Breastfeeding and growth during infancy among offspring of mothers with gestational diabetes mellitus: a prospective cohort study.

BACKGROUND: Breastfeeding (BF) may protect against obesity and type 2 diabetes mellitus in children exposed to maternal diabetes in utero, but its effects on infant growth among this high-risk group have rarely been evaluated. OBJECTIVES: The objective of this study was to evaluate BF intensity and duration in relation to infant growth from birth through 12 months among offspring of mothers with gestational diabetes mellitus (GDM). METHODS: Prospective cohort of 464 GDM mother-infant dyads (28% White, 36% Hispanic, 26% Asian, 8% Black, 2% other). Weight and length measured at birth, 6-9 weeks, 6 months and 12 months. Categorized as intensive BF or formula feeding (FF) groups at 6-9 weeks (study baseline), and intensity from birth through 12 months as Group 1: consistent exclusive/mostly FF, Group 2: transition from BF to FF within 3-9 months and Group 3: consistent exclusive/mostly BF. Multivariable mixed linear regression models estimated adjusted mean (95% confidence interval) change in z-scores; weight-for-length (WLZ), weight-for-age and length-for-age. RESULTS: Compared with intensive BF at 6-9 weeks, FF showed greater increases in WLZ-scores from 6 to 9 weeks to 6 months [+0.38 (0.13 to 0.62) vs. +0.02 (-0.15 to 0.19); p = 0.02] and birth to 12 months [+1.11 (0.87 to 1.34) vs. +0.53 (0.37 to 0.69); p < 0.001]. For 12-month intensity and duration, Groups 2 and 3 had smaller WLZ-score increases than Group 1 from 6 to 9 weeks to 6 months [-0.05 (-0.27 to 0.18) and +0.07 (-0.19 to 0.23) vs. +0.40 (0.15 to 0.64); p = 0.01 and 0.07], and birth to 12 months [+0.60 (0.39 to 0.82) and +0.59 (0.33 to 0.85) vs. +0.97 (0.75 to 1.19); p < 0.05]. CONCLUSIONS: Among offspring of mothers with GDM, high intensity BF from birth through 1 year is associated with slower infant ponderal growth and lower weight gain.

Observed parent-child feeding dynamics in relation to child body mass index and adiposity.

BACKGROUND: Restrictive feeding is associated with child overweight; however, the majority of studies used parent-report questionnaires. OBJECTIVES: The relationship between child adiposity measures and directly observed parent and child behaviours were tested using a novel behavioural coding system (BCS). METHODS: Data from 109 children, participants in a twin study and their mothers, were analyzed. Parent-child dyads were video-recorded twice in the laboratory, while children ate ad libitum from a buffet lunch. Mother and child behaviours were assessed using the BCS. Height, body weight and body fat were directly measured for each child. Associations between child adiposity measures and average BCS behaviour (i.e. pooled across visits) were tested using partial correlations adjusting for child age. RESULTS: Regarding discouragement prompts, child body mass index (BMI) z-score was significantly associated with a greater rate of total discouragements (per minute, min-1 ), nonverbal discouragements (min-1 ) and temporary (delay) discouragements (min-1 ) (p < 0.05). Child percent body fat was associated with greater nonverbal discouragements (min-1 ). Regarding encouragement prompts, child BMI z-score was significantly associated with a greater rate of total encouragements (min-1 ), nonverbal encouragements (min-1 ) and reward encouragements (min-1 ). Child BMI z-score and percent body fat were both positively associated with greater maternal health encouragements (min-1 ). Associations with encouragement to eat prompts were no longer significant when accounting for the dependence among twins (being part of the same family). CONCLUSIONS: Heavier children received greater maternal discouragements to eat and, with qualifications, encouragements to eat. The role of nonverbal parenting cues warrants further research regarding child eating regulation and obesity.

Prevention of excess weight gain in paediatric primary care: beverages only or multiple lifestyle factors. The Smart Step Study, a cluster-randomized clinical trial.

