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The relationship between cardiovascular stress reactivity and carotid artery intima-media thickness (IMT) has been established in adults, but not yet studied in children. Cardiovascular reactivity to an ad lib speech was measured in 20 boys and 20 girls age 11.0 +/- 1.4 years. Measures included heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressure reactivity, and mean common carotid artery IMT. Sequential regression analyses were used to establish the incremental increase in R(2) for the prediction of IMT due to cardiovascular reactivity independent of age, socioeconomic status, race, percentage body fat, and baseline BP or HR. SBP reactivity (beta=0.002, , p<.05), but not DBP reactivity (p=.12) or HR reactivity (p=.82), independently predicted carotid artery IMT. This study provides initial evidence that SBP reactivity is associated with IMT and perhaps the early pathogenesis of cardiovascular disease in childhood.

Objective: Children with cerebral palsy (CP) are smaller than normally growing children.. The association between the growth hormone (GH) axis and growth in children with CP during puberty is unknown. We compared growth and markers of the GH axis in pre-pubertal and pubertal children with moderate to severe CP and without CP over a three-year period., Study Design: Twenty children with CP, ages 6-18, Gross Motor Function Classification System levels III-V, were compared to a group of sixty-three normally growing children of similar age. Anthropometry, Tanner stage, bone age, and laboratory analyses were performed every six months for three years. Laboratory values included spontaneous overnight GH release, fasting IGF-1 and IGFBP-3. Repeated measures models were used to evaluate interactions among Tanner stage and group (children with CP vs. reference children), taking into account gender, age, and nutritional status., Results: Children with CP grew more slowly than those without CP at all Tanner stages (p<0.01). Patterns of IGF-1 and GH secretion in children with CP were similar to those of the reference group; however, the concentrations of IGF-1 (p<0.01) and GH (p<0.01) were lower in girls with CP, with a similar trend for boys (p=0.10 and 0.14, respectively)., Conclusions: Diminished circulating IGF-1 and GH concentrations may explain the differences in growth between the two groups.

The rate of habituation to food is inversely related to energy intake, and overweight children may habituate slower to food and consume more energy. This study compared patterns of sensitization, as defined by an initial increase in operant or motivated responding for food, and habituation, defined by gradual reduction in responding, for macaroni and cheese and pizza in overweight and non-overweight 8-12 year-old children. Non-overweight children habituated faster to both foods than overweight children (p = 0.03). All children recovered motivated responding for a new food (chocolate). Overweight children consumed more energy than non-overweight children (p = 0.0004). Children who showed a sensitization in responding consumed more food (p = 0.001), and sensitization moderated the effect of overweight on habituation, with slower habituation for overweight children who sensitized (p < 0.0001). This study replicates previous data on overweight/non-overweight differences in habituation of food and of energy intake, and provides new information that individual differences in sensitization and habituation of motivated responding to food cues may be associated with a sustained motivation to eat, resulting in greater energy intake.

Sitting on a therapy ball or standing may be a passive means of increasing energy expenditure throughout the workday. The purpose of this study was to determine the energy expenditure and liking of performing clerical work in various postures. Subjects included 24 men and women employed in sedentary clerical occupations. Energy expenditure was measured while word processing in three standardized postures; sitting in an office chair, sitting on a therapy ball, and standing. Adults ranked their comfort, fatigue, and liking of each posture and were asked to perform their choice of 20 min of additional clerical work in one of the postures. Energy expenditure was 4.1 kcal/h greater (p or= 0.48). Subjects also liked sitting on a therapy ball as much as sitting in an office chair and liked sitting on a therapy ball more than standing (p

Purpose: To test the validity of the Cart and Load Effort Rating (CALER) and OMNI bike RPE scales., Methods: Children (16 boys aged 9.5 +/- 0.7 and 16 girls aged 9.4 +/- 0.8) performed a progressive exercise test on a cycle ergometer to exhaustion. Random effects models and correlation analysis were used to determine the association of the undifferentiated perceived exertion from the CALER and OMNI bike scales with heart rate and V O2 for concurrent validity and the association of the CALER scale with the validated OMNI bike scale for construct validity. Tests of proportions were performed to compare the proportion of maximal RPE scale (CALER, OMNI bike) with the proportion of maximal heart rate achieved during the final stage of the exercise test., Results: Concurrent validity of the CALER and OMNI bike scales was established, as increases in scores of both scales were associated with (P < or = 0.001 regression) increases in heart rate (r = 0.88 and 0.89) and V O2 (r = 0.92 and 0.93). Construct validity of the CALER scale was established through a significant (P < or = 0.001 regression) relationship with the OMNI bike scale (r = 0.93). The proportion of maximal CALER (75 +/- 20%) and OMNI bike (74 +/- 19%) scales were less (P < or = 0.001) than the peak percentage of the predicted maximal heart rate (94.5 +/- 3%)., Conclusions: Validity for both the CALER and OMNI bike RPE scales was established for a progressively increasing exercise paradigm. However, the proportion of maximal perceived exertion scores from both scales was lower than the proportion of predicted maximal heart rate achieved during the final stage of the exercise test.

This study determined whether liking and relative reinforcing value (RRV) of physical activity were associated with time youth spend in moderate-to-vigorous physical activity (MVPA). Boys (n=21) and girls (n=15) age 8 to 12 years were measured for height, weight, aerobic fitness, liking and RRV of physical activity, and minutes in MVPA using accelerometers. Independence of liking and RRV of physical activity was established by a low correlation (r=0.08, p=0.64). Using MVPA as the dependent variable and hierarchical regression to control for individual differences in age, aerobic fitness, and time the accelerometer was worn in step 1 (R(2) of 0.60 for step 1), addition of liking and RRV of physical activity in step 2 produced an incremental increase in R(2) of 0.12 (p<0.01). When using median splits of the RRV and liking data to form subject groups, children with both a high liking and RRV of physical activity participated in greater (p< or = 0.02) MVPA (1340+/-70 min/week) than children with high RRV-low liking (1040+/-95 min/week), low RRV-high liking (978+/-88 min/week), or low RRV-low liking (1007+/-68 min/week) of physical activity. Thus, liking and RRV of physical activity are independently associated with MVPA. The combination of a high reinforcing value and liking of physical activity is associated with 33% greater participation in MVPA.

