Childhood obesity.

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.

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.

Self-perceived barriers to activity participation among sedentary adolescent girls.

PURPOSE: Potential barriers to activity participation were surveyed among adolescent girls and corroborated with other reported information. METHODS: Among 2379 black and white girls enrolled in the NHLBI Growth and Health Study since ages 9 or 10 yr, those reporting weekly activity frequency as "sometimes" or "rarely" were surveyed for three consecutive years from ages 16 or 17 yr. Barriers to activity were assessed using a 10-item questionnaire. Responses were cross-examined with other reported information. Race-specific longitudinal regression examined the impact of barrier scores on activity levels and also potential factors having an impact on barrier scores. RESULTS: Approximately half of the cohort was screened as "sedentary" with a trend toward an increasing proportion with age. Lack of time was cited by 60% of sedentary girls as the leading barrier to activity participation for all 3 yr. Other frequently cited barriers to activity included "I'm too tired" and "They don't interest me." No differences were seen in hours at work or in household chores between those who cited lack of time and those who did not. Barrier score was a significant predictor of habitual activity scores. For both races, body mass index and "would rather do other things than exercise" were significant predictors of barriers, but work, parental education, TV watching, and childbirth were not significant. CONCLUSION: Self-reported barriers to activity participation among sedentary girls were shown to be primarily internal and uncorrelated with other corresponding external factors.

Racial differences in correlates of misreporting of energy intake in adolescent females.

OBJECTIVE: To determine the extent of misreporting of energy intake (EI) and its anthropometric, demographic, and psychosocial correlates in a bi-racial cohort of young women. RESEARCH METHODS AND PROCEDURES: This was a cross-sectional study of 60 black and 60 white young women, 18 to 21 years old, enrolled in a longitudinal study. Total energy expenditure was assessed using doubly labeled water. Self-reported EI was obtained from 3-day food records. BMI was computed from height and weight. Fat mass was assessed by DXA. Multivariate analyses examined racial differences on the extent of misreporting and its effect on other potential correlates of misreporting. Race-specific step-wise linear regression analysis was performed to examine the effect of BMI, parental education, and drive for thinness on misreporting of EI. RESULTS: More white women tended to under-report EI than black women (22% vs. 13%, p = 0.07). In black women, under-reporting was significantly (p = 0.01) associated with drive for thinness score but was only marginally (p = 0.1) associated with BMI. Each point increase in drive for thinness score was associated with under-reporting by 40 kcal/d. In white women, under-reporting was significantly (p = 0.03) associated with higher parental education by 440 kcal/d and also only marginally (p = 0.09) with BMI. DISCUSSION: This tendency for under-reporting of EI limits the use of self-reported EI in studying energy balance in free-living subjects. Most black and almost all white women in their late teens significantly under-reported their EI, whereas under-reporting was not as evident among lean young black women.

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

BACKGROUND: The 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. METHODS: BMI 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. FINDINGS: Each 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. INTERPRETATION: Changes 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.

Macronutrient intake of black and white adolescent girls over 10 years: the NHLBI Growth and Health Study.

OBJECTIVE: To compare age-related changes in macronutrient and cholesterol intake between black and white girls, compare intakes with National Cholesterol Education Program (NCEP) recommendations, and examine sociodemographic associations with macronutrient intake. DESIGN: Cohort study with 3-day food records collected over 10 years. SUBJECTS: 2,379 girls, 1,166 white and 1,213 black, age 9 to 10 years at baseline, recruited from three geographic locations. Statistical Analysis Longitudinal generalized estimating equation (GEE) regression models examined the relationships of age, ethnicity, and sociodemographic factors with macronutrient and cholesterol intake and with percentage of girls meeting NCEP recommendations. RESULTS: Total and saturated fat intakes decreased with age, more in white girls than black girls, from 35.1% and 13.6% kcal at age 9 to 29.3% and 10.4% at age 19 for white girls and from 36.5% and 13.4% kcal at age 9 to 35.1% and 11.7% kcal at age 19 for black girls. Dietary cholesterol decreased with age, but decreased more in white girls than black girls (range 95 to 119 mg/1,000 kcal for white girls and 119 to 132 mg/1,000 kcal for black girls). Depending on age, 7% to 51% of white girls and 8% to 26% of black girls met NCEP recommendations for total fat (

A summary of results of the Dietary Intervention Study in Children (DISC): lessons learned.

Prevention of cardiovascular disease must begin in childhood, preferably before risk factors develop. Elevated low-density lipoprotein cholesterol levels in children are likely to track over time and become high-risk levels in adults. The Dietary Intervention Study in Children (DISC) was a multicenter, collaborative randomized trial in pre-adolescent children designed to test the efficacy and safety of a dietary intervention to lower saturated fat and cholesterol intake among growing children with elevated low-density lipoprotein cholesterol. Numerous DISC results, which include findings on lipids-lipoproteins, genetics, and nutrient adequacy, as well as descriptions of the behavioral intervention strategies, have been reported. A summary of practical findings and their potential clinical applications have not previously been published. Highlights of key lessons learned from DISC and translational applications of potential interest to nurses and other health care providers are presented.