BACKGROUND: Insufficient evidence exists to support obesity prevention in paediatric primary care. OBJECTIVES: To test a theory-based behaviour modification intervention delivered by trained paediatric primary care providers for obesity prevention. METHODS: Efficacy trial with cluster randomization (practice level) and a 12-session 12-month sweetened beverages decrease intervention or a comprehensive dietary and physical activity intervention, compared with a control intervention among children ages 8-12 years. RESULTS: A low recruitment rate was observed. The increase in body mass index z-score (BMIz) for the 139 subjects (11 practices) randomized to any of the two obesity interventions (combined group) was less than that of the 33 subjects (five practices) randomized to the control intervention (-0.089, 95% confidence interval [CI]: -0.170 to -0.008, P = 0.03) with a -1.44 kg weight difference (95% CI: -2.98 to +0.10 kg, P = 0.095). The incidences of obesity and excess weight gain were lower in the obesity interventions, but the number of subjects was small. Post hoc analyses comparing the beverage only to the control intervention also showed an intervention benefit on BMIz (-0.083, 95% CI: -0.165 to -0.001, P = 0.048). CONCLUSIONS: For participating families, an obesity prevention intervention delivered by paediatric primary care clinicians, who are compensated, trained and continuously supported by behavioural specialists, can impact children's BMIz.

US pediatric population-level associations of DXA-measured percentage of body fat with four BMI metrics with cutoffs.

OBJECTIVE: Four body mass index (BMI) metrics--BMI, BMI z-score, BMI percentile and BMI%--are commonly used as proxy measures for children's adiposity. We sought to determine a BMI metric that is most strongly associated with measured percentage of body fat (%BF) in the US pediatric population stratified by sex, age and race/ethnicity, and to determine cutoffs that maximize the association for each BMI metric. SUBJECTS, DESIGN AND METHODS: %BF was measured by dual-energy X-ray absorptiometry among N=6120 US boys and girls aged 8.0-17.9 years old from the National Health and Nutrition Examination Survey 1999-2004. We fit piecewise linear regression models with cutoffs to %BF data using each BMI metric as the predictor stratified by sex, race/ethnicity and age. The slopes were modeled differently before and after the cutoffs which were determined on the basis of grid searches. RESULTS: BMI z-score was in general most strongly associated with %BF for both boys and girls. The associations of the four BMI metrics were lowest for boys aged 12-13.9 years and girls aged 16-17.9 years, and strongest for Mexican-American boys and for non-Hispanic Black girls. Overall, the associations were stronger for girls than for boys. In boys, BMI had the lowest association with %BF (R(2)=0.39) for all ages combined. The fold changes in slopes before and after cutoffs were greatest in general for BMI percentiles regardless of age, sex and race/ethnicity. BMI z-score cutoffs were 0.4 for both boys and girls for all ages combined. Except for BMI, the slopes after the cutoffs were in general greater than those before. CONCLUSIONS: All BMI metrics were strongly associated with %BF when stratified by age and race/ethnicity except that BMI was the least associated with %BF in boys for all ages combined. Overall, BMI z-score was superior for evaluation of %BF, and its cutoff of 0.4 can also serve as a threshold for careful monitoring of weight status.

Effects of providing personalized feedback of child's obesity risk on mothers' food choices using a virtual reality buffet.