Objective: To assess the effects of reducing television viewing and computer use on children's body mass index (BMI) as a risk factor for the development of overweight in young children., Design: Randomized controlled clinical trial., Setting: University children's hospital., Participants: Seventy children aged 4 to 7 years whose BMI was at or above the 75th BMI percentile for age and sex., Interventions: Children were randomized to an intervention to reduce their television viewing and computer use by 50% vs a monitoring control group that did not reduce television viewing or computer use., Main Outcome Measures: Age- and sex-standardized BMI (zBMI), television viewing, energy intake, and physical activity were monitored every 6 months during 2 years., Results: Children randomized to the intervention group showed greater reductions in targeted sedentary behavior (P < .001), zBMI (P < .05), and energy intake (P < .05) compared with the monitoring control group. Socioeconomic status moderated zBMI change (P = .01), with the experimental intervention working better among families of low socioeconomic status. Changes in targeted sedentary behavior mediated changes in zBMI (P < .05). The change in television viewing was related to the change in energy intake (P < .001) but not to the change in physical activity (P =.37)., Conclusions: Reducing television viewing and computer use may have an important role in preventing obesity and in lowering BMI in young children, and these changes may be related more to changes in energy intake than to changes in physical activity.

Within-session decreases in instrumental responding to obtain food, consistent with habituation, have been reliably demonstrated in adults and children. This study tested the hypothesis that within-session decreases in instrumental responding for food are due to habituation rather than satiation. Thirty-eight 8-12-year-old children performed a computer-based operant task to earn points toward access to potato chips for 20 min, and for chocolate candies for the final 6 min of the session. Portion size of the food reinforcer (75 kcal vs 225 kcal) and food consumption (consumption/no consumption). There was no difference in the rate of response decrease between the two portion size conditions. Both the consumption and non-consumption groups showed response decelerations during the first 20 min, with responses in the consumption group decreasing at a faster rate. When the novel food was presented, participants in all conditions recovered responding. Although satiation may contribute to reductions in motivated responding for food when food is consumed, habituation provides a more complete explanation for the results observed in this study.

Objective: The objective was to compare targeting increased eating of healthy foods vs. reducing intake of high energy-dense foods within the context of a family-based behavioral weight control program., Methods and Procedures: Forty-one 8-12 year-old children >85th BMI percentile were randomly assigned to a 24-month family-based behavioral treatment that targeted increasing fruits and vegetables and low-fat dairy vs. reducing intake of high energy-dense foods., Results: Children in the increase healthy food group showed greater reduction in zBMI compared to children in the reduce high energy-dense food group at 12- (-0.30 zBMI units vs. -0.15 zBMI units, P = 0.01) and 24- (-0.36 zBMI units vs -0.13 zBMI units, P = 0.04) month follow-up. Parents in the increase healthy food group showed greater reductions in concern about child weight (P = 0.007), and these changes were associated with child zBMI change (P = 0.008). Children in the reduce high energy-dense group showed larger sustained reductions in high energy-dense foods (P < 0.05). Baseline levels of high energy-dense foods (P < 0.05), parent food restraint (P = 0.01), parent concern over parent weight (P = 0.01) and parent acceptance of the child (P < 0.05) moderated child zBMI change, with greater sustained reductions in zBMI for children in the increase healthy food group for each measure. Parent zBMI change followed the same pattern as child changes, and parent and child zBMI changes were correlated (P < 0.001)., Discussion: Focusing on healthy food choices within an energy restricted diet may be useful in family-based weight control programs.

Objective: The primary objective was to examine the associations between social context (the presence of peers, friends, and family members) and physical activity intensity for overweight and lean girls and boys., Methods: Participants for this study included 10 boys (M = 13.4 years; SD = .8) and 10 girls (M = 13.8 years; SD =. 8). Twelve participants were between the 15th and the 85th BMI percentile (eight girls, four boys) and eight youth were at or above the 85th BMI percentile (six boys, two girls). Participants reported on their activity intensity and whether the activity was solitary or with others for seven consecutive days., Results: Children were more likely to report more intense physical activity when in the company of peers or close friends. Overweight children reported greater physical activity when in the presence of peers than did lean children; however, overweight children also reported more time spent alone., Conclusions: Taken together, findings highlight the importance of considering peer relationships in studies of physical activity and childhood "obesity".

Objective: The purpose of these studies was to test the hypothesis that dietary variety decreases the rate of habituation and increases energy intake in children., Design: In Experiment 1, salivation in response to the same or a variety of food cues was measured followed by consumption of the study food(s). In Experiment 2, children responded in a computer task to earn points for the same or a variety of low or high energy density foods, which were then consumed., Main Outcome Measures: Salivation, number of responses, and energy intake were measured., Results: Participants in the same groups habituated faster than those in the variety groups (p = .05), and in Experiment 2, the effect of variety was independent of energy density. Participants in the variety groups also consumed more energy than those in the same groups in both experiments (p = .05)., Conclusions: Dietary variety disrupted habituation and increased energy intake in children. In addition, the response to dietary variety was independent of energy density, suggesting that increasing variety of low energy density foods may increase consumption., ((Copyright) 2008 APA.)

Background: Price can influence food purchases, which can influence consumption. Limited laboratory research has assessed the effect of price changes on food purchases, and no research on individual differences that may interact with price to influence purchases exists., Objective: We aimed to assess the influence of price changes of low-energy-density (LED) and high-energy-density (HED) foods on mother's food purchases in a laboratory food-purchasing analogue., Design: Mothers were randomly assigned to price conditions in which the price of either LED or HED foods was manipulated from 75% to 125% of the reference purchase price, whereas the price of the alternative foods was kept at the reference value. Mothers completed purchases for 2 income levels ($15 or $30 per family member)., Results: Purchases were reduced when prices of LED (P < 0.01) and HED (P < 0.001) foods were increased. Maternal BMI interacted with price to influence purchases of HED foods when the price of HED foods increased (P = 0.016) and interacted with price to influence purchases of LED foods when the price of HED foods increased (P = 0.008)., Conclusion: These results show the relevance of considering price change as a way to influence food purchases of LED compared with HED foods and the possibility that individual differences may influence the own-price elasticity of HED foods and substitution of LED for HED foods.

Objective: The relationship between stress reactivity and total or central adiposity in children has not been widely studied. Data from two studies were combined to determine the relationship between reactivity to interpersonal stress and the adiposity of children., Research Methods and Procedures: Stress reactivity to an interpersonal stressor (speech) was measured in 36 boys (9.8 +/- 1.3 years of age) and 27 girls (9.3 +/- 1.3 years of age). Total adiposity (percentage body fat) was estimated from skinfolds and central adiposity from the abdominal girth. Multiple regression was used to establish the associations of change in perceived stress and heart rate reactivity with adiposity. Age, sex, ethnicity, and baseline perceived stress and heart rate served as covariates for total adiposity. Fat mass was included as an additional covariate for the prediction of log abdominal girth (central adiposity)., Results: Based on adjusted beta-weights, change in perceived stress (beta = 1.13, p

Objective: Family-based treatments for pediatric obesity were developed over 25 years ago. Over that time, youth have become more obese and the environment more obesiogenic, which may influence efficacy of pediatric weight control. Mixed-effects regression models were used to compare the efficacy of programs initiated 20 to 25 years ago to current programs through 24-month follow-up, as well as to reanalyze 10-year outcomes of previous research using contemporary measures and analytic strategies., Main Outcome Measures: z-BMI and percent overweight., Results: Results showed significant reductions over time, with no differences in z-BMI change for older versus contemporary studies. Age was a predictor of z-BMI up to 24 months, with younger children showing larger change. Mixed-effects regression models replicated previous long-term effects of family-based interventions. Gender was a predictor of long-term z-BMI change, with girls benefiting more over time than did boys., Conclusion: The efficacy of the family-based behavioral approach to treating pediatric obesity replicates over a 25-year period. Challenges in evaluating treatment effects over time are discussed. Ideas for studying choice of treatments that vary in effect size and for strengthening family-based behavioral treatments are noted., (Copyright 2007 APA.)

