Taylor, Mary Jean PT, MA, PCS; Mazzone, Margaret PT, MS; Wrotniak, Brian H. PT, MS
Obesity, generally defined as a condition of excess adipose tissue associated with adverse health conditions, has risen dramatically in children over the past 40 years.1 Since 1960, obesity has increased 54% in children six to11 years old and 13% in children 12 to17 years old.2,3 The average 12-year-old child in the United States (US) today weighs 11.4 lb more than a 12-year-old child of similar height in 1973.2 Today, one in four children is considered to be overweight and many researchers agree that childhood obesity has reached epidemic proportions in the US.1–4
Body mass index (BMI) is a common clinical ratio of weight to height used as an indirect measure of body composition.1,5–7 BMI is calculated by dividing weight in kilograms by height in meters squared (kg/m2). Many pediatricians will plot BMI values on growth charts much as they do for height and weight. Terms such as “overweight” or “at risk of overweight” are associated with certain BMI values and can be related to population percentiles. A child is considered to be overweight if he or she demonstrates a BMI greater than or equal to the 95th percentile when compared to their age-matched peers. Generally, this relates to a BMI of 28 to 30 or greater depending on the child’s age. If the BMI is greater than the 85th percentile when matched with peers, a child is considered at risk of overweight. Typically, this risk of overweight classification corresponds with BMIs in the range of 24 to 28 kg/m2.1,5–7 The term obesity is often times used interchangeably in the literature in what has been defined here as overweight.
Significant consequences are associated with childhood obesity that affects multiple body systems and the child’s overall health and well-being. Children who are obese are more likely to have hypercholesterolemia and hypertension.8 Onset of non–insulin-dependent diabetes mellitus (NIDDM or type 2 diabetes) is increasing in children who are obese. Pinhas-Hamiel et al9 reports that NIDDM increased 10-fold in children who participated in a community-based study in the Cincinnati area. Over 90% of new patients diagnosed with NIDDM had a BMI greater than the 90th percentile and approximately 40% had a BMI greater than 40 kg/m2. Early menstruation, more common in girls who are obese, occurs when the child reaches approximately 102 lb and more than 22% body fat. Young girls may not be emotionally prepared to understand the changes that are occurring in their bodies.10
With respect to the musculoskeletal system, obese children and adolescents account for two thirds of the cases of slipped capital femoral epiphyses and tibia varum.8 Gallstones, liver fibrosis, and cirrhosis are common gastrointestinal complications associated with childhood obesity.8 Sleep apnea is also more common in children who are obese and has been associated with clinically significant impairments in learning and memory that influence success in school.5
Finally, severe disturbances in body image as well as a decrease in self-esteem often coexist in children who are obese. Mazzone et al.,11using the Childhood Health Questionnaire, measured 12 domains reflecting physical and psychological well-being of 34 children characterized as obese. Perception of well-being in six of the 12 domains fell at or below the 25th percentile when the subjects’ scores were compared to their age-matched peers. Performance in the remaining six domains fell at or below the 50th percentile when compared to age-matched peers.
An estimated 60% of overweight children become overweight or obese adults for whom the health complications are significantly greater with staggering economic costs. The risk of a child becoming obese as an adult is 22 times greater if the child is obese versus nonobese.12 The Surgeon General reports that nearly 300,000 adult deaths in the US each year are associated with obesity and overweight (compared to 400,000 for cigarette smoking).6 Dietz attempted to correlate childhood obesity with adult morbidity and mortality and found increases related to cardiovascular disease, diabetes, and colon cancer12. These findings have been confirmed by others.8,13,14 According to follow-up analysis related to the Bogalusa Heart Study, the single most significant factor to predict mortality in men related to cardiovascular disease was whether the individual was overweight as an adolescent.13 Overweight adults are three times more likely to develop NIDDM if they were overweight as a child.8
In a study of 750,000 men and women reported by the American Cancer Society cancer mortality rates were higher in individuals who were more than or equal to 40% overweight.14 There is also an increase in adverse psychosocial consequences for overweight adults who were overweight as children. Gortmaker et al,15 controlling for baseline family income, education, ethnicity, and self-esteem, reported that women who were overweight as adolescents completed less school, had lower household incomes, were twice as likely to live in poverty, and were less likely to be married than women who became overweight as adults.
