Childhood obesity is the condition of being severely overweight between the ages of 2 and 19 years. The U.S. Centers for Disease Control and Prevention (CDC) defines overweight for children as having a body mass index (BMI) between the 85th and 95th percentile. It defines obesity in children as having a BMI at or above the 95th percentile. Childhood obesity is of increasing concern as a public health problem worldwide.
According to the CDC, in 2014 about 17% of children and adolescents ages 2 to 19 were obese. This number had remained fairly stable since 2011, after years of steady increase. Rates increase as children grow older. About 9% of 2 to 5-year-olds were obese, and these rates increased to 17.5% of 6 to 11-year-olds and 20.5% of 12 to 19-year-olds.
The number of children who are overweight or obese differs significantly among various races and ethnic groups. Among Hispanics, almost 21% of children were obese, as were about 20% of non-Hispanic blacks. Among non-Hispanic whites, the obesity rate was about 15%. Obesity is common among children in low-income families, in which 14.5% of two- to four-year-olds are obese.
Global prevalence of obesity tripled between 1975 and 2016. According to the World Health Organization (WHO), in 2016, 18% of children and adolescents aged 5–19, or 340 million children worldwide, were either overweight or obese. About 123 million of these children and adolescents were actually obese. In 1975, only 4% of this age group was overweight or obese. The problem was once restricted to wealthy countries but is now rising in low and middle-income countries, especially in cities. In Africa, for example, the number of overweight children under five increased 50% between 2000 and 2016.
Most healthcare professionals calculate obesity using the body mass index (BMI). BMI is a calculation that compares a person's weight and height to arrive at a specific number.
BMI for children is calculated the same way it is for adults, but, unlike for adults, age and gender are taken into consideration. The BMIs of children between the ages of 2 and 19 are compared against growth charts based on age and gender, referred to as BMI-for-age percentiles. A child's percentile indicates how his or her weight compares to other children who are the same age and gender. For example, if a boy is in the 65th percentile for his age group, 65 of every 100 children who are his age weigh less than he does and 35 of every 100 weigh more than he does.
The BMI weight categories for children are:
In the early 2000s, many health organizations avoided applying the term “obese” to children. Children between the 85th and 95th percentile were classified as “at risk for overweight” and children above the 95th percentile were called “overweight.” No child was labeled obese, in part because of the social stigma the word carries. By 2018, however, the term “obesity” had come into common usage even for children. The CDC now defines overweight for children as having a body mass index (BMI) between the 85th and 95th percentile. It defines obesity in children as having a BMI at or above the 95th percentile.
Children who are classified in the top 15th percentile are at risk of developing weight-related health problems. One criticism of BMI, however, is that it does not take into consideration such factors as muscle mass. Certain adolescent athletes, such as wrestlers or weightlifters, may be categorized as overweight or obese when using BMI calculations, even if they are fit and in good health.
An alternative explanation of obesity is that it is a metabolic disorder caused by an excess of insulin. Pediatric endocrinologist Robert Lustig is one of many doctors who espouse this explanation, in which high insulin levels make people gain weight and simultaneously make them unable to burn their fat stores. A diet that contains a large amount of sugar and that might involve the regular consumption of sugary drinks throughout the day never lets insulin levels drop, which keeps the body in fat-storage mode. Carbohydrates, in particular sugar, cause insulin levels to rise; fats do not. By this explanation, obesity is not the result of overeating but instead the result of persistently high insulin levels, which come from eating a high-carbohydrate diet. Blaming obesity on overeating effectively blames the victim for choosing bad habits, which is unreasonable; no one wants to be obese, and obese children certainly have not chosen to overeat.