Our objective was to compare three BMI-based adiposity measures to assess change in pediatric weight control: LMS z-BMI, BMI sympercent, and percent overBMI. Comparison 1 presents changes of +1.0, -1.0, and -2.0 BMI units for 36 hypothetical children (7-, 11-, and 15-year-old children with BMI values from 19-39 kg/m(2)). Comparison 2 presents effect sizes over 12 months and the relationship between baseline and change for 140 8-12-year-old children with BMI values ranging from 21 to 37 kg/m(2). Comparison 1 showed smaller changes in z-BMI than BMI sympercent or percent overBMI for equal changes in BMI when initial BMI values are greater. Comparison 2 showed similar effect sizes for the three measures, since there is a reduction in both standard deviation and magnitude of LMS z-BMI values as the BMI values increase. The three measures perform differently when considering the relationship of initial value to change. Initial percent overBMI shows a negative relationship with change, as heavier children show larger changes, LMS z-BMI shows a positive relationship, as children with lower baseline values show larger changes, and BMI sympercent changes were inconsistently related to baseline BMI sympercent values. Although all three measures result in similar effect sizes when evaluating treatment over time, we conclude that LMS z-BMI is less appropriate for comparing individuals and percent overBMI is the only measure that shows heavier children have greater change.

We have shown that physiological and behavioral responses habituate to food stimuli and recover when novel stimuli are presented. In addition, physiological responses in obese adults habituate slower to repeated food stimuli than those in non-obese individuals, which is related to greater energy intake. The purpose of this study was to test the hypothesis that instrumental responding in overweight children habituates slower to food cues than in their non-overweight peers. Children were provided the opportunity to work for access to cheeseburger for 10 2-min trials, followed by French fries for 3 2-min trials. Results showed that children who had a body mass index (BMI) at or above the 85th BMI percentile (at risk for overweight; n=17) habituated slower than those with a BMI percentile less than the 85th BMI percentile (non-overweight; n=17). Response recovery to French fries did not differ between groups. Overweight children consumed significantly more grams of food and more energy than non-overweight children. When taken together, these data show that habituation may be an important individual difference characteristic that differentiates overweight from non-overweight children. Implications of this for prevention and treatment of obesity are discussed.

Background: Recruitment of participants for clinical trials requires considerable effort and cost. There is no research on the cost effectiveness of recruitment methods for an obesity prevention trial of young children., Methods: This study determined the cost effectiveness of recruiting 70 families with a child aged 4 to 7 (5.9+/-1.3) years in Western New York from February 2003 to November 2004, for a 2-year randomized obesity prevention trial to reduce television watching in the home., Results: Of the 70 randomized families, 65.7% (n=46) were obtained through direct mailings, 24.3% (n=17) were acquired through newspaper advertisements, 7.1% (n=5) from other sources (e.g., word of mouth), and 2.9% (n=2) through posters and brochures. Costs of each recruitment method were computed by adding the cost of materials, staff time, and media expenses. Cost effectiveness (money spent per randomized participant) was US $0 for other sources, US $227.76 for direct mailing, US $546.95 for newspaper ads, and US $3,020.84 for posters and brochures., Conclusion: Of the methods with associated costs, direct mailing was the most cost effective in recruiting families with young children, which supports the growing literature of the effectiveness of direct mailing.

Background: Interactive video games are a popular alternative to physical activity in youth. One advancement in computer games are interactive games that use physical activity as a game playing controller, combining exercise and entertainment, or exertainment., Purpose: This study tested the reinforcing value and activity levels of interactive dance and bicycle race games in 18 overweight and 17 nonoverweight 8- to 12-year-old youth., Methods: Reinforcing value was studied using a behavioral choice paradigm that provided children the opportunity to respond on progressive ratio schedules of reinforcement for a choice of either playing the video dance or bicycle game using a handheld video game controller or one of three options: dancing or bicycling alone, dancing or bicycling while watching a video, or playing the interactive dance or bicycle game. Reinforcing value was defined in relationship to the amount of responding children engaged in for either choice., Results: Results showed the interactive dance game was more reinforcing than dancing alone or dancing while watching the video (p = .003), but there was no difference across bicycling conditions. Nonoverweight youth were more active when given the opportunity to play the interactive dance game than overweight children (p = .05)., Conclusions: These results suggest that children may be motivated to be active when given the opportunity to play an interactive dance game.

Background: Sedentary activities, such as watching television, may disrupt habituation to food cues, thereby increasing motivation to eat and energy intake., Objective: These experiments were designed to examine the effect of television watching on habituation of ingestive behavior in children., Design: In experiment 1, all children worked for access to cheeseburgers in trials 1-7 (habituating stimulus). In trials 8-10, children in the control group continued to work for cheeseburgers without any dishabituating stimuli, whereas children in the other groups received either a novel food (French fries) or television as dishabituating stimuli. Responding for food and amount of food eaten were measured. In experiment 2, all children had access to 1000 kcal of a preferred snack food. One group watched a continuous television show, and the control groups either watched no television or watched a repeated segment of a television show, which controls for the television stimulus but requires reduced allocation of attention., Results: In experiment 1, both the novel food and the television watching groups reinstated responding for food (P = 0.009) and increased the amount of energy earned (P = 0.018) above the level of the control subjects. In experiment 2, the continuous television group spent more time eating (P < 0.0001) and consumed more energy than the no television and the repeated segment groups (P = 0.007)., Conclusion: These experiments show that television watching can dishabituate eating or disrupt the development of habituation, which may provide a mechanism for increased energy intake associated with watching television.

