Sue Y. S. Kimm

Childhood Obesity – 2010: Progress and Challenges

Worldwide prevalence of childhood obesity has increased greatly during the past three decades. The increasing occurrence in children of disorders such as type 2 diabetes is believed to be a consequence of this obesity epidemic. Much progress has been made in understanding of the genetics and physiology of appetite control and from these advances, elucidation of the causes of some rare obesity syndromes. However, these rare disorders have so far taught us few lessons about prevention or reversal of obesity in most children. Calorie intake and activity recommendations need reassessment and improved quantification at a population level because of sedentary lifestyles of children nowadays. For individual treatment, currently recommended calorie prescriptions might be too conservative in view of evolving insight into the so-called energy gap. Although quality of research into both prevention and treatment has improved, high-quality multicentre trials with long-term follow-up are needed. Meanwhile, prevention and treatment approaches to increase energy expenditure and decrease intake should continue. Recent data suggest that the spiralling increase in childhood obesity prevalence might be abating; increased efforts should be made on all fronts to continue this potentially exciting trend.

Relation between the changes in physical activity and body-mass index during adolescence : a multicentre longitudinal study

BACKGROUNDnThe role of physical activity in preventing obesity during adolescence remains unknown. We examined changes in activity in relation to changes in body-mass index (BMI) and adiposity in a cohort of 1152 black and 1135 white girls from the USA, who were followed up prospectively from ages 9 or 10 to 18 or 19 years.nnnMETHODSnBMI and sum of skinfold thickness were assessed annually, whereas habitual activity was assessed at years 1 (baseline), 3, 5, and 7-10. Each girls overall activity status was categorised as active, moderately active, or inactive. Longitudinal regression models examined associations between changes in activity and in overall activity status with changes in BMI and in sum of skinfold thickness.nnnFINDINGSnEach decline in activity of 10 metabolic equivalent [MET]-times per week was associated with an increase in BMI of 0.14 kg/m2 (SE 0.03) and in sum of skinfold thickness of 0.62 mm (0.17) for black girls, and of 0.09 kg/m2 (0.02) and 0.63 mm (0.13) for white girls. At ages 18 or 19 years, BMI differences between active and inactive girls were 2.98 kg/m2 (p<0.0001) for black girls and 2.10 kg/m2 (p<0.0001) for white girls. Similar results were apparent for sum of skinfold thickness. For moderately active girls, changes in BMI and sum of skinfold thickness were about midway between those for active and inactive girls.nnnINTERPRETATIONnChanges in activity levels of US girls during adolescence significantly affected changes in BMI and adiposity. Thus, preventing the steep decline in activity during adolescence is an important method to reduce obesity.

Longitudinal changes in physical activity in a biracial cohort during adolescence

PURPOSEnThis report describes the development and use of two self-report methods and an objective measure to assess longitudinal changes in physical activity in a large biethnic cohort of young girls from childhood through adolescence.nnnMETHODSnThe NHLBI Growth and Health Study (NGHS) is a multicenter study of obesity development in 2379 black and white girls followed from ages 9-10 yr to 18-19 yr (NGHS years 1-10). A Caltrac activity monitor was used to objectively quantify activity levels in years 3-5. A 3-d diary (AD) and a habitual patterns questionnaire (HAQ) were administered annually and biannually, respectively, to subjectively quantify physical activity levels. The changing pattern of activities as the girls matured during the 10-yr study period necessitated periodic form changes. Empirical analytic approaches were developed to help distinguish between true longitudinal changes in activity levels from potential numerical artifacts resulting from modifications in forms.nnnRESULTSnThe longitudinal activity data indicate a steep decline in the level of reported activity from baseline to year 10 as indicated by AD scores (446.8 to 292.1 MET-min x d(-1), 35%) as well as by HAQ scores (29.3 to 4.9 MET-times x wk(-1), 83%). This parallel trend in the pattern of the decline in activity among the two self-report methods was mirrored by a similar decline using the Caltrac method of physical activity assessment. From years 3 to 5, the AD decreased by 22%, whereas both the HAQ and Caltrac declined by 21%.nnnCONCLUSIONnThe longitudinal data on physical activity collected in the NGHS cohort further confirm a dramatic decrease in the overall level of physical activity during the transition from childhood to adolescence. The consistency among the three methods indicate that both the AD and HAQ are useful tools for the assessment of activity levels in adolescent girls.