Factors implicated in childhood obesity include:
The CDC indicates obesity is also related to changes in behavior that include reduced physical activity and different eating habits. Dietary patterns have changed considerably since the 1970s. The overall environment has become obesogenic, that is, generating obesity. Food products are available everywhere and are easily acquired from sources including convenience stores and vending machines, some of which are installed in schools. Fast food restaurants provide quick, high-calorie meals that taste good and appeal to children. Sugar is added to nearly all processed foods. Food advertising bombards people with encouragements to eat. Children may prefer highly processed foods over whole, natural meats, fruits, and vegetables, making it difficult for parents to feed them healthy meals that they will eat. Grocery stores stock foods that are designed specifically to appeal to children and may place them at levels that children can see; for example, sugary breakfast cereals in boxes with colorful cartoon characters may be placed on the lower levels of the grocery shelves, where children can spot them and ask for them. The outdoor environment has been built up in a way that makes physical activity difficult or dangerous. Fewer children walk or bike to school, and outdoor play time has decreased as children spend leisure hours indoors.
Maternal obesity is associated with childhood obesity. The children of a woman who is obese during pregnancy are likely to be obese themselves and to have a high risk of later developing coronary heart disease, stroke, type 2 diabetes, and asthma. Maternal obesity can also lead to poorer cognitive performance and increased risk of neurodevelopmental disorders, including cerebral palsy. Research published in The Lancet in 2016 found that maternal obesity was a significant factor in health problems during childhood and later adult life, and warned of serious public health implications related to current obesity levels that may spread into the future, as women with obesity produce children.
Some researchers place much of the blame on increased amounts of refined starches and sugar in the diet, especially of fructose. Though sugar consumption started increasing in the late 19th century, it skyrocketed in the late 20th century after the USDA issued its policy favoring a low-fat diet. People reduced their consumption of fats, especially saturated fats, eating less red meat, full-fat dairy, bacon, eggs, and other foods that had been more common in the 1950s and 1960s. They replaced the proportion of their diets that had been composed of fats with carbohydrates and sugars. Manufacturers added sugar to processed foods to make them palatable. At the same time, people were encouraged to eat multiple times a day, and parents began giving their children snacks between most meals. Even parents who thought they were giving their children healthy foods were in fact feeding them a high-sugar diet because juice contains as much sugar as soda, and skim milk contains more sugar than whole milk.
Activity levels have dropped significantly, with fewer children getting around on foot or by bicycle, and many children having fewer opportunities to play and exercise at school. Although many experts believe that exercise alone is not terribly effective at causing weight loss for adults, it can make a major difference in children. Children are growing rapidly, and significant increases in physical activity can be enough to make their weight come back in line with their height as they grow. Physical activity produces many health benefits that can prevent obesity, including better sensitivity to insulin and better cardiovascular function. Exercise also builds muscle, which burns energy even at rest.
Other factors that affect childhood obesity include an inherited tendency toward weight gain; mental illness; binge eating disorder; eating in response to stress, boredom, or loneliness; poor sleeping habits; and having at least one parent with obesity. A study published in 2018 found that parents tend to underestimate their children's weights and often do not recognize when a child has a weight problem.
In rare cases, medical or genetic disorders can cause obesity. For example, Prader-Willi syndrome is a genetic disorder that causes an uncontrollable urge to eat. The only way to prevent a person with Prader-Willi disorder from constant eating is to keep them in an environment where they have no free access to food. Other genetic and hormonal disorders (e.g., hypothyroidism) can cause obesity. Some brain tumors can as well. Certain medications also can cause weight gain (for example, cortisone, tri-cyclic antidepressants), but these situations are the exception. Researchers estimate that fewer than 10% of cases of childhood obesity are associated with hormonal or genetic causes. Most children are too heavy because of a poor diet.