Background: To increase participation in physical activity, it is important to understand the factors associated with a child's choice to be physically active or sedentary. The neighborhood and home environments may be related to this choice., Purpose: To determine whether the neighborhood environment or number of televisions in the home environment are independently associated with child physical activity and television time., Methods: The associations of the neighborhood and home environments on active and sedentary behaviors were studied in 44 boys and 44 girls who wore accelerometers and recorded their television watching behaviors. Neighborhood environment variables were measured using extensive geographic information systems analysis., Results: Hierarchical regression analyses were used to predict physical activity after controlling for individual differences in age, socioeconomic status, percentage overweight, and time the accelerometer was worn in Step 1. Sex of the child was added in Step 2. A neighborhood design variable, street connectivity, accounted for an additional 6% (p

Objective: To determine associations of the neighborhood and home television environments with young children's physical activity., Method: 32 boys and 27 girls age 4 to 7 years wore accelerometers for 3 weekdays and 1 weekend day. The number of televisions in the home and television watching of the child were monitored using TV Allowance units for 3 weeks. A geographic information system was used to measure neighborhood environment variables., Results: Hierarchical regression analysis was used to predict physical activity, initially controlling for sex, age, socioeconomic status, adiposity, and child television watching in step 1. In step 2, the number of televisions did not significantly increase the amount of variability accounted for in the prediction of physical activity. In step 3, housing density and the interaction of housing density by sex accounted for an incremental 12% (p < 0.05) of the variability and in step 4 percentage park plus recreation area accounted for a further 10% (p < 0.05) of the variability. Greater housing density predicted increased physical activity of boys, but not girls., Conclusion: Neighborhoods with increased proximity between homes and a greater proportion of park area are associated with greater physical activity in young children.

Many young children have televisions in their bedrooms, which may influence the relationship between parental estimate and objective measures of child television usage/week. Parental estimates of child television time of eighty 4-7 year old children (6.0 +/- 1.2 years) at the 75th BMI percentile or greater (90.8 +/- 6.8 BMI percentile) were compared to an objective measure of television time obtained from TV Allowance devices attached to every television in the home over a three week period. Results showed that parents overestimate their child's television time compared to an objective measure when no television is present in the bedroom by 4 hours/week (25.4 +/- 11.5 vs. 21.4 +/- 9.1) in comparison to underestimating television time by over 3 hours/week (26.5 +/- 17.2 vs. 29.8 +/- 14.4) when the child has a television in their bedroom (p = 0.02). Children with a television in their bedroom spend more objectively measured hours in television time than children without a television in their bedroom (29.8 +/- 14.2 versus 21.4 +/- 9.1, p = 0.003). Research on child television watching should take into account television watching in bedrooms, since it may not be adequately assessed by parental estimates.

This study was designed to determine whether the characteristics of the neighborhood environment are related to the substitution of physical activity for sedentary behavior among youth. Fifty-eight 8- to 15-year-old youth were studied in a within-subjects crossover design with three phases: baseline, increased sedentary behavior, and decreased sedentary behavior. The relations between changes in physical activity and design, diversity, and density attributes of the neighborhood environment were determined using random coefficient models. Compared with girls, boys showed greater increases in physical activity when sedentary behaviors were reduced and greater decreases in physical activity when sedentary behaviors were increased. Greater access to parks was associated with greater physical activity when sedentary behaviors were reduced.

Many conditions that delay skeletal maturation also delay the onset of puberty, whereas conditions that accelerate skeletal maturation often hasten the onset puberty, raising the possibility that skeletal maturation influences pubertal onset. To determine whether this concordance is also present in normal children, we analyzed data from 30 normal boys participating in a longitudinal study. Height, weight, and serum testosterone concentrations were assessed every 6 months and bone age (Fels method) every year. Pubertal onset was defined by serum testosterone > or =30 ng/dL. The variability in bone age at onset of puberty was not less than the variability in chronological age. In addition, there was no significant correlation between skeletal advancement and pubertal advancement (r=0.01, P=0.9). Similarly, there was not a significant correlation between pubertal advancement and height age advancement, weight age advancement, or BMI age advancement. Our findings do not support the hypothesis that skeletal maturation directly influences the age of pubertal onset in normal boys.

To our knowledge, there are no data on parental influences on child purchasing behavior of healthy or unhealthy foods. Mothers and children in ten families were given 5.00 US dollars to purchase portions of preferred fruits/vegetables and high energy-dense snack foods for each of ten trials of price manipulations. For five of the trials the price of the fruit/vegetable increased in price from 0.50 US dollars to 2.50 US dollars (in 0.50 US dollar increments), while the price of the energy-dense snack food remained constant at 1.00 US dollar. For the remaining five trials, the commodity that previously rose in price remained constant at 1.00 US dollars and the other commodity varied from 0.50 US dollars to 2.50 US dollars. Same-price elasticity was shown for both the child and parent purchases, and parent purchases were significantly related to child purchases of both healthy (regression estimate = 0.46, p < 0.001) and unhealthy (regression estimate = 0.12, p = 0.036) foods. Children's purchases of unhealthy snack food items were positively related to family socioeconomic status, and negatively related to child age. These results indicate that parental food choice and purchasing behaviors may play a role in the development of children's purchasing of both healthy and unhealthy foods.

Salivary responses habituate to repeated presentations of food cues, and these responses recover when new food stimuli are presented. Research suggests that within-session changes in motivated responding for food may also habituate, and motivated responding may, therefore, recover when new foods are presented. The purpose of this study was to evaluate similarities in the pattern of salivation and motivated responding for a cheeseburger stimulus in children, followed by either a novel stimulus (French fries) or another cheeseburger trial. The order of the task (salivation or motivation) was counterbalanced over days. Salivation and motivated responding for cheeseburger were reliably reduced over seven trials, and responses recovered after presentation of French fries on trial 8. Random regression models showed a significant relationship between the rate of change in motivated responding and salivation. These results provide additional support for similarities in processes that regulate salivation and motivated responding for food and strengthen support for the hypothesis that changes in motivated responding can be understood by habituation theory.

Purpose: This study was conducted to test the validity of the Pictorial Children's Effort Rating Table (PCERT) and OMNI walk/run scales., Methods: Children (26 boys age 11.2 yr +/- 1.6 and 25 girls age 11.1 yr +/- 1.4) performed a five-stage incremental exertion treadmill test. The undifferentiated perceived exertion from the PCERT and OMNI scales was assessed for construct validity using Pearson correlations with VO(2) and heart rate as criteria and concurrent validity by correlating PCERT and OMNI scores., Results: Increases in PCERT and OMNI scale scores were correlated with increases in VO(2) (r = 0.90 and 0.92) and heart rate (r = 0.89 and 0.92). No difference was found in slope of the PCERT and OMNI scores when regressed against heart rate or VO(2) and the slopes were invariant across sexes. To test concurrent validity of the PCERT and OMNI scales, subject scores at each stage were converted to a percentage of the maximal scale. No effect of sex was noted on perceived exertion (P = 0.32), and the percentage of the maximal PCERT and OMNI scales was almost identical at each stage (P = 0.73)., Conclusions: Validity of both the PCERT and OMNI scales was established for submaximal exercise. PCERT and OMNI scores are not interchangeable because they have different scales, but at a given exercise intensity youth assign similar percentages of the maximal scores.

