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The Prevalence of Obesity in the U.S.

Childhood obesity is among the most serious health challenges of the 21st century.

• Over the past three decades, the prevalence of children in the U.S. who are obese has doubled, while the number of adolescents who are obese has tripled.
• About one in eight preschoolers (ages 2 to 5) in the U.S. are obese.
• Children who are overweight or obese as preschoolers are five times as likely as normal-weight children to be overweight or obese as adults.

What Causes Childhood Obesity?

Generally, obesity is thought to be the result of eating too many calories and not getting enough physical activity (too much energy in and too little energy out). However, the actual causes of obesity often are more complex. In fact, a combination of genetics, activity level, diet, and the environment in which a child lives and plays can contribute to weight. For example, if a child has one obese biological parent, the odds are roughly 3:1 that the child will have a BMI in the obese range.

According to the CDC, the environmental factors that may contribute to excess weight in children and adolescents include:

• Greater availability of less healthy foods and sugary drinks.
• Advertising of less healthy foods.
• Lack of daily, quality physical activity in schools.
• No safe and appealing place to play or be active. This is a problem in many communities.
• Limited access to healthy, affordable foods.
• Increasing portion sizes.
• Lack of breastfeeding support.
• Greater exposure to television and media. U.S. children ages 8 to 18 spend an average of 7.5 hours a day using entertainment media, including TV, computers, video games, cell phones, and movies.

For some children, an increase in weight may be caused by a condition or disease.

Diseases and conditions that may cause, or contribute to, weight gain include hypothyroidism, Cushing's syndrome, Prader-Willi syndrome, and Kleinefelter's syndrome.

Leading a sedentary lifestyle may contribute to excess weight in children and adolescents.

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Slipped Capital Femoral Epiphysis

Slipped capital femoral epiphysis (SCFE) is an orthopaedic disorder of the adolescent hip. It occurs when the ball at the head (upper end) of the femur (thighbone) slips off in a backward direction due to weakness of the growth plate. The condition can cause weeks or months of hip or knee pain, and an intermittent limp. In severe cases, the adolescent may be unable to bear any weight on the affected leg.

In this illustration of SCFE, the femoral head has shifted slightly downward off the neck of the bone through the growth plate (arrow).

Courtesy of John Killian, MD, Birmingham, AL

The condition is not rare, and often develops during periods of accelerated growth or shortly after the onset of puberty. Hormonal dysfunction associated with obesity may alter growth plate function in a way that can predispose a child's hip to slip. In addition, the extra weight also may increase the sheer forces across the proximal femoral growth plate contributing to the slip.

Treatment of SCFE usually begins within 24 to 48 hours of diagnosis and consists of stabilizing the slipped growth plate with a screw to prevent further slippage.

In children diagnosed with obesity, it can be more challenging to appropriately position and secure the ball of the femur bone without complications.

Blount's Disease

Blount's disease, or severe bowing of the legs, is another condition in which hormonal changes and increased stress on a growth plate, caused by excess weight, can lead to irregular growth and deformity. Progressive deformity, rather than knee discomfort, is the most common complaint.

An adolescent with Blount's disease.

Courtesy of Texas Scottish Rite Hospital for Children

In younger children and less severe cases, a leg brace or orthotic may correct the problem. However, some children may need surgery. Surgery consists of either:

• Growth modulation. During ths procedure, the surgeon inserts a metal plate and screws around the growth plate, which gradually corrects the bowing over time.
• Tibial osteotomy, in which the surgeon removes a wedge of bone from the outside of the tibia (shinbone) under the healthy side of the knee. When the surgeon closes the wedge, it straightens the leg.

Children diagnosed as overweight or obese have a higher risk of complications related to these procedures, including infection, delayed bone healing, failure of fixation, and recurrence of Blount's disease.

Fractures and Related Complications

Children diagnosed as obese or overweight may have a higher risk for fractures (broken bones) due to stress on the bones or because of weakened bones secondary to inactivity. In addition, these children may have more complications that can delay or alter treatment outcomes.

For example, traditional metal implants may not be sufficiently strong to repair broken or misaligned bones. In addition, crutches may be difficult to use for children who are obese or overweight, and cast immobilization may not sufficiently stabilize broken bones. As a result, surgery is often required in addition to casting.

Flat Feet

Children who are overweight or obese often have painful, flat feet that tire easily and prevent them from walking long distances. Many children with flat feet are treated with orthotics and stretching exercises focused on the Achilles tendon (heel cord).

Because weight loss is often enough to ease the pain of flat feet, low impact weight reduction exercises, such as swimming, may be recommended.

Impaired Mobility

Children diagnosed with obesity often have difficulties with their coordination, called developmental coordination disorder (DCD). The symptoms of DCD may include:

• Clumsiness
• Problems with gross motor coordination such as jumping, hopping, or standing on one foot
• Problems with visual or fine motor coordination, such as writing, using scissors, tying shoelaces, or tapping one finger to another

Developmental coordination disorder may impair or limit a child's ability to exercise, potentially resulting in more weight gain. Physical and occupational therapy may improve DCD.

Anesthesia and Other Surgical/Treatment Complications

Children who are obese have a higher rate of anesthetic complications than normal-weight children. In addition, children diagnosed as overweight or obese are more likely to have diabetes, hypertension, sleep apnea, and other endocrine abnormalities that may affect surgical and other treatment, and ultimately, delay or impair bone healing and a return to normal function.