Though there has been little analysis of the economic costs associated with childhood obesity, some data are available for economic costs associated with inactivity and obesity in adults. The costs of inactivity and obesity in the US, estimated at $47 billion annually, are similar to the total estimated impact of cigarette smoking.16 An estimated 9.5% of all direct healthcare costs are attributed to physical inactivity and obesity. Greater attention in maintaining and promoting healthy nutritional and physical activity habits among children and their parents is now a priority for the U.S. Department of Health and Human Services and the focus of a public health agenda entitled Healthy People 2010.17 In fact, the increasing trend toward obesity served as the stimulus for establishing goals and objectives related to “stemming the tide” of obesity in Healthy People 2010.
Obesity in children may be attributed to three major factors: genetics, unhealthy eating habits, and lack of physical activity.18–20 Often obese parents have children who are also obese, suggesting that children inherit the genetic tendency to become overweight or obese. Genes for obesity were beneficial thousands of years ago when food supply was not always readily available. This genetic predisposition is no longer beneficial given that food supplies are plentiful and individuals are not as physically active. Further evidence suggests that the American genotype has not changed substantially over the past 40 years and may have little causative effect on the current rapid increase in childhood obesity.18 The more likely explanation for the high prevalence of obesity in children is related to an environment that fosters poor eating habits and a decrease in physical activity.18–20
The relationship between these two factors is best explained within the framework of the energy balance model in which BMI is stabilized when energy intake is balanced by energy consumption or output. This model proposes that if energy intake (dietary calories) is greater than energy output (metabolic rate/activity), then fat is stored and body mass increases.18 The significant rise in BMI among children is compounded when one considers that not only is energy intake increasing but energy output is decreasing (Fig. 1). An increase in energy intake is attributed to an abundance of high fat, energy-dense food; palatable, low-cost, easily available meals; and large portion sizes.
Energy output is decreasing in part because of monumental advances in technology. There is a decrease in physical work required to perform many activities of daily living. Instead of getting off the couch to change the channel on the television (TV), children switch channels using a remote control. Instead of helping to rake leaves, children watch their parents use a leaf blower. Children spend a good portion of their recreational time pursuing activities that are less physically demanding. For many children living in urban environments, access to safe outdoor play habitats that promote physical play is limited.
The average school-age child watches TV or plays video/computer games six hours each day.21 US children spend more time watching TV and playing video games than any other activity except for sleep.21 Studies have shown that metabolic rate is lower when watching TV as compared to quiet rest.22 This lack of activity, combined with both an increased tendency to eat while watching TV and advertisements that promote high-fat nutritional choices, has led pediatricians to recommend limiting TV to two hours or less per day.
Finally, there is an increase in sedentary behaviors. Many children when given the choice will opt to ride an elevator rather than climb the stairs. Children are shuttled by car because it is quicker and perhaps safer than walking or riding bikes. Given that the rise in childhood obesity is related to an increase in energy intake and a decrease in energy output, an effective intervention should address both energy intake and output.
Review of the effectiveness of interventions for childhood obesity is mixed. Owens23 examined the effect of exercise in reduction of body fat and improvement in fitness in a group of children seven to 11 years of age. The experimental group participated in 45 minutes of aerobic activity five times per week for four months while the control received no intervention. Nutrition and diet were not addressed. Significant decrease in body fat and improvement of fitness as measured by changes in submaximal heart rate were apparent in the experimental groups. These same results were challenged by Blomquist et al,24 who measured physical work capacity in children eight to nine years of age. In the Blomquist et al study, the experimental group received two additional gym classes per week for four months (a total of four 45-minute periods per week). There was no significant difference in work capacity when the experimental group was compared to the control group. As with the Owens study, nutrition and diet were not considered. The difference in results between studies may be related to frequency or structure of intervention and thus deserves further review.