Integrative neuroendocrine control of the gonadotropic and somatotropic axes in childhood, puberty, and young adulthood proceeds via multiple convergent and divergent pathways in the human and experimental animal. Emerging ensemble concepts are required to embody independent, parallel, and interacting mechanisms that subserve physiological adaptations and pathological disruption of reproduction and growth. Significant advances in systems biology will be needed to address these challenges.

Objective: To examine the effect of adenotonsillectomy (T&A) in children with obstructive sleep-disordered breathing on growth, hyperactivity, and sleep and waking motor activity., Methods: We studied 54 children who were aged 6 to 12 years and had adenotonsillar hypertrophy and an obstructive apnea-hypopnea index of > or =1 before and 12 months after they all received adenotonsillectomy (T&A). We measured their height, weight, percentage overweight (patient BMI - BMI at 50th percentile)/BMI at 50th percentile x 100) and obtained a hyperactivity score from parent report on a standardized behavior questionnaire scale. A subset of 21 of these children were also studied for motor activity by wrist actigraphy for 7 consecutive days and nights before and 12 months after T&A., Results: After T&A, mean obstructive apnea-hypopnea index decreased from 7.6 to 0.6. Height percentile did not change, but weight percentile increased; as a consequence, percentage overweight increased from 32.0% to 36.3%. Hyperactivity scores and total daily motor activity were reduced after T&A. From linear regression, the reduction in hyperactivity scores predicted an increase in percentage overweight. Reduced motor activity was correlated with increased percentage overweight., Conclusions: An increase in percentage overweight after T&A in children with obstructive sleep-disordered breathing is correlated to decreased child hyperactivity scores and to decreased measured motor activity in the subset studied. These associations suggest that the increase in overweight may be attributable to reductions in physical activity and fidgeting energy expenditure.

One way to increase choice of healthy over unhealthy behaviors is to increase the cost of less healthy alternatives or reduce the cost of healthier alternatives. The influence of price on purchases of healthy and unhealthy foods was evaluated in two laboratory experiments. In Experiment 1, thirty-two 10- to 12-year-old youth were given $5.00 and allowed to purchase multiple portions of a healthy food (fruit or vegetable) and a less healthy food (higher-fat snack). The price of one type of food varied from $0.50 to $2.50, while the price of the other type was held at $1.00. Increasing the price of a type of food reduced purchases of that type of food, but did not lead to substitution with the alternative type of food. In Experiment 2, twenty 10- to 14-year-old youth were given $1.00, $3.00, and $5.00 to purchase healthy and unhealthy foods. The price of each food was raised and lowered by 25% and 50%. Raising the price of healthy or unhealthy foods resulted in decreased purchases of those foods, and income available interacted with price to predict the pattern of substitution of alternative foods. These results show the potential for controlled laboratory studies of price and food purchases, and show that the substitution of healthier for unhealthy food is related to available money.

Background: One of the basic principles of behavioral economics interventions is identification of alternative behaviors to compete with the reinforcing value of a highly rewarding commodity., Purpose: Two experiments that attempt to increase alternatives to eating in obese youth are presented., Methods: A randomized, controlled trial was used in Study 1 to compare a comprehensive family-based behavioral treatment program or an experimental treatment that incorporated reinforcing children for engaging in alternative behaviors to eating for 41 overweight 8- to 12-year-old children. Study 2 used a within-subject design with baseline, enriched environment and a second baseline phase to determine the influence of providing activities that compete with eating for 13 overweight 8- to 12-year-old children. Measurements included body mass index (BMI) change, alternatives to eating, eating, and physical activity., Results: In Study 1 both treatments were associated with significant (p < .05) and maintained reductions in z-BMI over the 24 months of observation. The experimental group showed a significantly (p < .05) greater increase in alternatives to eating, and both groups showed significant (p < .05) increases in physical activity. In Study 2 alternative behaviors to eating were increased by almost 1 hr/day (p < .001) but were not associated with significant changes in energy intake or physical activity., Conclusion: These results suggest that using the methods studied, increasing behaviors that could compete with eating did not influence relative weight in a clinical outcome study or energy intake in a controlled field study.

Deconvolution analysis was used to determine 12-hour spontaneous nocturnal growth hormone (GH) secretion and GH half-life in lean (body mass index, <85th percentile; n = 39) and overweight (body mass index, > or =85th percentile; n = 18) youth. The integrated GH concentration, GH burst mass, and half-life were lower (P < .05) in overweight than in lean youth. For each unit increase in percentage of body fat, integrated serum GH concentrations, secretory burst mass, and half-life declined by 83.6 microg/L per minute (r = -0.39, P < .01), 0.22 microg/L (r = -0.28, P < .05), and 0.2 minute (r = -0.38, P < .01), respectively. The effect of overweight on GH secretion was independent of pubertal status. Hierarchical regression models tested the hypothesis that altered GH secretion in youth is more related to total adiposity than abdominal visceral fat. When age, sex, fat-free mass, testosterone, and estradiol were held constant, the sequential addition of abdominal visceral fat did not increase R2 for any GH secretion variable. Sequential addition of percentage of body fat increased R2 (P < .05) for integrated GH concentration, total secretory rate, secretory burst mass, and pulsatile production rate. We conclude that serum GH concentrations are reduced in overweight youth primarily because of reduced GH burst mass with no change in the number of secretory events and secondarily to reduced GH half-life. Based on the model that GH-releasing hormone predominantly increases GH pulse amplitude whereas somatostatin primarily controls GH pulse frequency, these results suggest that overweight in youth diminishes GH-releasing hormone stimulation resulting in truncated GH bursts but does not alter the number of somatostatin withdrawal intervals so that GH burst frequency is conserved.

Background: Youth may choose to be sedentary rather than physically active., Purpose: The purpose of this study was to use behavioral economics methods to investigate how experimental changes in the amount of sedentary behaviors influenced physical activity., Methods: Fifty-eight 8- to 16-year-old youth were studied in a within-subject crossover design with three 3-week phases: baseline, increasing, and decreasing targeted sedentary behaviors by 25% to 50%., Results: At baseline, boys were more active than girls (518.9 vs. 401.2 accelerometer counts/min, p = .02), and obese youth more sedentary than nonobese youth (240.5 vs. 174.4 min/day, p = .003). During the increase sedentary behavior phase, targeted sedentary behaviors increased by 52.1%, with girls increasing sedentary behaviors more than boys (114.7 vs. 79.8 min/day, p = .04). Physical activity decreased (-48.3 counts/min, p < .01) when sedentary behaviors increased, with obese youth decreasing total and moderate to vigorous physical activity (MVPA) more than nonobese youth (-110.4 vs. 8.9 counts/min, p < .001; -3.3 vs. -.03 % MVPA, p = .013). During the decrease sedentary behavior phase, targeted sedentary behaviors decreased by 55.6% from baseline as nonobese youth increased physical activity, whereas obese youth decreased physical activity (55.8 vs. -48.0 counts/min, p = .042; 1.1 vs. -2.1% MVPA, p = .021). Youth who substituted physical activity when sedentary behaviors were increased had greater standardized body mass index (z-body mass index = 1.4 vs. 0.4, p = .018), whereas youth who substituted physical activity when sedentary behaviors were decreased were less active at baseline (396.1 vs. 513.7 counts/min, p = .035)., Conclusions: Behavioral economics provides a methodology to understand changes in physical activity when sedentary behaviors are modified and to identify factors associated with substitution of physically active for sedentary behaviors.