BACKGROUND: Providing personalized genetic-risk feedback of a child's susceptibility to adult-onset health conditions is a topic of considerable debate. Family health history (FHH), specifically parental overweight/obesity status, is a useful assessment for evaluating a child's genetic and environmental risk of becoming obese. It is unclear whether such risk information may influence parents' efforts to reduce their child's risk of obesity. PURPOSE: To evaluate whether telling mothers the magnitude of their child's risk of becoming obese based on personal FHH influenced food choices for their young child from a virtual reality-based buffet restaurant. METHODS: Overweight/obese mothers of a child aged 4-5 years who met eligibility criteria (N=221) were randomly assigned to one of three experimental arms, which emphasized different health information: arm 1, food safety control (Control); arm 2, behavioral-risk information (BRI) alone or arm 3, behavioral-risk information plus personal FHH-based risk assessment (BRI+FHH). Mothers donned a head-mounted display to be immersed in a virtual restaurant buffet, where they selected virtual food and beverages as a lunch for their child. RESULTS: Mothers who were randomized to BRI+FHH filled the index child's plate with an average of 45 fewer calories than those in the Control arm (P<0.05); those in the BRI arm filled the plate with 35 fewer calories than the Control arm, a non-significant difference. Calorie restriction was greatest among mothers in the BRI+FHH arm who received the weaker-risk message (that is, only one overweight parent). CONCLUSIONS: The influence of communicating a child's inherited risk of obesity on mothers' feeding practices may vary by the risk level conveyed. High-risk messages may best be coupled with strategies to increase mother's perceptions that efforts can be undertaken to reduce risk and build requisite behavioral skills to reduce risk.

A twin study of self-regulatory eating in early childhood: estimates of genetic and environmental influence, and measurement considerations.

OBJECTIVE: Children differ greatly in their ability to self-regulate food intake for reasons that are poorly understood. This laboratory-based twin study tested the genetic and environmental contributions to self-regulatory eating and body fat in early childhood. METHODS: A total of 69 4-7 year-old same-sex twin pairs, including 40 monozygotic and 29 dizygotic pairs, were studied. Self-regulatory eating was operationalized as the percentage compensation index (COMPX%), assessed by a 'preload' challenge in which lunch intake was measured following a low- (3 kcal) or high-calorie (159 kcal) drink. Body fat indexes also were measured. The familial association for COMPX% was estimated by an intraclass correlation, and biometric analyses estimated heritability. RESULTS: Children ate more at lunch following the low- compared with high-energy preload (P<0.001), although variability in COMPX% was considerable. Compensation was significantly poorer among African American and Hispanic compared with European American children, and among girls compared with boys. There was a familial association for self-regulatory eating (ρ = 0.23, P = 0.03) but no significant genetic component. In all, 22% of the variance in COMPX% was due to shared environmental 'household' factors, with the remaining variance attributable to child-specific 'unique' or 'random' environments. Poorer self-regulatory eating was associated with greater percent body fat (r = -0.21, P = 0.04). CONCLUSIONS: Self-regulatory eating was influenced by environmental factors, especially those differing among siblings. The absence of a significant genetic effect may reflect the age of the sample or could be artifactual due to measurement issues that need to be considered in future studies.

Evidence for prospective associations among depression and obesity in population-based studies.

Obesity may lead to depression or be one of its consequences. We reviewed population-based studies in order to, first, identify the most commonly used research methods, and, second, to evaluate the strength of evidence for prospective associations among obesity and depression. We examined 25 studies, of which 10 tested 'obesity-to-depression' pathways, and 15 tested 'depression-to-obesity' pathways. Descriptive statistics summarized the frequency with which various measurements, designs and data analytic strategies were used. We tallied the number of studies that reported any vs. no statistically significant associations, and report on effect sizes, identified moderating variables within reports, and sought common findings across studies. Results indicated considerable methodological heterogeneity in the literature. Depression was assessed by clinical interview in 44% of studies, weight and height were directly measured in 32%, and only 12% used both. In total, 80% of the studies reported significant obesity-to-depression associations, with odds ratios generally in the range of 1.0 to 2.0, while only 53% of the studies reported significant depression-to-obesity associations. Sex was a common moderating variable. Thus, there was good evidence that obesity is prospectively associated with increased depression, with less consistent evidence that depression leads to obesity. Recommendations for future research regarding study samples, measurement and data analysis are provided.

Intentional weight loss and changes in symptoms of depression: a systematic review and meta-analysis.

