In 1999, 13% of children aged 6 to 11 years and 14% of adolescents aged 12 to 19 years in the United States were overweight. This prevalence has nearly tripled for adolescents in the past 2 decades. Risk factors for heart disease, such as high cholesterol and high blood pressure, occur with increased frequency in overweight children and adolescents compared to children with a healthy weight. Type 2 diabetes, previously considered an adult disease, has increased dramatically in children and adolescents. Overweight and obesity are closely linked to type 2 diabetes. Overweight adolescents have a 70% chance of becoming overweight or obese adults. This increases to 80% if one or more parent is overweight or obese. Overweight or obese adults are at risk for a number of health problems including heart disease, type 2 diabetes, high blood pressure, and some forms of cancer. The most immediate consequence of overweight as perceived by the children themselves is social discrimination. This is associated with poor self-esteem and depression.
Defining Obesity in Children and Adolescents
Obesity is defined as an excessive accumulation of body fat. Obesity is present when total body weight is more than 25 percent fat in boys and more than 32 percent fat in girls (Lohman, 1987). Although childhood obesity is often defined as a weight-for-height in excess of 120 percent of the ideal, skinfold measures are more accurate determinants of fatness (Dietz, 1983; Lohman, 1987). A trained technician may obtain skinfold measures relatively easily in either a school or clinical setting. The triceps alone, triceps and subscapular, triceps and calf, and calf alone have been used with children and adolescents. When the triceps and calf are used, a sum of skinfolds of 10-25mm is considered optimal for boys, and 16-30mm is optimal for girls (Lohman, 1987).
Causes of Childhood Obesity
As with adult-onset obesity, childhood obesity has multiple causes centering around an imbalance between energy in (calories obtained from food) and energy out (calories expended in the basal metabolic rate and physical activity). Childhood obesity most likely results from an interaction of nutritional, psychological, familial, and physiological factors.
• The Family
The risk of becoming obese is greatest among children who have two obese parents (Dietz, 1983). This may be due to powerful genetic factors or to parental modeling of both eating and exercise behaviors, indirectly affecting the child’s energy balance. One half of parents of elementary school children never exercise vigorously (Ross & Pate, 1987).
• Low-energy Expenditure
The average American child spends several hours each day watching television; time which in previous years might have been devoted to physical pursuits. Obesity is greater among children and adolescents who frequently watch television (Dietz & Gortmaker, 1985), not only because little energy is expended while viewing but also because of concurrent consumption of high-calorie snacks. Only about one-third of elementary children have daily physical education, and fewer than one-fifth have extracurricular physical activity programs at their schools (Ross & Pate, 1987).
Since not all children who eat non-nutritious foods, watch several hours of television daily, and are relatively inactive develop obesity, the search continues for alternative causes. Heredity has recently been shown to influence fatness, regional fat distribution, and response to overfeeding (Bouchard et al., 1990). In addition, infants born to overweight mothers have been found to be less active and to gain more weight by age three months when compared with infants of normal weight mothers, suggesting a possible inborn drive to conserve energy (Roberts, Savage, Coward, Chew, & Lucas, 1988).
- Endogenous Causes of Childhood Obesity
Increased TSH, decreased thyroxine (T4) levels
Abnormal dexamethasone suppression test; increased 24-hour free urinary cortisol level
Increased plasma insulin, increased C-peptide levels
Hypocalcemia, hyperphosphatemia, increased PTH level
Presence of hypothalamic tumor, infection, syndrome trauma, vascular lesion
- Genetic syndromes & Associated characteristics
Obesity, unsatiable appetite, mental retardation, hypogonadism, strabismus
Obesity, mental retardation, pigmentary retinopathy, hypogonadism, spastic paraplegia
Obesity, retinitis pigmentosa, deafness, diabetes mellitus
Obesity, mental retardation, hypogonadism, hypometabolism, epilepsy
Truncal obesity, mental retardation, hypotonia, hypogonadism
Short stature, undifferentiated gonads, cardiac abnormalities, webbed neck, obesity, 45, X genotype
Muscular hypertrophy, acromegalic appearance, liver enlargement, acanthosis nigricans, insulin resistance, hypertriglyceridemia, mental retardation
Gigantism, exomphalos, macroglossia, visceromegaly
Cerebral gigantism, physical overgrowth, hypotonia, delayed motor and cognitive development
Infant overgrowth syndrome, accelerated skeletal maturation, unusual facies
Mental retardation, microcephaly, skeletal abnormalities, hypogonadism, brachymetapody
- Gene associations
TSH=thyroid-stimulating hormone; PTH=parathyroid hormone.
DETERMINATION OF OVERWEIGHT IN CHILDREN AND ADOLESCENTS
Doctors and other health care professionals are the best people to determine whether your child or adolescent’s weight is healthy, and they can help rule out rare medical problems as the cause of unhealthy weight. A Body Mass Index (BMI) can be calculated from measurements of height and weight. Health professionals often use a BMI “growth chart” to help them assess whether a child or adolescent is overweight. A physician will also consider your child or adolescent’s age and growth patterns to determine whether his or her weight is healthy.
Body mass index (BMI)
This measure is used to assess weight relative to height. It is the same as the body mass index used to identify adult obesity. It is defined as weight in kilograms divided by height in meters squared (kg/m2). It also can be calculated in pound and inches. BMI is closely related to body fat percentage but is much easier to measure. BMI is the standard for defining obesity in adults, but its use in children is not accepted universally. The Centers for Disease Control and Prevention (CDC) suggests two levels of concern for children based on the BMI-for-age charts. At the 85th percentile and above, children are “at risk for overweight” and at the 95th percentile or above, they are “overweight.” The American Obesity Association defines those children above the 95th percentile as “obese,” which corresponds to a BMI of 30 (considered obese in adults).
To calculate a child’s body mass index, follow these steps:
1• Multiply the child’s weight in pounds by 705
2• Then divide by the child’s height in inches
3• Divide this by the height in inches again
- Components of a Successful Weight Loss Plan
Reasonable weight-loss goal:
Initially, 5 to 10 lb, or a rate of 1 to 4 lb per month.
Provide dietary prescription specifying total number of calories per day and recommended percentage of calories from fat, protein and carbohydrates.
Begin according to child’s fitness level, with ultimate goal of 20 to 30 minutes per day (in addition to any school activity).
Self-monitoring, nutritional education, stimulus control, modification of eating habits, physical activity, attitude change, reinforcements and rewards.
Review family activity and television viewing patterns; involve parents in nutrition counseling.
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