Objective: Better adherence to treatment strategies in family-based behavioral weight control programs may lead to greater weight reduction and improved weight maintenance in youth. This study assessed the influence of child and parent self-reported adherence to behavioral strategies on changes in 2-year child and parent percentage overweight., Research Methods and Procedures: Participants included 8- to 12-year-old children in >or= 85th BMI percentile and their parents from 110 families taking part in two family-based randomized controlled weight control studies. This study examined whether self-reported adherence to behavioral strategies measured at 24 months increased prediction of child and parent percentage overweight change through 24-month follow-up after accounting for other factors that may influence weight change., Results: Child adherence to weighing and to preplanning for celebrations where high-fat foods are served and parent adherence to praising the child and modeling healthy eating habits predicted 24-month child percentage overweight change (p<0.001). Child adherence to recording food and calories and parent adherence to modeling healthy eating habits predicted 24-month parent percentage overweight change (p<0.001). In hierarchical regression models, child weighing and preplanning and parent modeling were significant (p<0.01) incremental predictors (r2 of 24.8%) of 24-month child percentage overweight. Child recording and parent modeling were significant (p<0.01) incremental predictors (r2 of 14%) of parent 24-month percentage overweight change., Discussion: Child and parent adherence to specific components of family-based behavioral weight control treatment are independent predictors of long-term child and parent percentage overweight change.

Objective: Magnesium deficiency has been associated with insulin resistance (IR) and increased risk for type 2 diabetes in adults. This study was designed to determine whether obese children exhibit serum or dietary magnesium deficiency and its potential association with IR., Research Design and Methods: We studied 24 obese nondiabetic children (BMI > or =85th percentile) and 24 sex- and puberty-matched lean control subjects (BMI <85th percentile). We measured serum magnesium, indexes of insulin sensitivity, dietary magnesium intake (using a food frequency questionnaire), and body composition (by air displacement plethysmography)., Results: Serum magnesium was significantly lower in obese children (0.748 +/- 0.015 mmol/l, means +/- SE) compared with lean children (0.801 +/- 0.012 mmol/l) (P = 0.009). Serum magnesium was inversely correlated with fasting insulin (r(s) = -0.36 [95% CI -0.59 to -0.08]; P = 0.011) and positively correlated with quantitative insulin sensitivity check index (QUICKI) (0.35 [0.06-0.58]; P = 0.015). Dietary magnesium intake was significantly lower in obese children (obese: 0.12 +/- 0.004 vs. lean: 0.14 +/- 0.004 mg/kcal; P = 0.003). Dietary magnesium intake was inversely associated with fasting insulin (-0.43 [-0.64 to -0.16]; P = 0.002) and directly correlated with QUICKI (0.43 [0.16-0.64]; P = 0.002)., Conclusions: The association between magnesium deficiency and IR is present during childhood. Serum magnesium deficiency in obese children may be secondary to decreased dietary magnesium intake. Magnesium supplementation or increased intake of magnesium-rich foods may be an important tool in the prevention of type 2 diabetes in obese children.

Responding to food cues may be disrupted by allocating attention to other tasks. We report two experiments examining the effects of allocation of attention on salivary habituation to olfactory plus visual food cues in 8-12-year-old children. In Experiment 1, 42 children were presented with a series of 8 hamburger food stimulus presentations. During each intertrial interval, participants completed a controlled (hard), or automatic (easy) visual memory task, or no task (control). In Experiment 2, 22 children were presented with 10 presentations of a pizza food stimulus and either listened to an audiobook or no audiobook control. Results of Experiment 1 showed group differences in rate of change in salivation (p=0.014). Children in the controlled task did not habituate to repeated food cues, while children in the automatic (p<0.005) or no task (p<0.001) groups decreased responding over time. In Experiment 2, groups differed in the rate of change in salivation (p=0.004). Children in the no audiobook group habituated (p<0.001), while children in the audiobook group did not habituate. Changes in the rate of habituation when attending to non-food stimuli while eating may be a mechanism for increasing energy intake.

Body composition exhibits marked variations across the early human lifetime. The precise physiological mechanisms that drive such developmental adaptations are difficult to establish. This clinical challenge reflects an array of potentially confounding factors, such as marked intersubject differences in tissue compartments; the incremental nature of longitudinal intrasubject variations in body composition; technical limitations in quantitating the unobserved mass of mineral, fat, water, and muscle ad seriatim; and the multifold contributions of genetic, dietary, environmental, hormonal, nutritional, and behavioral signals to physical and sexual maturation. From an endocrine perspective (reviewed here), gonadal sex steroids and GH/IGF-I constitute prime determinants of evolving body composition. The present critical review examines hormonal regulation of body composition in infancy, childhood, and puberty.

Background: Changes in sedentary behavior may be related to changes in energy intake., Objective: The purpose of this study was to investigate how experimental changes in the amount of sedentary behaviors influence energy intake., Design: Sixteen nonoverweight 12-16-y-old youth were studied in a within-subject crossover design with three 3-wk phases: baseline, increasing targeted sedentary behaviors by 25-50% (increase phase), and decreasing targeted sedentary behaviors by 25-50% (decrease phase). Repeated 24-h recalls were used to assess energy and macronutrient intakes during targeted sedentary behaviors. Accelerometers were used to assess activity levels., Results: Targeted sedentary behaviors increased by 81.5 min/d (45.8%) and decreased by 109.8 min/d (-61.2%) from baseline (both: P<0.01). Girls increased sedentary behaviors significantly more than did boys (107.3 and 55.8 min/d, respectively; P<0.01) in the increase phase. Energy intake decreased (-463.0 kcal/d; P<0.01) when sedentary behaviors decreased: the decrease in fat intake was -295.2 kcal/d (P<0.01). No significant changes in energy intake were observed when sedentary behaviors were increased. Youth also increased their activity by 102.4 activity counts min-1d-1 (estimated at 113.1 kcal) when sedentary behaviors were decreased (P<0.05)., Conclusions: Decreasing sedentary behaviors can decrease energy intake in nonoverweight adolescent youth and should be considered an important component of interventions to prevent obesity and to regulate body weight.