Given knowledge of the energy model, the combined effect of diet and exercise compared to just diet or no intervention would be expected to produce more favorable results. Epstein et al25 separated 23 children, eight to 12 years of age into two groups. One group received nutrition and diet information, while the other received nutrition and diet information in addition to aerobic exercise three times per week for six months. There was a significant decrease in BMI and increase in physical work capacity when the combined diet and exercise group was compared to the diet-only group. These positive changes were maintained at re-examination 12 months later. Rocchini et al26 reported similar findings in 63 children ranging in age from 10 to 17 years. Participants were assigned to one of three groups. One group served as a control and received no intervention. The second group received diet information and the third group received diet information and exercise (40 minutes of aerobic exercise three times per week). The intervention was five months in duration. Fitness, as measured by submaximal VO2, was significantly improved in the group that received exercise when compared to the groups who did not exercise. Percentage of body fat was significantly reduced in both groups that received diet information compared to the control group. In a study by Becque et al,27 36 adolescents who were obese were randomly separated into three groups: a control or no intervention group, a diet and behavior group, and a diet, behavior, and exercise group. Participants in the diet group met once per week for 20 weeks. Participants in the diet and exercise group met once weekly with a dietician and three times weekly to exercise for 50 minutes. Becque et al reported that neither body composition nor cardiac risk factors were significantly altered between groups that received no intervention and diet alone. Diet combined with exercise yielded no significant improvement in body composition, but there was significant improvement in blood pressure (BP) and high-density lipoprotein levels.27
Epstein et al28,29 compared the outcome differences of two exercise interventions (an increase in lifestyle activity versus traditional aerobic and callisthenic programs) in two different studies. Increasing lifestyle activity was related to behaviors such as walking instead of riding in a car, taking the stairs instead of using the elevator, and minimizing the use of energy-saving devices. While fitness initially improved more in the children who participated in the traditional exercise program, the percentage of overweight was reduced and maintained over two years in the group that emphasized increasing lifestyle activity.
An additional factor to consider in designing programs to address weight control for children is family involvement in the intervention. A child is predisposed to obesity if he or she has a parent who is obese. This seems logical given that the child lives in an environment where the parent may model and support behaviors that promote weight gain. Epstein et al30 evaluated an intervention aimed at addressing behavior change and weight loss for the child and parent. At five- and 10-year follow-up, the percentage of overweight was significantly decreased in the parent-child group when compared to the control. Further support for family involvement is found in studies that demonstrate that a parent’s activity level is a strong predictor of a child’s activity level.31,32 Theoretically, if a parent is more active, the child is more likely to be active, thus tipping the energy model toward weight maintenance or loss.
After careful review of the literature, we propose that intervention outcome may be most favorable if diet instruction is combined with exercise in a family-centered intervention that motivates and promotes an increase in lifestyle activity. The purpose of this study was to investigate the effect of a family-oriented exercise and education-based intervention on morphology and fitness indicators in children who are overweight.
Participants were recruited for this study from pediatricians, school nurses, notices in local newspapers, and public service announcements on radio and cable TV. Children met the following criteria for participation: chronological age between eight and 15 years, a BMI above the 85th percentile when compared to their age-matched peers, stable vital signs during pretesting, adequate balance and coordination to sit on a therapy ball, sufficient attention to follow instructions in a group setting, and medical consent from the child’s physician to participate.
A repeated-measures design was used with data collection consisting of two baseline, pretest measures and a single posttest measure. Pretest measures were collected twice, separated by approximately one week to evaluate medical and performance stability prior to intervention. Posttest data were collected one week after completion of the eight-week intervention phase. Each testing session was identical and lasted approximately 30 minutes in duration. Testing sessions were scheduled at approximately the same time of day. The same staff performed all data collection procedures at each testing session but were blinded to previous results. Data collected included weight, height, waist and hip girth, systolic and diastolic BP (SBP and DBP, respectively), resting heart rate (RHR), immediate postexercise heart rate (HRfinish), five-minute recovery heart rate (5minHR), and distance walked in six minutes. Data were collected over an 18-month period from two separate intervention sites in western New York State.
