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Biomedical subjects

W H Dietz

Publications and source records attributed to W H Dietz.

At least 19 recordsLinked to original sources
PubMed2006

Dietary pattern as a predictor of change in BMI z-score among girls.

OBJECTIVES: To describe child and adolescent dietary patterns and to determine associations between childhood dietary pattern and longitudinal change in body mass index (BMI) z-score among girls. POPULATION AND METHODS: Healthy girls (n = 101) aged 8-12 years at baseline and 11-19 years at follow-up participated in a longitudinal study of growth and development. Participants kept 7-day dietary records at two points in time. We incorporated time of day, frequency, and amount of energy consumed (defined as percentage of total energy consumed per dietary event) when characterizing dietary patterns. RESULTS: Girls ate an average of 4-5 times per day and consumed most energy in the afternoon and in the evening/night, rather than in the morning. After controlling for baseline BMI, the mean percentage of daily energy consumed in the evening/night was positively associated with change in BMI z-score (P = 0.039). Eating between 4.0 and 5.9 times per day overall and no more than 1.9 times in the evening/night daily were negatively associated with change in BMI z-score (P = 0.002 and 0.047, respectively), after controlling for baseline BMI z-score. DISCUSSION: Recommendations to decrease the percentage of energy coming from the evening/night meal and the number of dietary events to no more than six times per day and two times in the evening/night should be evaluated in future longitudinal investigations.

Anthropometry↗
PubMed2005

Relation of BMI to fat and fat-free mass among children and adolescents.

OBJECTIVE: Although the body mass index (BMI, kg/m2) is widely used as a surrogate measure of adiposity, it is a measure of excess weight, rather than excess body fat, relative to height. We examined the relation of BMI to levels of fat mass and fat-free mass among healthy 5- to 18-y-olds. METHODS AND PROCEDURES: Dual-energy X-ray absorptiometry was used to measure fat and fat-free mass among 1196 subjects. These measures were standardized for height by calculating the fat mass index (FMI, fat mass/ht2) and the fat-free mass index (FFMI, fat-free mass/ht2). RESULTS: The variability in FFMI was about 50% of that in FMI, and the accuracy of BMI as a measure of adiposity varied greatly according to the degree of fatness. Among children with a BMI-for-age > or =85th P, BMI levels were strongly associated with FMI (r=0.85-0.96 across sex-age categories). In contrast, among children with a BMI-for-age <50th P, levels of BMI were more strongly associated with FFMI (r=0.56-0.83) than with FMI (r=0.22-0.65). The relation of BMI to fat mass was markedly nonlinear, and substantial differences in fat mass were seen only at BMI levels > or =85th P. DISCUSSION: BMI levels among children should be interpreted with caution. Although a high BMI-for-age is a good indicator of excess fat mass, BMI differences among thinner children can be largely due to fat-free mass.

Absorptiometry, Photon↗
PubMed2004

The relation of obesity throughout life to carotid intima-media thickness in adulthood: the Bogalusa Heart Study.

OBJECTIVE: Although obese children are at increased risk for coronary heart disease in later life, it is not clear if this association results from the persistence of childhood obesity into adulthood. We examined the relation of adiposity at various ages to the carotid intima-media thickness (IMT) at age 35 y. DESIGN: Prior to the determination of IMT by B-mode ultrasound, subjects (203 men, 310 women) had, on average, six measurements of body mass index (BMI) and triceps skinfold thickness (TSF) between the ages of 4 and 35 y. Mixed regression models for longitudinal data were used to assess the relation of these characteristics to adult IMT. RESULTS: Overall, adult IMT was associated with levels of both BMI and TSF (P<0.001), with the magnitudes of the associations with childhood adiposity comparable to those with adult levels of BMI and TSF. Furthermore, adult obesity modified the association between childhood adiposity and IMT: high IMT levels were seen only among overweight (BMI > or =95th percentile) children who became obese (BMI > or =30 kg/m2) adults (P<0.01 for linear trend). In contrast, IMT levels were not elevated among (1) overweight children who were not obese in adulthood, or among (2) thinner children who became obese adults. CONCLUSIONS: These results emphasize the adverse, cumulative effects of childhood-onset obesity that persists into adulthood. Since many overweight children become obese adults, the prevention of childhood obesity should be emphasized.