Background: The influence of weight loss on insulin resistance was determined in severely overweight (BMI Z-score: 7.3 +/- 0.9 z-units) hyperinsulinemic (mean fasting serum insulin concentration: 33.0 +/- 6.7 muIU/mL) youth., Methods: Eight overweight youth and obese parents were studied at baseline and then at 6 and 12 months after behavioral weight loss therapy. Non-treated lean youth (n = 8) served as controls for normal interval growth. The groups were matched for sex, race, age (10.2 versus 10.1 years), and pubertal maturation, and evaluated for weight, height, blood pressure, and the homeostasis model of insulin resistance (HOMA-IR)., Results: Overweight youth had reductions (p

Background: Family-based behavioral weight control treatment involves the parent in the modification of child and parent eating and activity change., Objective: To assess if parent standardized body mass index (z-BMI) change predicts child z-BMI change., Design: Secondary data analysis based on parent and child z-BMI changes from 3 family-based, randomized, controlled weight control studies. Hierarchical regression models tested whether parent z-BMI change increased prediction of child z-BMI change through treatment and 24-month follow-up beyond other factors that influence child weight change, such as child age, sex, socioeconomic status, and baseline child and parent z-BMI. Differences in child z-BMI change as a function of quartiles of parental z-BMI change were tested using an analysis of covariance., Setting: Pediatric obesity research clinic., Participants: Obese 8- to 12-year-old children and their parents from 142 families who participated in family-based weight control programs., Main Outcome Measures: Child and parent z-BMI changes over time., Results: Parent z-BMI change significantly predicted child z-BMI change for the 0- to 6-month (P<.001) and 0- to 24-month (P <.009) time points. In hierarchical regression models, parent z-BMI change was a significant incremental predictor of child z-BMI change at 6 and 24 months, with the additional r(2) ranging from 11.6% at 6 months (P <.001) to 3.8% at 24 months (P =.02). Parents in the highest quartile of z-BMI change had children with significantly greater z-BMI change than that of children with parents in the other quartiles (P =.01)., Conclusion: Parent z-BMI change is an independent predictor of obese child z-BMI change in family-based behavioral treatment, and youth benefit the most from parents who lose the most weight in family-based behavioral treatments.

Purpose: The number of youth that meet activity guidelines is decreasing and easy access to reinforcing sedentary behaviors competes with increasing physical activity. In the laboratory, open-loop feedback that used pedometer activity counts to gain access to sedentary alternatives doubled physical activity. This study evaluated the influence of open-loop feedback and reinforcement on physical activity and television (TV) time in a small clinical trial., Methods: Children (8-12 yr old) were randomized to an open-loop feedback plus reinforcement intervention (N = 11) or no feedback, no reinforcement control (N = 7). Subjects wore an accelerometer for 6 wk and attended meetings to download the accelerometer. Accumulating physical activity counts gave subjects in the open-loop group access to TV time, controlled by a TV Allowance device, with 400 counts = 1 h of TV. The control group had no feedback for activity and free access to TV., Results: The open-loop group had a 24% increase in physical activity, which was greater (P = 0.02) than the control group. TV time of the open-loop group was reduced by 18% or 20 min x d(-1) whereas the control group increased by 13 min x d(-1), but these were not significant changes. The change in time spent watching television was directly related to the change in BMI z-score (r = 0.69, P = 0.002)., Conclusion: Open-loop feedback increases physical activity in children, thus helping children to achieve physical activity recommendations. Reductions in TV watching may reduce or minimize gains in body weight.

Objective: Rapid synaptic dopamine transport or reduced brain dopamine receptor signaling may influence energy intake. Methylphenidate, a dopamine reuptake inhibitor, increases brain synaptic dopamine and produces anorexia, suggesting that it may reduce energy intake. We investigated the effects of two doses of short-acting methylphenidate on energy intake over one meal in obese adult males., Research Methods and Procedures: Nine obese males (>85th BMI percentile) ingested a placebo or a moderate dose (0.5 mg/kg) or a high dose (1.0 mg/kg) of methylphenidate in a within-subject double-blind acute laboratory study. One hour after ingestion, pizza consumption was measured in a naturalistic laboratory setting., Results: Participants reduced energy intake by 23% for the moderate dose vs. the placebo (p < 0.02), but there was no significant difference for the high dose vs. the moderate dose (p > 0.05). Participants consumed 34% fewer kilocalories after ingesting the lowest effective dose of methylphenidate compared with placebo (725.7 +/- 404.5 vs.1095 +/- 271.1 kcal, p < 0.01). Seven of nine subjects responded to the moderate dose. The increase in perceived drug effect above placebo was correlated with the reduction in energy intake for both the moderate (r = -0.85, p = 0.004) and the high (r = -0.75 p = 0.021) doses. Hunger scores were not different across drug doses or placebo before drug administration., Discussion: Methylphenidate reduced energy intake of a highly palatable food over one meal by one-third in obese adult males. Dopamine transport inhibition may be an effective component of a comprehensive treatment for obesity.

The choice to be physically active or sedentary depends in part on the value of the alternatives that are available. The shift from sedentary to active alternatives may be a function of the value of the sedentary alternatives. To evaluate the influence of the value of the sedentary alternatives on the choice to be physically active or sedentary, 30 nonobese 8-12-year-old youth were randomized in groups that provided a choice between 4 active alternatives or 4 sedentary alternatives (Group 1), their least valued sedentary activity (Group 2), or their most valued sedentary activity (Group 3), on computerized and questionnaire versions of a behavioral choice task. The computer task required participants to work for access to the alternatives. The work required to obtain access to the active alternatives remained constant for all choices, while the work required to gain access to the sedentary alternatives progressively increased. Compared to Groups 1 and 3, participants in Group 2 chose to be sedentary less often as they had to make a choice between being physically active or sedentary on the computerized (p < .005) and the questionnaire version (p < .05) of the behavioral choice task, which correlated r = .54, p < .01. These results suggest interventions designed to increase physical activity by reducing access to sedentary behaviors may need to consider the value of the targeted sedentary behavior and the extent to which the sedentary behaviors compete with physical activity.

Repeated presentation of food cues results in habituation in adults, as demonstrated by a decrement in salivary responding that is reversed by presenting a new food cue in adults. Food reinforced behavior in animals shows the same pattern of responding, with a decrease in responding to obtain the food, followed by a recovery of responding when a new food is presented. The present study assessed whether children would show the same pattern of a decrement of food reinforced responding followed by recovery of responding when a new food is presented for both salivation and food reinforcement tasks. Subjects were assigned to one of two groups that differed in the trial that the new food stimulus was presented to ensure recovery was specific to the introduction of the new food stimulus. In the salivation task, subjects were provided repeated olfactory presentations of a cheeseburger with apple pie as the new food stimulus, while in the food reinforcement task subjects worked for the opportunity to consume a cheeseburger, followed by the opportunity to work for consumption of apple pie. Subjects in both groups showed a decrement in salivary and food reinforced responding to repeated food cues followed by immediate recovery of responding on the trial when a new food was presented. Subjects increased their energy intake by over 30% in the food reinforcement task when a new food was presented. These results are consistent with the general process theory of motivation that suggests that changes in food reinforced responding may be due in part to habituation.