Race, socioeconomic status, and obesity in 9- to 10-year-old girls: The NHLBI growth and health study

The purpose of this investigation was to determine whether measures of socioeconomic status (SES) are inversely associated with obesity in 9- to 10-year-old black and white girls and their parents. Subjects were participants in the Growth and Health Study (NGHS) of the National Heart, Lung, and Blood Institute. Extensive SES, anthropometric, and dietary data were collected at baseline on 2379 NGHS participants. The prevalence of obesity was examined in the NGHS girls and parents in relation to SES and selected environmental factors. Less obesity was observed at higher levels of household income and parental education in white girls but not in black girls. Among the mothers of the NGHS participants who were seen, lower prevalence of obesity was observed with higher levels of income and education for white mothers, but no consistent patterns were seen in black mothers. Univariate logistic models indicated that the prevalence of obesity was significantly and inversely associated with parental income and education and number of parents in the household in white girls whereas caloric intake and TV viewing were significantly and positively associated with obesity. Among black girls, only TV viewing was significantly and positively associated with the prevalence of obesity. Multivariate logistic regression models revealed that lower parental educational attainment, one-parent household, and increased caloric intake were significantly associated with the prevalence of obesity in white girls; for black girls, only increased hours of TV viewing were significant in these models. It is concluded that socioeconomic status, as measured by education and income, was related to the prevalence of obesity in girls, with racial variation in these associations. A lower prevalence of obesity was seen at higher levels of socioeconomic status in white girls, whereas no clear relationship was detected in black girls. These findings raise new questions regarding the correlates of obesity in black girls.

Nutrient Intake and Blood Pressure in the Dietary Intervention Study in Children

Delineating the role that diet plays in blood pressure levels in children is important for guiding dietary recommendations for the prevention of hypertension. The purpose of this study was to investigate relationships between dietary nutrients and blood pressure in children. Data were analyzed from 662 participants in the Dietary Intervention Study in Children who had elevated low-density lipoprotein cholesterol and were aged 8 to 11 years at baseline. Three 24-hour dietary recalls, systolic pressure, diastolic pressure, height, and weight were obtained at baseline, 1 year, and 3 years. Nutrients analyzed were the micronutrients calcium, magnesium, and potassium; the macronutrients protein, carbohydrates, total fat, saturated fat, polyunsaturated fat, and monounsaturated fat; dietary cholesterol; and total dietary fiber. Baseline and 3-year longitudinal relationships were examined through multivariate models on diastolic and systolic pressures separately, controlling for height, weight, sex, and total caloric intake. The following associations were found in longitudinal analyses: analyzing each nutrient separately, for systolic pressure, inverse associations with calcium (P < .05); magnesium, potassium, and protein (all P < .01); and fiber (P < .05), and direct associations with total fat and monounsaturated fat (both P < .05); for diastolic pressure, inverse associations with calcium (P < .01); magnesium and potassium (both P < .05), protein (P < .01); and carbohydrates and fiber (both P < .05), and direct associations with polyunsaturated fat (P < .01) and monounsaturated fat (P < .05). Analyzing all nutrients simultaneously, for systolic pressure, direct association with total fat (P < .01); for diastolic pressure, inverse associations with calcium (P < .01) and fiber (P < .05), and direct association with total and monounsaturated fats (both P < .05). Results from this sample of children with elevated low-density lipoprotein cholesterol indicate that dietary calcium, fiber, and fat may be important determinants of blood pressure level in children.

The dietary intervention study in children (DISC) : dietary assessment methods for 8- to 10-year-olds