Weight was determined using a standard upright scale and was measured to the nearest half pound with value determined when the pendulum held steady in the middle of the gauge. Height was recorded by having the child face away from the measuring stick. Feet were placed hip width apart and child was told to maintain feet flat on the surface of the scale and to stand tall. The head stick was moved so that it was level with the top of the child’s head. Shoes were removed for both height and weight measures. Height was recorded in inches. English standard units of measure were used to better communicate meaningful individual outcomes to parents and physicians following intervention. BMI was used to assess change in morphology. BMI was calculated using the obtained values for weight and height and the following formula:
Waist and hip girth were measured as they are responsive to changes in body morphology. Waist girth is associated with central adiposity. Waist and hip girth measures were obtained in centimeters to the nearest half centimeter using a tape measure. Waistline was defined at the narrowest point between the lower border of the ribs and the iliac crests. If no clear delineation of waistline could be made, waist measurement was taken at the umbilicus. Such modification in procedure for an individual subject was noted and replicated for that individual at subsequent testing sessions. Hip girth was measured in the mid-gluteal region. Waist circumference was divided by hip circumference to determine waist-to-hip ratio. Waist-to-hip ratios are commonly used to determine body type and may be used to determine the individual shape as more like an apple or a pear. When the waist circumference is similar to or larger than the hip, the individual is considered to have an apple shape. This body profile is associated with an increase risk of chronic disease in adults. Correlations between body fat distribution in children (specifically central adiposity) and hypertension, elevated triglycerides, and depressed high-density lipoprotein are emerging in the literature.27,33,34
BP was determined by using a sphygmomanometer and stethoscope. BP was routinely recorded in the brachial artery of the right upper extremity following five minutes of quiet rest while seated on a mat table. Systolic and diastolic values were recorded separately for analysis purposes. RHR was recorded using a polar heart monitor following five minutes of quiet rest while seated in a chair.
Once BP and RHR were recorded, the six-minute walk was administered. Participants were instructed to walk as fast as they could for six minutes without running. The child was directed to stop walking if he or she felt chest pain, shortness of breath, dizziness, or nausea. The course was flat, level, and 280 ft long. The number of laps walked was recorded. Time was called at two minutes (“You have walked two minutes; you have four minutes to go!”), at four minutes (“You have walked four minutes; you have two minutes to go!”), and at five minutes (“You have one minute left!”). At six minutes, the experimenter announced “Stop where you are!” Immediate postexercise heart rate (HRfinish) was recorded from the polar heart monitor and distance to this point was added to the total number of laps times the length of the course in feet. The child returned to a chair and rested for five minutes. Heart rate was again recorded (5minHR) using the polar heart monitor to determine cardiac recovery function.
BP was recorded because it is an important variable associated with cardiovascular health. RHR, HRfinish, and 5minHR were evaluated to determine whether a training effect existed following intervention. The six-minute walk is used to assess functional endurance across the lifespan in healthy individuals as well as individuals with significant pathology.35,36 It is easily administered in a clinical setting, functionally relevant, and requires minimal coordination for the child to complete compared to a step test. No normative data are currently available for children. For this reason, comparisons in distance walked are limited to pre- and posttest performance.
The eight-week group intervention was scheduled twice weekly for 60-minute sessions and comprised both exercise and educational components. The exercise portion was conducted by a physical therapist and incorporated aerobic, stretching, and strengthening routines using therapy balls, weights, and Therabands. Target heart rate and Borg Perceived Exertion Scale (focusing on adjective description rather than numerical value) were consistently used to help participants monitor level of physical work. Instruction on how to work more or less vigorously was included during aerobic and strengthening routines so that participants were challenged at a safe and appropriate level. For example, an individual could increase aerobic activity by moving upper and lower extremities simultaneously through full ranges while bouncing more vigorously. Conversely, to slow their pace, participants might move only their upper or lower extremities while bouncing less vigorously or not at all. The exercise program was structured to create a noncompetitive and engaging environment where the participant felt confident and successful while exercising.
The educational component of the program was designed by physicians, in collaboration with a variety of healthcare professionals including registered dieticians, nutritionists, nurse clinicians, an occupational therapist, and a sports psychologist using guidelines established by the American Academy of Pediatrics, the American Dietetics Association, and the U.S. Department of Health and Human Services. The educational component, which covered a wide range of topics related to health and nutritional information, included risks associated with obesity, the energy balance model, the food pyramid, reading food labels, moderation and proportion of a serving, dining out, and strategies to stay motivated. Weekly thirty minutes of one session was dedicated to an educational topic. The rest of the intervention session and the entire second session of the week was devoted to exercise.