OBJECTIVE: Obesity is related to increased risk of several health complications, including depression. Many studies have reported improvements in mood with weight loss, but results have been equivocal. The present meta-analysis examined changes in symptoms of depression that were reported in trials of weight loss interventions. Between-groups comparisons of different weight loss methods (for example, lifestyle modification, diet-alone and pharmacotherapy) were examined, as were within-group changes for each treatment type. METHOD: MEDLINE was searched for articles published between 1950 and January 2009. Several obesity-related terms were intersected with terms related to depression. Results were filtered to return only studies of human subjects, published in English. Of 5971 articles, 394 were randomized controlled trials. Articles were excluded if they did not report mean changes in weight or symptoms of depression, included children or persons with psychiatric disorders (other than depression), or provided insufficient data for analysis. Thirty-one studies (n=7937) were included. Two authors independently extracted a description of each study treatment, sample characteristics, assessment methods and changes in weight and symptoms of depression. Treatments were categorized as lifestyle modification, non-dieting, dietary counseling, diet-alone, exercise-alone, pharmacotherapy, placebo or control interventions. RESULTS: Random effects models found that lifestyle modification was superior to control and non-dieting interventions for reducing symptoms of depression, and marginally better than dietary counseling and exercise-alone programs. Exercise-alone programs were superior to controls. No differences were found for comparisons of pharmacologic agents and placebos. Within-group analyses found significant reductions in symptoms of depression for nearly all active interventions. A meta-regression found no relationship between changes in weight and changes in symptoms of depression in lifestyle modification interventions. CONCLUSIONS: On average, obese individuals in weight loss trials experienced reductions in symptoms of depression. Future studies should examine incidence and resolution of clinically significant depressive disorders with weight loss interventions.

Infant temperament and eating style predict change in standardized weight status and obesity risk at 6 years of age.

OBJECTIVE: Little research has addressed the relationships among infant temperament, eating styles and obesity risk. To address this gap, we tested whether infant temperament and eating patterns at the age of 1 year are associated with a greater increase in standardized weight status, and greater obesity risk at 6 years of age. DESIGN: A secondary, prospective analysis of the Colorado Adoption Study was conducted. The main predictor variables were infant temperament (that is, emotionality, activity, attention span-persistence, reaction to food and soothability) and eating domains (that is, reactivity to food, predictable appetite and distractability at mealtime) at the age of 1 year, along with the body mass index (BMI) of biological mothers. The outcome measures were child weight and height (length) assessed at ages 1 through 6 years, from which weight-for-length and BMI were computed along with the standardized indexes (z-scores) and percentiles. Overweight/obesity status was computed at each year as well. PARTICIPANTS: A primarily White sample of 262 boys and 225 girls, assessed at ages 1 through 6 years, along with their mothers. RESULTS: Among boys, greater attention span-persistence was associated with reduced standardized weight status gain (ß=-0.15, P<0.05) and reduced obesity risk (odds ratio (OR)=0.46, P=0.06). Among girls, greater soothability and negative reaction to food were associated with greater standardized weight status gain (ß=0.19, P<0.01; and ß=0.16, P<0.05, respectively) and increased obesity risk (OR=3.72, P=0.03; and OR=2.81, P=0.08, respectively). Biological mothers' obesity status predicted obesity risk in boys (OR=3.07, P=0.01) and girls (OR=5.94, P=0.03). CONCLUSIONS: Male infants with less attention span, and female infants with greater soothability or a more negative food reaction, showed greater increases in standardized weight and were more likely to be overweight/obese at the age of 6 years. The role of infant temperament in pediatric obesity onset warrants greater research.

Rationale, design and methods of the HEALTHY study behavior intervention component.