OBJECTIVESnThe dietary assessment methods used in the Dietary Intervention Study in Children (DISC) are described and the rationale, validity, and/or general usefulness of each are discussed.nnnDESIGNnDISC is the first multicenter, randomized, clinical trial to study the feasibility and long-term efficacy, safety, and acceptability of a fat-moderately diet in 8- to 10-year-old prepubescent children with moderately elevated plasma low-density lipoprotein cholesterol (LDL-C) levels. Final data collection for the original study (DISC I) occurred December 1, 1993; continued intervention and follow-up (DISC II) will extend beyond 1997.nnnSETTINGnSix clinical centers across the country participate in DISC.nnnSUBJECTSnPreadolescent boys and girls with fasting LDL-C levels between the 80th and 98th age-specific and sex-specific percentiles established by the Lipid Research Clinics were eligible for the study. The feasibility phase included 140 children who were then enveloped into the full-scale trial. Baseline dietary data for 652 randomized children in the full-scale trial and 6-month results for the feasibility cohort are reported.nnnINTERVENTIONSnDietary assessment involved several elements: (a) determining eligibility based on consumption of more than 30% of energy from total fat, (b) monitoring adherence to and adequacy of the intervention diet, (c) evaluating acceptability of the diet in the intervention group, and (d) determining appropriate foods for the intervention diet. Methods are described for each purpose.nnnMAIN OUTCOME MEASURESnLDL-C differences between the two groups and differences in total and saturated fat intakes as calculated from three 24-hour recalls were the primary outcome measures. Six-month dietary differences in the feasibility group are reported.nnnSTATISTICAL METHODSnBaseline group means and 6-month differences in dietary intake are reported for the full-scale trial and feasibility study, respectively.nnnRESULTSnBaseline mean intake from three dietary recalls for the intervention (n = 328) and control (n = 324) groups, respectively, were as follows: energy = 1,759 kcal and 1,728 kcal; total energy from fat = 33.3% and 34.0%; total energy from saturated fat = 12.5% and 12.7%; and total dietary cholesterol = 209 mg and 195 mg. After 6 months of intervention, percentage of energy from total fat and saturated fat was reduced by 5.1% (P = .004) and 2.9% (P < .001), respectively, in this feasibility subset (n = 73) of the intervention group. Essentially no change in these parameters occurred in the control group (n = 67), which demonstrates a measurable difference in reporting between groups.nnnAPPLICATIONS/CONCLUSIONSnResults illustrate the feasibility of implementing a variety of dietary assessment methods among preadolescent children without relying primarily on parental reports.

Higher Self-reported Physical Activity Is Associated With Lower Systolic Blood Pressure: The Dietary Intervention Study in Childhood (DISC)

OBJECTIVE. Children participating in a dietary clinical trial were studied to (1) assess physical activity patterns in boys and girls longitudinally from late childhood through puberty and (2) determine the association of level of physical activity on systolic blood pressure, low-density lipoprotein cholesterol, and BMI. PATIENTS AND METHODS. In the Dietary Intervention Study in Childhood, a randomized clinical trial of a reduced saturated fat and cholesterol diet in 8- to 10-year-olds with elevated low-density lipoprotein, a questionnaire that determined time spent in 5 intensity levels of physical activity was completed at baseline and at 1 and 3 years. An estimated-metabolic-equivalent score was calculated for weekly activity; hours per week were calculated for intense activities. We hypothesized that weekly self-reported physical activity would be associated with lower systolic blood pressure, low-density lipoprotein, and BMI over 3 years. Longitudinal data analyses were performed for each outcome (systolic blood pressure, low-density lipoprotein, and BMI) by using generalized estimating equations with estimated-metabolic-equivalent score per week as the independent variable adjusted for visit, gender, and Tanner stage (BMI was included in models for systolic blood pressure and low-density lipoprotein). RESULTS. The initial study cohort comprised 663 youths (362 boys [mean age: 9.7 years] and 301 girls [mean age: 9.0 years), of whom 623 (94%) completed the 3-year visit. For every 100 estimated-metabolic-equivalent hours of physical activity, there was a decrease of 1.15 mmHg of systolic blood pressure. There was a 1.28 mg/dL decline in low-density lipoprotein for a similar energy expenditure. For BMI, an analysis of intense physical activity showed that for every 10 hours of intense activity, there was a trend toward significance with a 0.2 kg/m2 decrease. CONCLUSIONS. Children with elevated cholesterol levels who lead a more physically active lifestyle have lower systolic blood pressure and a trend toward lower low-density lipoprotein over a 3-year interval. Long-term participation in intense physical activity may reduce BMI as well.

Dietary patterns of U.S. children: Implications for disease prevention☆

Nutritional data from the second National Health and Nutrition Examination Survey (NHANES II) were analyzed to assess dietary patterns of a representative sample of U.S. children and youth ages 1-17 years. The data show that the average U.S. childs diet is relatively high in total and saturated fat and low in the ratio of polyunsaturated to saturated fat. These dietary patterns deviate from current dietary recommendations for the prevention of cardiovascular diseases. The percentage contributions of specific macronutrients to total energy intake (in kilocalories) were total fat, 35-36%; total carbohydrates, 49-51%; and protein, 15-16%. This is in contrast to current expert recommendations for children of 30% of kilocalories as total fat, 55% as carbohydrates, and 15% as protein. The observed intake of saturated fat in U.S. children was 13% of kilocalories vs a recommended level of 10% of kilocalories. The observed ratio of polyunsaturated to saturated fat intake was 0.4 vs a recommended ratio of 1.0. There were important racial differences in fat intakes, with blacks generally having higher cholesterol and total fat intakes. White children generally consumed more of their calories as carbohydrates than did black children, but there were no differences in protein intakes between the two groups. In summary, these data suggest that the average U.S. childs diet deviates from recommended dietary guidelines for fat and cholesterol intakes. Black childrens dietary patterns appear less favorable for cardiovascular health than those of white children. However, the data also show that achieving recommended dietary intake patterns probably will not require drastic changes in the U.S. childs diet.