Each child was issued an appropriately sized therapy ball. Children were encouraged to exercise daily and were instructed in a home exercise program using their ball. Strategies to incorporate at least 30 minutes of physical activity into a daily routine were also reviewed. Weekly exercise and nutrition logs were provided so that children and families could monitor progress. This intervention was designed to encourage positive, proactive parental and sibling involvement in both the educational and exercise components forging a “team effort” in addressing the child’s weight issues. The entire family was encouraged to participate in the intervention; however, only data from the child with a weight control concern were collected and analyzed to assess the outcome of intervention.
Descriptive statistics were computed and reviewed. A repeated-measures analysis of variance was calculated to determine whether a difference existed between pretest I, pretest II, and posttest values (p < 0.05). If a significant difference existed, post hoc testing was performed using a Tukey test to determine the source of differences.
Fifty-two children were referred to this program and met the inclusion criteria. For data to be included in the analysis, the child could miss no more than four class sessions. In all, data were analyzed for 41 of the 52 children. Data sets are complete for all dependent variables with exception of waist and hip girths and waist-to-hip ratios. Measurement of these variables was added to the procedure after the start of the study to more thoroughly assess changes in body morphology. Overall, 27 children contributed waist and hip data.
The mean age for participants was 127 months or approximately 10.5 years. Eighteen of the participants were boys and 23 participants were girls. Data were not collected on socioeconomic status or sibling rank. Mean height at the beginning of the program was 57.0 in. (at the 90th percentile for stature) with a mean weight of 139.0 lb (>95th percentile). Mean height at the end of the program was 58.0 in. with a mean weight of 140.0 lb. (Percentiles remained the same.) Descriptive analysis for all dependent variables is provided in Tables 1 and 2. Significant differences between measures across time existed for BMI (p = 0.0001), waist girth (p < 0.0001), hip girth (p < 0.0001), SBP (p = 0.0006), DBP (p = 0.0181), RHR (p = 0.0115), HRfinish (p = 0.0298), and 5minHR (p = 0.0255). There was no significant difference across time for waist-to-hip ratio or distance walked in the six-minute walk. Post hoc testing revealed no significant differences between pretest I and pretest II values. A significant difference did exist when pretest values were compared to post measures for BMI (critical value [CV] = 0.304), waist girth (CV = 1.54), hip girth (CV = 1.04), SBP (CV = 5.17), DBP (CV = 4.67), RHR (CV = 7.36), HRfinish (CV = 8.79), and 5minHR (CV = 4.51).
No difference existed between pretest I and II for all dependent variables, indicating a stable baseline. A significant improvement was noted in BMI, waist and hip girth (Figs. 2 and 3), SBP and DBP, RHR, HRfinish, and 5minHR (Fig. 4) when pretest values were compared to posttest values, supporting the effectiveness of this eight-week intervention. Mean BMI decreased by 0.4. This decrease may be related to a decrease in weight, an increase in height, or a combination of the two. Eleven of the 41 children (or 27%) who participated in the program decreased their BMI by one point or greater. Theoretically, if height was held steady, this would correspond approximately to a four-pound weight loss. This is particularly notable when observed on a child with an average height of 58 in.
Significant decrease in waist and hip girths at posttest further corroborates the positive results indicated by decrease in BMI. Though waist and hip girths decreased over the intervention period, no significant difference in waist-to-hip ratios was noted. This relates to the calculation. Waist girth values were divided by hip girth values to determine the ratio. With a decrease in both the waist and hip girth values, the proportion was essentially unchanged. Waist-to-hip ratios are commonly used to determine body type and may be used to describe the individual as more like a pear or an apple. Individuals who have more of an apple shape or a waist-to-hip ratio greater than eight-tenths are more likely to develop diseases related to obesity. This is of particular interest when matched with the individual’s BMI. Though this is frequently referenced in literature related to adult weight control, little correlation of this ratio is available in the pediatric population and may serve as an interesting point for longitudinal study in the future, particularly as it relates to occurrence of chronic disease or cardiovascular risk factors long term.33,34
At pretest, values for BP were well within a healthy range considering mean age and height. High normal BP is defined as SBP or DBP between the 90th and 95th percentiles.37,38 Hypertension is defined by a SBP or DBP above the 95th percentile. Given mean age and height for this sample, hypertension is defined by a systolic value above 120 and a diastolic value above 80. Mean values at pretest for SBP and DBP were within the range for children identified with obesity by Lurbe et al.33 Values for participants at posttest in this study closely approximated values for children described as nonobese in Lurbe et al.33 A significant decrease in SBP and DBP continues to be associated with a decrease in coronary heart disease risk incidence in adults. The long-term effect of decreases in BP observed in this sample of children is not known. RHR at pretest was within the expected value for a typical 10 year old (70 to 150 bpm).39 Posttest values more closely approximately the lower limit of this range and suggest improved cardiovascular conditioning.