Adipose Tissue↗
PubMed2004

Food purchased away from home as a predictor of change in BMI z-score among girls.

OBJECTIVES: To assess the relationship between eating food purchased away from home (FAH) and longitudinal change in body mass index (BMI) z-score among girls, and to assess the longitudinal tracking of eating FAH from childhood through adolescence. DESIGN: Participants kept 7-day dietary records at two points in time. The records included the place and time for all foods consumed. We recorded how often participants ate FAH, calculated the percent of total energy derived from FAH, and classified foods as quick-service food, coffee-shop food, or restaurant food. PARTICIPANTS: Healthy girls (n=101) between the ages of 8 and 12 y at baseline and 11 and 19 y at follow-up participated in a longitudinal study of growth and development at the Massachusetts Institute of Technology. STATISTICAL ANALYSES: Analysis of variance was used to assess the relationship between change in BMI z-score and both the frequency of eating FAH and energy derived from eating FAH. The participants' baseline BMI z-score was a significant covariate and was controlled for in both models. We used the kappa coefficient to assess FAH tracking from childhood through adolescence. RESULTS: The frequency of eating quick-service food at baseline was positively associated with change in BMI z-score (F=6.49, P<0.01). Participants who ate quick-service food twice a week or more at baseline had the greatest mean increase in BMI z-score compared to those who ate quick-service food once a week or not at all. Quick-service food eating tracked slightly from childhood through adolescence (k=0.17, P<0.05). DISCUSSION: Adolescent girls who eat quick-service food twice a week or more are likely to increase their relative BMI over time.

Adolescent↗
PubMed2004

Relationship between temperament, nonresting energy expenditure, body composition, and physical activity in girls.

OBJECTIVES: To assess the extent that predilection for movement, as measured by a temperament questionnaire (activity temperament), contributes to nonresting energy expenditure and body composition in girls. DESIGN, SETTING, AND PARTICIPANTS: Baseline data for 196 premenarcheal non-obese girls aged 8-12 y were obtained from a longitudinal study of growth and development. The association of activity temperament with nonresting energy expenditure in girls with low and high levels of physical activity was evaluated, as was the association of activity temperament with body composition. MEASURES: Maternal reports of child activity temperament were obtained by questionnaire. Nonresting energy expenditure was calculated as total energy expenditure (measured by doubly labeled water) minus resting energy expenditure (obtained by indirect calorimetry). Body composition was estimated by total body water. Questionnaires and activity diaries were used to assess physical activity and sedentary behavior. RESULTS: Higher activity temperament was associated with higher nonresting energy expenditure after multivariate control for weight, vigorous activity, walking and light activity, and television viewing, although activity temperament did not account for a large percentage of the variability in nonresting energy expenditure (partial squared correlation coefficient=0.03). In girls with physical activity levels below the median, high activity temperament was associated with a mean+/-s.d., nonresting energy expenditure of 310+/-138 kJ (74+/-33 kcal) above that of girls with a low activity temperament. Girls with a high activity temperament had less body fat than did girls with a low activity temperament (21.6 vs 24.5%, a difference of 2.9 percentage points; 95% confidence interval, 1.3-4.4 percentage points). CONCLUSION: Predilection for movement, as measured by a temperament questionnaire, contributes to nonresting energy expenditure and may be useful in capturing an aspect of energy expenditure in population studies. The cross-sectional observation that girls with a high activity temperament were leaner than girls with a low activity temperament suggests that a constitutional predilection for movement may play a role in the development of obesity.

Anthropometry↗
PubMed2004

Inter-relationships among childhood BMI, childhood height, and adult obesity: the Bogalusa Heart Study.