HEALTHY was a multi-center primary prevention trial designed to reduce risk factors for type 2 diabetes in adolescents. Seven centers each recruited six middle schools that were randomized to either intervention or control. The HEALTHY intervention integrated multiple components in nutrition, physical education, behavior change and communications and promotion. The conceptual rationale as well as the design and development of the behavior intervention component are described. Pilot study data informed the development of the behavior intervention component. Principles of social learning and health-related behavior change were incorporated. One element of the behavior intervention component was a sequence of peer-led, teacher-facilitated learning activities known as FLASH (Fun Learning Activities for Student Health). Five FLASH modules were implemented over five semesters of the HEALTHY study, with the first module delivered in the second semester of the sixth grade and the last module in the second semester of the eighth grade. Each module contained sessions that were designed to be delivered on a weekly basis to foster self-awareness, knowledge, decision-making skills and peer involvement for health behavior change. FLASH behavioral practice incorporated individual and group self-monitoring challenges for eating and activity. Another element of the behavior intervention component was the family outreach strategy for extending changes in physical activity and healthy eating beyond the school day and for supporting the student's lifestyle change choices. Family outreach strategies included the delivery of newsletters and supplemental packages with materials to promote healthy behavior in the home environment during school summer and winter holiday breaks. In conclusion, the HEALTHY behavior intervention component, when integrated with total school food and physical education environmental changes enhanced by communications and promotional campaigns, is a feasible and acceptable mechanism for delivering age-appropriate social learning for healthy eating and physical activity among an ethnically diverse group of middle school students across the United States.

Dietary energy density increases during early childhood irrespective of familial predisposition to obesity: results from a prospective cohort study.

OBJECTIVE: This study compared 4-year changes in daily energy density (ED; kcal/g) in children born at different risk for obesity, characterized the stability of ED and examined associations between ED and child body composition. DESIGN: Prospective cohort study to measure habitual dietary ED of children who are born at different risk for obesity. SUBJECTS: Children who were born at high risk (n=22) or low risk (n=27) for obesity based on maternal pre-pregnancy weight. MEASUREMENTS: Three-day food records were collected from children's mothers at child ages 3, 4, 5 and 6 years. Three categories of ED were computed (food only, food and milk, and food and all beverages) and body composition assessed at each year. RESULTS: The mean (+/-s.e.m.) ED increased over time across all children (linear trend: P<0.003): 2.18+/-0.07 to 2.32+/-0.06 kcal/g (food only); 1.66+/-0.07 to 1.82+/-0.06 kcal/g (food and milk); and 1.24+/-0.04 to 1.37+/-0.05 kcal/g (food and all beverages). Intraindividual coefficients of variation were smaller than those previously reported for adults. Weight indices were not correlated with dietary ED (P>0.05). CONCLUSION: Dietary ED increased in young children, irrespective of their predisposition to obesity, between the ages of 3 and 6 years. The genes that promote childhood obesity may not exert their influence through dietary ED, which may be more strongly influenced by environmental factors.

Co-twin control designs for testing behavioral economic theories of child nutrition: methodological note.

OBJECTIVE: To illustrate the use and potential efficiency of the co-twin control design for testing behavioral economic theories of child nutrition. DESIGN: Co-twin control design, in which participating twins ate an ad libitum lunch on two laboratory visits. At visit 1, child food choices were not reinforced. On visit 2, twins were randomized to conditions such that one twin was reinforced for each fruit and vegetable serving consumed during lunch ('contingent') while his co-twin was reinforced irrespective of food intake ('non-contingent'). SUBJECTS: Six male twins, 5 years old, from three monozygotic twin pairs. MEASUREMENTS: Ad libitum intake of total energy (kcals), fat (kcals), and fruits and vegetables (servings) from the protocol test meals on the two visits. RESULTS: Compared to twins receiving non-contingent reinforcement, twins receiving contingent reinforcement increased fruit and vegetable intake by 2.0 servings, reduced fat intake 106.3 kcals, and reduced total energy intake by 112.7 kcals. The relative efficiency of the co-twin control design compared to a conventional between-groups design of unrelated children was most powerful for detecting 'substitution effects' (i.e., reduced total energy and fat intake) more so than for detecting increased fruit and vegetable intake. CONCLUSION: Genetically informative studies, including the co-twin control design, can provide conceptually elegant and efficient strategies for testing environmental theories of child nutrition and obesity.

Maternal restriction of children's eating and encouragements to eat as the 'non-shared environment': a pilot study using the child feeding questionnaire.