Self-esteem and adiposity in black and white girls: the NHLBI Growth and Health Study

PURPOSEnObesity is assumed to have a negative impact on self-esteem because of the associated social stigmatization in Western society. Studies of the psychological effect of obesity in children are inconclusive and limited, particularly pertaining to minority populations. Most studies have assessed global rather than domain-specific measures of self-esteem and hence, may have lacked specificity to detect impairment of certain aspects of self-esteem most closely associated with obesity. The purpose of this study is to examine the effect of adiposity and other environmental factors on measures of perceived competence and self-adequacy in 2205 black and white girls aged 9-10 years.nnnMETHODSnDomain-specific measures of self-esteem were studied by race and degree of adiposity, using Harters Self-Perception Profile for Children. Three Harter scales deemed more relevant to obesity (social acceptance (SA), physical appearance (PA), and global self-worth (GSW)) were selected for univariate and multivariate linear regression models to examine relationships between self-esteem level and adiposity (measured by the sum of triceps, subscapular, and suprailiac skinfolds (SSF)), race, pubertal maturation, and parental education. The relationship between adiposity and Harter scores was further examined with LOESS curves and also by comparing the mean scores of each quintile of SSF by race, as well as inter-quintile differences within race.nnnRESULTSnAdiposity in general impacted negatively on the scores of all three selected Harter scales. There was also racial variation in the relationship between the scores and adiposity, with the magnitude of the effect somewhat less in black girls. White girls exhibited a significant inverse relationship between SSF and SA scores while, in striking contrast, there was no variation in scores in black girls across all ranges of adiposity. Although there was a significant inverse relationship between adiposity and PA and GSW in both groups, the slope was steeper in white girls, particularly at higher ranges of SSF. Non-linearity in the relationship between SSF and the scores was seen in SA and PA scales.nnnCONCLUSIONSnThe present study demonstrated a significant negative association between adiposity and the level of self-esteem in girls as young as 9 to 10 years. There were also intriguing racial differences in the selected domains of esteem. These results may help better understand cultural differences regarding the psychological impact of obesity and could be used to formulate appropriate strategies for public health policy.

Effects of Diet and Sexual Maturation on Low-Density Lipoprotein Cholesterol During Puberty The Dietary Intervention Study in Children (DISC)

BACKGROUNDnThe Dietary Intervention Study in Children (DISC) is a multicenter, randomized, controlled clinical trial designed to examine the efficacy and safety of a dietary intervention to reduce serum LDL cholesterol (LDL-C) in children with elevated LDL-C.nnnMETHODS AND RESULTSnThe effects of dietary intake of fat and cholesterol and of sexual maturation and body mass index (BMI) on LDL-C were examined in a 3-year longitudinal study of 663 boys and girls (age 8 to 10 years at baseline) with elevated LDL-C levels. Multiple linear regression was used to predict LDL-C at 3 years. For boys, LDL-C decreased by 0.018 mmol/L for each 10 mg/4.2 MJ decrease in dietary cholesterol (P<.05). For girls, no single nutrient was significant in the model, but a treatment group effect was evident (P<.05). In both sexes, BMI at 3 years and LDL-C at baseline were significant and positive predictors of LDL-C levels. In boys, the average LDL-C level was 0.603 mmol/L lower at Tanner stage 4+ than at Tanner stage 1 (P<.01). In girls, the average LDL-C level was 0.274 mmol/L lower at Tanner stage 4+ than at Tanner stage 1 (P<.05).nnnCONCLUSIONSnIn pubertal children, sexual maturation, BMI, dietary intervention (in girls), and dietary cholesterol (in boys) were significant in determining LDL-C. Sexual maturation was the factor associated with the greatest difference in LDL-C. Clinicians screening for dyslipidemia or following dyslipidemic children should be aware of the powerful effects of pubertal change on measurements of lipoproteins.