OBJECTIVE: Although the body mass index (BMI, mass index, kg/m2) is widely used as a surrogate measure of adiposity, it is moderately associated (r approximately 0.3) with height among children. We examined whether the resulting preferential classification of taller children as overweight is appropriate. DESIGN: Cross-sectional analyses of children (ages, 3-17 y) examined the relation of height to adiposity (as assessed by BMI and skinfold thicknesses) and fasting levels of insulin. Longitudinal analyses examined the relation of childhood height and weight-height indices to adult (mean age, 25 y) levels of adiposity and fasting insulin. SUBJECTS: Children (n=11,406) and adults (n=2911) who had participated in the Bogalusa Heart Study. MEASUREMENTS: We constructed three weight-height indices: BMI, W/H3, and W/Hp. The triceps and subscapular skinfolds, as well as fasting levels of insulin, were also measured. RESULTS: The classification of children as overweight (BMI-for-age > or =95th percentile) varied markedly by height, with a 10-fold difference in the prevalence of overweight across quintiles of height between the ages of 3 and 10 y. Childhood height, however, was also related to skinfold thicknesses and insulin levels, and all associations were modified in a similar manner by age. Furthermore, childhood height was related to adult adiposity, and of the three childhood weight-height indices, BMI showed the strongest associations with adult adiposity. CONCLUSIONS: Because BMI reflects the positive association between height and adiposity among children, it is a better weight-height index than is either W/H3 or W/Hp.

Adolescent↗
PubMed2003

Energy cost of physical activities in 12-y-old girls: MET values and the influence of body weight.

BACKGROUND: Few data exist on the energy cost of specific activities in children. The influence of body weight on the energy cost of activity when expressed as metabolic equivalents (METs) has not been vigorously explored. OBJECTIVE: To provide MET data on five specific activities in 12-y-old girls and to test the hypothesis that measured MET values are independent of body weight. SUBJECTS AND METHODS: In 17 12-y-old girls, resting metabolic rate (RMR) and the energy expended while sitting, standing, walking on a flat treadmill at 3.2 and at 4.8 km/h, and walking on a treadmill at a 10% incline at 4.8 km/h were measured using indirect calorimetry. MET values were calculated by dividing the energy expenditure of an activity by the subject's RMR. The influence of body weight was assessed using simple linear regression. RESULTS: The observed METs were more consistent with published values for similar activities in adults than those offered for children. Body weight was a statistically significant predictor of the MET of all three walking activities, but not the MET of sitting or standing. Body weight explained 25% of the variance in the MET value for walking at 3.2 km/h, 39% for walking at 4.8 km/h, and 63% for walking at a 10% incline at 4.8 km/h. CONCLUSION: METs for the three walking activities were not independent of body weight. The use of average MET values to estimate the energy cost of these three activities would result in an underestimation of their energy cost in heavier girls and an overestimation in lighter girls. These results suggest that the estimation of total energy expenditure from activity diary, recall, and direct observation data using average MET values may be biased by body weight.

Basal Metabolism↗
PubMed2002

Body weight and obesity in adults and self-reported abuse in childhood.

BACKGROUND: Little is known about childhood factors and adult obesity. A previous study found a strong association between childhood neglect and obesity in young adults. OBJECTIVE: To estimate associations between self-reported abuse in childhood (sexual, verbal, fear of physical abuse and physical) adult body weight, and risk of obesity. DESIGN: Retrospective cohort study with surveys during 1995-1997. PATIENTS: A total of 13,177 members of California health maintenance organization aged 19-92 y. MEASUREMENTS: Body weight measured during clinical examination, followed by mailed survey to recall experiences during first 18 y of life. Estimates adjusted for adult demographic factors and health practices, and characteristics of the childhood household. RESULTS: Some 66% of participants reported one or more type of abuse. Physical abuse and verbal abuse were most strongly associated with body weight and obesity. Compared with no physical abuse (55%), being 'often hit and injured' (2.5%) had a 4.0 kg (95% confidence interval: 2.4-5.6 kg) higher weight and a 1.4 (1.2-1.6) relative risk (RR) of body mass index (BMI) > or = 30. Compared with no verbal abuse (53%), being 'often verbally abused' (9.5%) had an RR of 1.9 (1.3-2.7) for BMI > or = 40. The abuse associations were not mutually independent, however, because the abuse types strongly co-occurred. Obesity risk increased with number and severity of each type of abuse. The population attributable fraction for 'any mention' of abuse (67%) was 8% (3.4-12.3%) for BMI > or = 30 and 17.3% (-1.0-32.4%) for BMI > or = 40. CONCLUSIONS: Abuse in childhood is associated with adult obesity. If causal, preventing child abuse may modestly decrease adult obesity. Treatment of obese adults abused as children may benefit from identification of mechanisms that lead to maintenance of adult obesity.