Obesity development during adolescence in a biracial cohort: the NHLBI Growth and Health Study.

OBJECTIVE: The National Heart, Lung, and Blood Institute Growth and Health Study (NGHS) is a 10-year study to investigate the development of obesity in black and white girls during adolescence and its environmental and psychosocial correlates. The purpose of this report was to examine changes in the annual prevalence rates of overweight and obesity in the NGHS cohort from ages 9 to 19 years. PARTICIPANTS AND SETTING: A total of 2379 black and white girls, aged 9 to 10 years, were recruited from schools in Richmond, California, and Cincinnati, Ohio, and from families enrolled in a health maintenance organization in the Washington, DC area. Participant eligibility was limited to girls and their parents who declared themselves as being either black or white and who lived in racially concordant households. DESIGN AND STATISTICAL ANALYSIS: The NGHS is a multicenter prospective study of a biracial cohort followed annually from ages 9 to 10 years through 18 to 19 years. The prevalence of overweight and obesity was based on age-specific > or =85th and > or =95th percentile values, respectively, for body mass index based on the 1960-1965 National Health Examination Survey reference population. MAIN OUTCOME MEASURES: The main outcome measures were body mass index (weight in kilograms divided by height in meters, squared) and proportions of girls who were "overweight" and "obese" by age and race. RESULTS: The prevalence of overweight was 37% higher in blacks as compared with whites (30.6% vs 22.4%) even by age 9. The rate of overweight almost doubled in both groups during the 10-year period. By age 19, the rate of overweight was 56.9% in black and 41.3%, in white girls. The prevalence of obesity was 17.7% in black and 7.7% in white girls at 9 years old, and the rates also doubled during the study period. CONCLUSIONS: The doubling in the prevalence of overweight and obesity during adolescence in black and white NGHS girls was surprising. By age 19, more than half of black girls were overweight and more than one third were obese. Almost half of white girls were overweight and almost 1 of 5 girls were obese. These findings should sound an alarm for all primary care physicians and public health professionals to take heed of what is happening to our youth.

Decline in physical activity in black girls and white girls during adolescence.

BACKGROUND: Physical activity declines during adolescence, but the underlying reasons remain unknown. METHODS: We prospectively followed 1213 black girls and 1166 white girls enrolled in the National Heart, Lung, and Blood Institute Growth and Health Study from the ages of 9 or 10 to the ages of 18 or 19 years. We used a validated questionnaire to measure leisure-time physical activity on the basis of metabolic equivalents (MET) for reported activities and their frequency in MET-times per week; a higher score indicated greater activity. RESULTS: The respective median activity scores for black girls and white girls were 27.3 and 30.8 MET-times per week at base line and declined to 0 and 11.0 by year 10 of the study (a 100 percent decline for black girls and a 64 percent decline for white girls, P<0.001). By the age of 16 or 17 years, 56 percent of the black girls and 31 percent of the white girls reported no habitual leisure-time activity. Lower levels of parental education were associated with greater decline in activity for white girls at both younger ages (P<0.001) and older ages (P=0.005); for black girls, this association was seen only at the older ages (P=0.04). Pregnancy was associated with decline in activity among black girls (P<0.001) but not among white girls, whereas cigarette smoking was associated with decline in activity among white girls (P<0.001). A higher body-mass index was associated with greater decline in activity among girls of both races (P< or =0.05). CONCLUSIONS: Substantial declines in physical activity occur during adolescence in girls and are greater in black girls than in white girls. Some determinants of this decline, such as higher body-mass index, pregnancy, and smoking, may be modifiable.

Racial differences in the relation between uncoupling protein genes and resting energy expenditure.

BACKGROUND: Lower resting energy expenditure (REE) in African American women may contribute to their obesity. The identification of uncoupling protein (UCP) genes has fueled a search for genes involved in energy metabolism in humans. OBJECTIVE: We examined variation in REE in relation to variation in UCP1, UCP2, and UCP3 in 141 women aged 18-21 y. DESIGN: Standard methods were used for REE measurements and genetic analysis. Body composition was determined with the use of dual-energy X-ray absorptiometry. Multivariate analysis was used to examine the effect of genotypes on REE and on fat mass in relation to other potentially confounding variables. RESULTS: REE was 295 kJ/d lower in African American women than in white women. No significant variation in REE was seen for UCP1, UCP2, and UCP3 (p-55; exon 3a; and exon 3b) variants after adjustment for other variables including smoking status. For the UCP3 exon 5 variant, REE was significantly (P = 0.019) lower in African American women with the CC genotype than in those with the TT genotype. In African American women, there was a significant trend (P = 0.012) toward lower REE and a weak but nonsignificant trend (P = 0.1) toward greater fat mass across the 3 genotypes (TT, CT, and CC). CONCLUSIONS: The significant and dose-dependent relation between lower REE and the C allele suggests that it may be a thrifty allele. The presence of this parsimonious energy metabolism in African American women, possibly linked to UCP3, may be implicated in their susceptibility to obesity. The absence of a UCP3 effect in white women is intriguing and needs to be explored to further understand possible interactions between UCP3 and other genes.