OBJECTIVE: This pilot study tested whether maternal feeding attitudes and styles towards children are part of the 'shared' or 'non-shared' home environment. A secondary aim was to test whether within-family differences in maternal feeding attitudes and styles relate to within-family differences in child weight status. METHODS: Mothers of 3- to 7-year-old sibling pairs (N=15 pairs) completed the Child Feeding Questionnaire (CFQ), which assessed feeding attitudes (perceived responsibility, perceived child overweight and child weight concern) and feeding styles (monitoring, restriction and pressure to eat) towards children. Mothers rated each sibling separately. Child weight and height were measured and converted to body mass index (BMI) z-scores. Intraclass correlations tested the familial associations for each CFQ subscale. Pearson's correlations tested whether within-family differences in CFQ subscales were related to within-family differences in child BMI z-scores. RESULTS: Perceived responsibility (rho=0.77, P=0.0004), perceived child overweight (rho=0.99, P<0.0001) and monitoring (rho=0.57, P=0.01) showed significant familial correlations. Mothers reported significantly greater weight concern (r=0.85, P=0.02) and reduced pressure to eat (r=-0.80, P=0.03) towards heavier than thinner children within families. CONCLUSION: Whether or not maternal feeding practices are shared or non-shared components of the home environment depends on the specific feeding domain being measured. Restrictive feeding practices and encouragements to eat by mothers might be tested as non-shared environmental variables in genetics studies of childhood obesity.

'Take the stairs instead of the escalator': effect of environmental prompts on community stair use and implications for a national 'Small Steps' campaign.

The US government initiated a national health campaign targeting 100 'small step' lifestyle changes to combat obesity. Small Step #67 advocates stair instead of escalator usage in public settings. The aim of this study is to evaluate the effects of motivational signs prompting stair use over escalator use on pedestrians' stair usage in commuter settings. Eight studies, testing the effects of motivational prompts on stair vs. escalator usage in public settings, were reviewed. Participant and study attributes were descriptively coded. Effect size was calculated as the change in percent units of stair users during the intervention phases vs. the baseline phase. The average study included approximately 45,000 observations that were recorded across an average of 15 weeks of intervention. The mean +/- SD change in percent units of stair users was 2.8% +/- 2.4% (P < 0.001), and effects were twice as large in females (4.8%) as in males (2.4%). The number of stairs/building, baseline stair use, and total intervention weeks predicted change in stair use, although the effects were clinically miniscule. In a hypothetical city intervention, we projected that a 2.8% increase in stair usage would result in a weight loss and/or weight gain prevention of 300 g/person/year among new stair users. In sum, point-of-decision motivational signs may help communities attain Small Step #67. However, the singular impact of this community intervention on correcting energy imbalance may be minimal, having slight impact itself on reducing the national obesity prevalence.

Depressive mood and obesity in US adults: comparison and moderation by sex, age, and race.

OBJECTIVE: Sustained depressive mood is a gateway symptom for a major depressive disorder. This paper investigated whether the association between depressive mood and obesity differs as function of sex, age, and race in US adults after controlling for socio-economic variables of martial status, employment status, income level and education level. METHODS: A total of 44,800 nationally representative respondents from the 2001 Behavioral Risk Factor Surveillance Survey were studied. Respondents were classified as having experienced a depressive mood if they felt sad, blue, or depressed at least for 1 week in the previous month. The depressive mood was operationalized in terms of duration and sustenance, both defined based on number of days with depressive mood: 7+ and 14+ days. Age groups were classified as young (18-64 years) and old (65+ years). Obesity status was classified as: not overweight/obese (BMI<25); overweight (25or=30). RESULTS: Prevalence of prior-month depressive mood was 14.3 and 7.8% for 7+ and 14+ days, respectively. Controlling for race and socio-economic variables, both young overweight and obese women were significantly more likely to have experienced depressive mood than nonoverweight/nonobese women. Young overweight, but not obese, men were significantly more likely to have experienced depressive mood than nonoverweight/nonobese men. Young obese women were also significantly more likely to have a sustained depressive mood than nonoverweight/nonobese women. For old respondents, depressive mood and its sustenance were not associated with obesity in either sex. DISCUSSION: The relationship between the depressive mood and obesity is dependent upon gender, age, and race. Young obese women, Hispanics in particular, are much more prone to depressive mood than nonobese women. Future studies testing associations between depression and obesity should be sensitive to the influence of these demographic and socio-economic variables.