Adult↗
PubMed2001

Impact of overweight on the risk of developing common chronic diseases during a 10-year period.

BACKGROUND: Overweight adults are at an increased risk of developing numerous chronic diseases. METHODS: Ten-year follow-up (1986-1996) of middle-aged women in the Nurses' Health Study and men in the Health Professionals Follow-up Study to assess the health risks associated with overweight. RESULTS: The risk of developing diabetes, gallstones, hypertension, heart disease, and stroke increased with severity of overweight among both women and men. Compared with their same-sex peers with a body mass index (BMI) (calculated as weight in kilograms divided by the square of height in meters) between 18.5 and 24.9, those with BMI of 35.0 or more were approximately 20 times more likely to develop diabetes (relative risk [RR], 17.0; 95% confidence interval [CI], 14.2-20.5 for women; RR, 23.4; 95% CI, 19.4-33.2 for men). Women who were overweight but not obese (ie, BMI between 25.0 and 29.9) were also significantly more likely than their leaner peers to develop gallstones (RR, 1.9), hypertension (RR, 1.7), high cholesterol level (RR, 1.1), and heart disease (RR, 1.4). The results were similar in men. CONCLUSIONS: During 10 years of follow-up, the incidence of diabetes, gallstones, hypertension, heart disease, colon cancer, and stroke (men only) increased with degree of overweight in both men and women. Adults who were overweight but not obese (ie, 25.0 < or = BMI < or = 29.9) were at significantly increased risk of developing numerous health conditions. Moreover, the dose-response relationship between BMI and the risk of developing chronic diseases was evident even among adults in the upper half of the healthy weight range (ie, BMI of 22.0-24.9), suggesting that adults should try to maintain a BMI between 18.5 and 21.9 to minimize their risk of disease.

Body Mass Index↗
PubMed2001

C-reactive protein and body mass index in children: findings from the Third National Health and Nutrition Examination Survey, 1988-1994.

OBJECTIVES: To examine the relationship between C-reactive protein (CRP) concentration and body mass index (BMI) in children. STUDY DESIGN: With the use of data from 5305 children aged 6 to 18 years in the Third National Health and Nutrition Examination Survey (1988 to 1994), a cross-sectional health survey, we examined whether CRP concentrations were elevated among overweight children. RESULTS: Among children whose BMI was below the age- and sex-specific 15th percentile, 6.6% of boys and 10.7% of girls had an elevated CRP concentration (>2.1 mg/L) compared with 24.2% of boys and 31.9% of girls whose BMI was > or =95th percentile. After adjustment was done for age, sex, race or ethnicity, poverty income ratio, high-density lipoprotein cholesterol concentration, white blood cell count, and history of chronic bronchitis, the adjusted odds of having an elevated CRP concentration were 2.20 (95% CI 1.30, 3.75) for children with a BMI of 85th to <95th percentile and 4.92 (95% CI 3.39, 7.15) for children with a BMI of > or =95th percentile compared with children who had a BMI of 15th to <85th percentile. The associations did not differ significantly by age, sex, or race or ethnicity. CONCLUSIONS: In a large representative sample of US children, CRP concentration was significantly elevated among children with a BMI > or=85th percentile, thus confirming previous findings of this association in children and extending previous research in adults to children. Excess body weight may be associated with a state of chronic low-grade inflammation in children.

Adolescent↗
PubMed2001

Preventing obesity in children and adolescents.