The most obvious symptom of obesity is an accumulation of body fat. Other symptoms associated with obesity involve changes in body chemistry. Some of these changes cause disease in children, whereas others put the child at risk for developing health problems later in life. Children who are obese are at increased risk of:
Children with obesity and their parents may be referred to a registered dietitian or nutritionist who can help them develop a plan to replace poor foods with nutrient-rich foods that are less likely to make them gain weight. Nutrition education usually involves the entire family. Children may be asked to keep a food diary to record everything that they eat to determine what changes in behavior and diet need to be made. Typically, children are encouraged to increase their level of physical activity rather than to drastically reduce calorie intake. Lifestyle-based interventions can be effective; research published in 2017 indicated that more hours spent on intervention and greater involvement of family members increased the likelihood of success.
Drug therapy and weight-loss surgery are rarely used in children, except in the most extreme cases of health-threatening obesity when other methods of weight control have failed. Some obese children who have developed diabetes take drugs such as metformin or orlistat to control their blood sugar and insulin levels, but using these drugs is associated with only small weight reductions. Some teenagers may benefit from joining a structured weight-loss program such as Weight Watchers or Jenny Craig. Others may prefer a low-carbohydrate diet program such as Atkins. They should check with their physicians before joining.
Children do sometimes grow out of obesity. In some cases, children with obesity who take up a sport and go through puberty at the same time may “grow into” their weight.
Teaching children how to eat a healthy diet sets a framework for their lifetime eating habits. A nutritionist or dietitian can help a family to understand how much and what kinds of food are appropriate for their child's age, weight, and activity level.
The American Heart Association has adapted the following dietary suggestions for children over two. Separate guidelines exist for infant nutrition.
The recommendation of a low-fat diet is not universally accepted among those who work with obese children. Some physicians use low-carbohydrate diets to treat obese patients.
It is often difficult for parents to understand how much food their child should eat at a particular age. Parents tend to overestimate the amount of food small children need. The daily amounts of some common foods that meet the American Heart Association guidelines for different ages are based on children who are sedentary or physically inactive. Active children will need more calories and slightly larger amounts of food. Calorie and serving recommendations are as follows:
Children who are overweight or obese may have accompanying psychological and social problems that may be helped with psychotherapy in addition to nutritional counseling. Cognitive-behavioral therapy (CBT) is designed to confront and change thoughts and feelings about one's body and behaviors toward food. CBT is relatively short-term and does not address the origins of those thoughts or feelings. CBT may include strategies to maintain self-control with regard to food. Family therapy may help children who overeat for emotional reasons related to conflicts within the family. Family therapy teaches strategies for reducing conflict, disorder, and stress that may be factors in triggering emotional eating.
The younger the child is when weight control strategies begin, the better the chance that the child will be able to maintain a normal weight. When it comes to weight control, one advantage children have over adults is that they grow. Children who can maintain their weight without gaining may grow into a normal weight as they becomes taller.
Parents need to be careful about how they approach weight loss in children. Critical comments about weight from parents or excess zeal in putting their child on a rigorous diet can trigger eating disorders such as anorexia nervosa or bulimia nervosa in some children, especially adolescent girls. Instead of placing their child on a diet, parents should promote healthy eating and prepare meals that include lots of fruits and vegetables, whole grains, and low-fat dairy and protein. It is helpful for parents to lead by example, so that the child does not feel isolated. Criticism and focus on losing weight as opposed to getting healthy may lead to a negative body image.
Children who remain overweight or obese have a much greater likelihood of being overweight or obese adults with all the health problems that obesity brings. Studies have found that 26%–41% of preschoolers who are obese become adults who are obese. In school-aged children, 42%–63% of children with obesity become adults who are obese. The relationship between obesity in early life and adulthood is strongest for adolescents, so it is important to deal with childhood obesity as soon as possible.
Parents must take the lead in preventing obesity in children. Helping children develop good eating habits when they are young may help them carry such practices into adult life. Some of the ways parents can promote healthy habits are:
See also Binge eating ; Body image ; Body mass index ; Calories ; Childhood nutrition ; Children's diets ; Diabetes mellitus ; Eating disorders ; Obesity ; School lunches .
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Tish Davidson, AM
Revised by Amy Hackney Blackwell, PhD