Development and modification of child food preferences and eating patterns: behavior genetics strategies.

Behavioral genetics (BG) designs can offer useful strategies for studying the development of child food preferences and eating patterns. This review summarizes BG designs that tested familial influences on child eating behavior and implicated both genetic and home environmental factors. A range of BG strategies, including family and pseudo-family designs, classic twins designs, discordant sibling designs, cotwin control designs, and high-risk designs, have provided information on child development that could not have been obtained from the analysis of singletons. BG designs can provide can powerful tools for testing environmental theories of child nutrition and, potentially, for better understanding between-child variability in response to dietary interventions for overweight. The term BG may misleadingly imply only the classic twin design or just heritability estimation; BG strategies can be adapted creatively to address a range of questions concerning the development of child appetite and eating regulation.

What is the best measure of adiposity change in growing children: BMI, BMI %, BMI z-score or BMI centile?

BACKGROUND: Weight control programs for obese children monitor change in body mass index (BMI) adjusted for age. However, change can be measured in several ways: raw (kg/m2) units, percentage, z-scores or centiles. The suitability of the different measures is not known. AIM: To identify the optimal BMI measure for change, whose short-term variability is most consistent for children across the spectrum of adiposity. SETTING: An Italian kindergarten. SUBJECTS: A total of 135 (66 female) children aged 29-68 months at baseline, with BMI measured three times over a 9-month period. METHODS: Each child's short-term variability in adiposity was summarized by the standard deviation (s.d.) of BMI and BMI % adjusted for age, and BMI z-score and BMI centile. The s.d.'s were then compared in obese and nonobese children, and also correlated with each child's baseline BMI z-score. RESULTS: The within-child s.d.s of BMI z-score and BMI centile were significantly smaller in obese than nonobese children, while the s.d.s of BMI and BMI % were similar in the two groups. Also, the within-child s.d.s of z-score and centile, and to a lesser extent BMI %, were significantly inversely correlated with baseline z-score, whereas the s.d. of BMI was not. The changes in adiposity over time, as assessed by the four measures, were very highly correlated with each other, particularly for BMI with BMI %. DISCUSSION: Even though BMI z-score is optimal for assessing adiposity on a single occasion, it is not necessarily the best scale for measuring change in adiposity, as the within-child variability over time depends on the child's level of adiposity. Better alternatives are BMI itself or BMI %. Our results underscore the importance of using a relatively stable method to assess adiposity change when following children at risk of obesity.

Genetics of food intake and body composition: lessons from twin studies.

Twin studies are useful designs for decomposing genetic and environmental influences on traits, with the basic goal being to map variations in phenotypic similarity onto variances in genetic similarity. In this review, we provide an overview of twin studies that have been used to decompose the genetic and environmental influences behind body composition, eating style, and their covariation. Although many published reports have established that genes contribute anywhere from 50-90% of the variance in body mass index (BMI, kg/m(2)), fewer studies have used laboratory- based body composition measures. Moreover, comparable studies of human eating style are even more scarce. Advances in the laboratory measurement of human eating behavior may increase the yield of twin studies that solely focus on body composition.

Pediatric body composition in clinical studies: which methods in which situations?

There is currently much interest in the subject of pediatric obesity. Accurate measures of body composition are required given the potential influence of variables such as growth, metabolic rate, physical activity, and physical fitness. Because boys and girls have a different growth pattern, gender is a fundamental consideration when measuring children and assessing body composition. The central aim of this paper is to review methods of pediatric body composition assessment that can provide new insights for clinical practice.