Objective: To determine whether interpersonal stress reduces youths' motivation to exercise in a laboratory setting., Research Methods and Procedures: Physical activity and sedentary behavior were measured in boys and girls across a control day, after reading children's magazines, and on a stress day, after giving a videotaped speech. For one analysis, children were divided into low (n = 12) and high (n = 13) heart-rate reactivity groups based on changes in heart rate to stress. In a second analysis, children were divided into low and high perceived level of stress based on changes in perceived stress. To determine differences in choice of exercise or sedentary behavior across the control and stress conditions, subjects chose either to exercise for progressively longer periods to earn a monetary reinforcer or to engage in a high-rated sedentary behavior., Results: The choice to exercise was influenced by stress reactivity differently in the stress and control conditions. Low heart-rate reactive children participated in similar (p > 0.50) amounts of exercise on the stress and control days, but high heart-rate reactive children participated in less (p < 0.01) exercise (22.0 +/- 2.5 vs. 26.3 +/- 2.2 minutes) on the stress than control days. When grouped by change in perceived stress, there were no group differences, but subjects exercised longer (p < 0.01) on the control day than the stress day., Discussion: Interpersonal stress decreased exercise in children susceptible to interpersonal stress. Stress-induced alterations in health behaviors may lead to weight gain in children.

Agreement between computer and questionnaire measures of delay discounting in smokers was compared. Correlations between measures for small, medium, or large rewards were significant. Log k values decreased as the reward delay increased, with values lower for the computer task than the questionnaire, with significant differences for small rewards. The 2 measures were related to smoking rate but not to age, gender, or obesity. The Bland-Altman test of agreement indicated large within-subject differences in k values between the 2 measures. The size of the difference between the log k values and magnitude of the log k values were positively related. Results suggest k values from the 2 measures are related but may not be used interchangeably.

Serum leptin concentrations and bone mass are concordant in several respects. Obesity is associated with increased serum leptin concentrations and bone mineral, whereas undernutrition reduces serum leptin concentrations and bone mineral. Furthermore, both bone mineral and serum leptin concentrations increase at the initiation of puberty. However, there is a lack of empirical evidence of an independent association of serum leptin concentrations and bone mineral in youth. Thus, we used hierarchical regression to determine whether serum leptin concentrations were related to bone mineral in boys (n = 28) and girls (n = 31). Bone mineral content, density, and apparent density of the total body and body regions were measured by dual-energy x-ray absorptiometry and statistically adjusted for chronological age, fat mass, bone-free fat-free mass, and serum IGF-I and estradiol concentrations. Sequential addition of serum log((10)) leptin concentrations to the block of body size variables and the block of hormone variables did not increase R(2) for any of the total or regional bone mineral content, bone mineral density, and bone mineral apparent density variables. We conclude that serum leptin concentrations do not add to the prediction of bone mineral in youth after accounting for age, fat mass, bone-free fat-free mass, and serum IGF-I and estradiol concentrations.

Somatic growth and maturation are influenced by a number of factors that act independently or in concert to modify an individual's genetic potential. The secular trend in height and adolescent development is further evidence for the significant influence of environmental factors on an individual's genetic potential for linear growth. Nutrition, including energy and specific nutrient intake, is a major determinant of growth. Paramount to normal growth is the general health and well-being of an individual; in fact, normal growth is a strong testament to the overall good health of a child. More recently the effect of physical activity and fitness on linear growth, especially among teenage athletes, has become a topic of interest. Puberty is a dynamic period of development marked by rapid changes in body size, shape, and composition, all of which are sexually dimorphic. One of the hallmarks of puberty is the adolescent growth spurt. Body compositional changes, including the regional distribution of body fat, are especially large during the pubertal transition and markedly sexually dimorphic. The hormonal regulation of the growth spurt and the alterations in body composition depend on the release of the gonadotropins, leptin, the sex-steroids, and growth hormone. It is very likely that interactions among these hormonal axes are more important than their main effects, and that alterations in body composition and the regional distribution of body fat actually are signals to alter the neuroendocrine and peripheral hormone axes. These processes are merely magnified during pubertal development but likely are pivotal all along the way from fetal growth to the aging process.

Objective: To determine whether dietary restraint modifies stress-induced eating in youth., Research Methods and Procedures: Snacking was measured in boys (9.5 +/- 0.3 years) and girls (9.0 +/- 0.3 years), with and without dietary restraint, across a control day after reading children's magazines and/or coloring, and on a stress day after giving a videotaped speech, with order of conditions counterbalanced. Children were divided into four groups based on dietary restraint and changes in perceived stress: low-restraint/low-reactive (n = 9), low-restraint/high-reactive (n = 13), high-restraint/low-reactive (n = 10), and high-restraint/high-reactive (n = 8). Body composition was estimated by skinfolds., Results: Energy intake of snack foods was influenced differently by dietary restraint and stress reactivity in the stress and control conditions (p < 0.01). After being stressed, low-restraint/low-reactive children ate fewer snacks and high-restraint/high-reactive children ate more snacks compared with the control condition. After covarying for percentage of body fat, the interactions remained (p < 0.01). Girls ate less than boys (p < 0.001), but sex did not influence eating in control and stress conditions., Discussion: Dietary restraint occurs in children and may influence the effect of stress on eating. Interpersonal stress decreases snacking in low dietary restrained youth but increases snacking in high dietary restrained children, perhaps because of stress-induced disinhibition.

In adults, abdominal visceral adiposity is related to an increased risk of cardiovascular diseases, Type 2 diabetes mellitus, and stroke. The antecedents of these conditions likely begin with the alterations in body fat distribution during childhood and adolescence. The sexually dimorphic alterations in fat distribution are influenced by sex differences in hormone concentrations, anatomical differences in the number and density of specific hormone receptors, capillary blood flow, and the activity of enzymes promoting lipid synthesis or degradation. Hormones influencing the amount and regional distribution of adipose tissue during puberty include cortisol, insulin, growth hormone, and the sex steroids. Cortisol and insulin promote fat deposition while the sex steroids and GH stimulate lipolysis. An overly sensitive hypothalamic-pituitary-adrenal axis may exist in obesity and disrupt the balance between the lipogenic effects of cortisol and insulin and the lipolytic effects of sex steroids and growth hormone. Leptin is released from the adipocytes and may act as a metabolic signal to the hypothalamic areas controlling satiety, energy expenditure, and the regulation of cortisol, insulin, sex steroid and growth hormone release. The complex issues of the hormonal control of alterations in body fat distribution during puberty are developed and a working model is proposed. Am. J. Hum. Biol. 11:209-224, 1999. Copyright 1999 Wiley-Liss, Inc.