In this review, we address the natural history of obesity in children, the most promising family- and school-based approaches to the prevention of obesity, and the barriers and opportunities associated with secondary prevention. In childhood, the most important periods of risk appear to be the periods of adiposity rebound and adolescence. Caution regarding the period of adiposity rebound is still warranted, because it is not yet clear that early rebound is attributable to changes in body fat. Families and schools represent the most important foci for preventive efforts in children and adolescents. One productive approach is to proceed from an examination of factors that affect energy balance to the identification of more proximal influences on those factors. This approach may help to narrow the strategies necessary to prevent or treat childhood obesity. For example, television viewing affects both energy intake and energy expenditure, and therefore represents a logical target for interventions. Anticipatory guidance by pediatricians may offer an effective mechanism by which to change parental attitudes and practices regarding television viewing. A similar process is used to emphasize the potential influence of school-based interventions directed at changes in food choices and sedentary behavior.

Adolescent↗
PubMed2001

Nutritional rickets in Georgia.

Opinions expressed in commentaries are those of the authors and not necessarily those of the American Academy of Pediatrics or its Committees. Commentaries are not peer-reviewed.

Breast Feeding↗
PubMed2001

Relationship of childhood obesity to coronary heart disease risk factors in adulthood: the Bogalusa Heart Study.

BACKGROUND: Childhood obesity is related to adult levels of lipids, lipoproteins, blood pressure, and insulin and to morbidity from coronary heart disease (CHD). However, the importance of the age at which obesity develops in these associations remains uncertain. OBJECTIVE AND DESIGN: We assessed the longitudinal relationship of childhood body mass index (BMI, kg/m(2)) to adult levels of lipids, insulin, and blood pressure among 2617 participants. All participants were initially examined at ages 2 to 17 years and were reexamined at ages 18 to 37 years; the mean follow-up was 17 years. RESULTS: Of the overweight children (BMI >/=95th percentile), 77% remained obese (>/=30 kg/m(2)) as adults. Childhood overweight was related to adverse risk factor levels among adults, but associations were weak (r ~ 0.1-0.3) and were attributable to the strong persistence of weight status between childhood and adulthood. Although obese adults had adverse levels of lipids, insulin, and blood pressure, levels of these risk factors did not vary with childhood weight status or with the age (</=8 years, 12-17 years, or >/=18 years) of obesity onset. CONCLUSIONS: Additional data are needed to assess the independent relationship of childhood weight status to CHD morbidity. Because normal-weight children who become obese adults have adverse risk factor levels and probably will be at increased risk for adult morbidity, our results emphasize the need for both primary and secondary prevention.

Adolescent↗
PubMed2001

Interventions for weight loss and weight gain prevention among youth: current issues.

The recent increase in the prevalence of paediatric obesity is one of the most pressing public health concerns today because of the immediate and long term health consequences associated with this often intractable disease. Efforts are currently being made to reduce the prevalence of paediatric obesity. Youth weight loss studies have produced significant long term results. Most of these programmes included behaviour modification, diet and exercise. Studies have suggested that lifestyle exercise programmes may produce the best long term results. Effective components of these programmes appear to be parental involvement, reduced intake of foods having high energy density and reductions in physical inactivity. Future weight loss studies need to determine the type, intensity, and duration of exercise that will produce acceptable adherence and consequent long term weight loss, and to ascertain the reinforcing factors that determine youth behaviour choice. Weight gain prevention interventions for youth are clearly in their infancy. This review describes 3 completed and 2 ongoing weight gain prevention trials. One study showed reductions in the prevalence of obesity among junior high school girls, but not among boys. Another study among elementary school students showed significant mean decreases in body mass index in boys and girls following an intervention specifically to reduce time spent viewing television. Whether these studies altered food intake or increased physical activity remains unclear. A combination of weight loss treatment and weight gain prevention strategies employed in parallel is likely to yield the greatest benefits. Development and testing of novel intervention strategies, using innovative behavioural approaches to increase the likelihood that children will adopt healthy dietary, physical activity, and sedentary behaviour patterns, holds great promise to significantly reduce the epidemic of obesity.

Adolescent↗