Distance traveled in six-minute walk test did not substantially change when pretest values were compared to posttest values. However, heart rate following the six minutes of heavy work (HRfinish) was significantly lower at posttest compared to pretest values, indicating that the participants were able to accomplish the same amount of physical work but more efficiently from a physiologic perspective. Though the five-minute postexercise heart rate (5minHR) was significantly lower at posttest when compared to pretest values, it is important to note that posttest heart rate after five minutes of rest, following heavy work, did not approximate resting values. Return to resting rate within a five-minute interval has been associated with a well-conditioned cardiovascular system. A suggestion for further study may be to measure the participant at one-minute intervals after completing heavy work and assess and compare how long it takes for the participant to achieve his/her resting value. Additionally, perhaps a longer duration of intervention may produce a more complete conditioning effect.
Improved cardiovascular function is an important first step for these participants. Improvements in BP and in the heart’s resting rate and response to exercise are associated with reduction in heart disease and stroke in adults. It is difficult to recognize what impact this will have for our participants in the long term as there are very limited longitudinal data available to support claims that improving these factors in children reduces cardiovascular disease and stroke into adulthood. This is most likely related to the low incidence of obesity in children 30 years ago. Only now are these questions being raised in the literature. In time, the long-term evidence of interventions that reduce these risk factors in childhood, as well as to what degree they are reduced, will more readily be available. Suffice to say, if participants can maintain improvements in SBP, DBP, RHR, and HRfinish for years to come, susceptibility to chronic disease may be minimized. At a disability level, improved cardiovascular integrity may account for reports of greater ease in climbing multiple flights of stairs between classes at school, increase performance in gym class, and greater success in recreational sports associated with high endurance demands.
Positive changes in morphology and physical conditioning associated with this intervention are similar to previously discussed studies.23,25–29 It is important to note that the intervention period for this study was substantially shorter when compared to the work of other authors. The gains made here, though substantial, are more modest than those reported elsewhere. This raises the question of duration of intervention and the effect that it has on outcome.
Several studies by Epstein et al28–30 have attempted to measure long-term outcome. For the intervention to be judged as successful, a relatively permanent change in physical morphology and fitness is expected. This is best assessed longitudinally. This process is often complicated by participant compliance in returning for posttesting, particularly if the participant feels that he or she has not maintained gains for an extended period once the program has ended. Participants who have continued to be successful are more likely to return for follow-up than those who have not, potentially biasing reports toward a positive outcome. Other intervening factors beyond the control of the experimenter can influence long-term outcome and may include such issues as divorce, family illness or loss, altered parent work schedule, and change and/or conflicts in schools. Although long-term follow-up is not reported here, this is a critical factor in determining whether the intervention has achieved an enduring effect. Attempts to maximize participant long-term compliance with posttesting and control for intervening variables deserve careful consideration in future studies.
Finally, 41 of the 52 children who met the inclusion criteria completed the intervention. This high rate of compliance (79%) may be related to the positive, noncompetitive structure of the program. The physical activities, though vigorous, were engaging, fostering high energy expenditure. As participants became more fit and the exercises more challenging, there was a sense of accomplishment when routines were mastered. For many of the children and their parents, this was the first successful fitness experience that they had encountered.
Because no difference existed between pretest I and II measures for any dependent variables, indicating a stable baseline and a significant improvement was noted in BMI, waist and hip girth, BP, RHR, HRfinish, and 5minHR at the conclusion of the intervention, our results indicate that children who participated in this type of program improve their morphology and physical conditioning.
Childhood obesity is a pressing issue, yet few intervention programs exist for children as they struggle to manage their weight. Physical therapists with knowledge of exercise prescription in collaboration with other healthcare providers may provide a valuable service to these children and their families.
We formally acknowledge the many student volunteers for their unceasing dedication to this project.
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© 2005 Lippincott Williams & Wilkins, Inc.