabetes and 68% hypertension remission rate.[6] Of those adolescents who lost weight after bariatric surgery, 60% maintained at least a 20% weight loss at 5 year follow up and 8% had regained most of the pre-surgical weight.[6] Lack of pre-surgical weight loss is associated with an increased risk of weight gain after bariatric surgery.[6] Other risks of bariatric surgery in adolescents may include nutrient deficiencies (including vitamin B12, folate and iron), the risk of bone mass loss, and a questionable risk of alcohol use disorders later in life.[6]

The rate of overweight and obesity among Canadian children has increased dramatically in recent years. In boys, the rate increased from 11% in the 1980s to 30% in the 1990s.[103]

The rate of overweight and obesity in Brazilian children increased from 4% in the 1980s to 14% in the 1990s.[103] In 2007 the prevalence of children overweight and childhood obesity was 11.1% and 2.7% in girls, 8.2% and 1.5% in boys, respectively.[104]

The rate of obesity among children and adolescents in the United States has nearly tripled between the early 1980s and 2000. It has however not changed significantly between 2000 and 2006 with the most recent statistics showing a level just over 17 percent.[105] In 2008, the rate of overweight and obese children in the United States was 32%, and had stopped climbing.[106] In 2011, a national cohort study of infants and toddlers found that nearly one-third of US children were overweight or obese at 9 months and 2 years old.[107] In a follow-up study, infant weight status (healthy and obese) was strongly associated with preschool weight status.[108]

Since the onset of the 21st century, Australia has found that childhood obesity has followed trend with the United States. Information garnered has concluded that the increase has occurred in the lower socioeconomic areas where poor nutritional education has been blamed.