Search

Background: Identification of the factors that influence children's participation in vigorous activity is essential to the development of effective intervention strategies aimed at the prevention of cardiovascular disease and obesity., Methods: Correlates of intent to participate in vigorous activity were assessed among 310 fifth and eighth graders in Cambridge, Massachusetts, through the development and administration of a questionnaire based on the Theory of Planned Behavior, an extension of the Theory of Reasoned Action, which includes the domain of perceived behavioral control (how easy or difficult it is to engage in vigorous activity). Heights and weights were measured and questionnaires were completed during physical education classes., Results: Perceived behavioral control and attitude predicted children's intent to participate. How much a child agreed s/he was good at doing vigorous activity predicted perceived behavioral control. In each grade, girls reported being less good at vigorous activity than did boys. Eighth-grade girls reported significantly fewer hours of vigorous activity than did eighth-grade boys., Conclusions: Our findings suggest that gender differences related to intent to participate in vigorous activity, perceived behavioral control, and sense of competency are evident in eighth grade and may begin in fifth grade. These gender differences in perception therefore precede the gender difference in participation in vigorous activity demonstrated among ninth graders in the 1990 Youth Risk Behavior Survey. Promotion of activities children enjoy, and in which they feel a sense of competency, is likely to sustain participation in vigorous activity throughout adolescence and possibly reduce the prevalence of obesity.

Objective: Inconsistent findings reported for the effect of physical activity on lipids, lipoproteins, and blood pressure in children may be due to errors inherent in the methods used to measure physical activity, lack of control for other cardiovascular risk factors, or both. The purpose of this study was to evaluate the association between physical activity assessed using direct measures of energy expenditure and cardiovascular risk factors, controlling for dietary intake and percent body fat., Methods: Nonresting energy expenditure was determined in 49 8- to 11-year-old girls from measurements of daily energy expenditure (using doubly-labeled water, 2H2(18)O) and resting metabolic rate (using indirect calorimetry). Self-reported recall of the hours of participation in physical activities of at least moderate intensity (energy expenditure at least four times the resting metabolic rate, METS > or = 4) during the previous year was also obtained. Percent body fat was estimated from the measurement of total body water with H2(18)O. Concentrations of total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol (LDL-C), apolipoprotein B (apo B), apo A-I, lipoprotein (a), insulin, and estradiol, as well as the waist-to-hip ratio, systolic blood pressure, diastolic blood pressure, and dietary intake from 7-day food records were measured. Data were analyzed using Pearson product-moment correlation and stepwise multiple regression., Results: Self-reported hours of participation in activities with METS (metabolic equivalents) of 4 or greater significantly predicted LDL-C and apo B concentrations, even after adjustment for percent body fat and percentage of dietary energy from saturated fat. Nonresting energy expenditure adjusted for weight, a measure of the energy spent on physical activity, did not predict LDL-C or high-density lipoprotein cholesterol concentrations. Body mass index and insulin concentration predicted systolic and diastolic blood pressure, respectively., Conclusions: These findings suggest that the intensity of physical activity may be a more important determinant of LDL-C in children than the energy spent on physical activity.

Background and Methods: The prevalence of obesity among children and adolescents has increased, and television viewing has been suggested as a cause. We examined the relation between hours of television viewed and the prevalence of overweight in 1990, and the incidence and remission of overweight from 1986 to 1990 in a nationally representative cohort of 746 youths aged 10 to 15 years in 1990 whose mothers were 25 to 32 years old. Overweight was defined as a body mass index higher than the 85th percentile for age and gender., Results: We observed a strong dose-response relationship between the prevalence of overweight in 1990 and hours of television viewed. The odds of being overweight were 4.6 (95% confidence interval, 2.2 to 9.6) times greater for youth watching more than 5 hours of television per day compared with those watching 0 to 2 hours. When adjustments were made for previous overweight (in 1986), baseline maternal overweight, socioeconomic status, household structure, ethnicity, and maternal and child aptitude test scores, results were similar (odds ratio, 5.3; 95% confidence interval, 2.3 to 12.1). We also found significant relations between television viewing and increased incidence and decreased remission of overweight during this 4-year period, adjusted for baseline covariates. The adjusted odds of incidence were 8.3 (95% confidence interval, 2.6 to 26.5) times greater for youth watching more than 5 hours of television per day compared with those watching for 0 to 2 hours. Estimates of attributable risk indicate that more than 60% of overweight incidence in this population can be linked to excess television viewing time., Conclusion: Television viewing affects overweight among youth, and reductions in viewing time could help prevent this increasingly common chronic health condition.

Several different equations based on height, weight, sex, and age are available to predict metabolic rate in children and adolescents. The purpose of this study was to determine which of the published standardized equations most accurately predicts metabolic rate in premenarcheal girls. Resting metabolic rate (RMR) was measured in 186 premenarcheal girls by using open-circuit indirect calorimetry with a ventilated hood. Measured RMR was compared with equations provided by the FAO/WHO/UNU, the Mayo Clinic, and Robertson and Reid for girls of the same age. The accuracy of each equation differed for each Tanner stage. The Mayo Clinic standards significantly differed from measured RMR among girls in Tanner stages 1 and 2. The Robertson and Reid standards differed from measured RMR for girls in Tanner stage 1. Only the FAO/WHO/UNU equation predictions did not differ from measured RMR for all Tanner stages studied. These results indicate that the FAO/WHO/UNU equation is the best predictor of RMR in premenarcheal girls at different stages of development. Furthermore, because RMR measured under inpatient and outpatient conditions did not differ significantly, an overnight measurement is not necessary for a reliable determination of RMR.

Energy expenditure was measured in a group of 7 subjects who received two isocaloric isonitrogenous diets for a period of 9-21 days with a 4-10-day break between diets. Diet 1 was a high-fat diet ( 83.5 +/- 3.6% of total energy). Diet 2 was a high carbohydrate diet ( 83.1 +/- 3.7% of total energy). Resting and postprandial resting metabolic rate were measured by open circuit indirect calorimetry 2-4 times during each metabolic period. Total energy expenditure (TEE) was measured by the doubly labeled water method over an 8-13-day period. The respiratory quotient was measured 2-4 hours after a meal during each metabolic period for the calculation of total energy expenditure by the doubly labeled water method. Levels of total T3 (TT3), T3 uptake, free thyroid index and T4 were measured at the end of each metabolic period. No significant changes in resting metabolic rate (RMR) were apparent on the two diets (1567 +/- 426 kcal/d high-fat diet and 1503 +/- 412 kcal/d high-carbohydrate diet n=7, p<0.15). Total energy expenditure measured in 5 subjects was significantly higher during the high-carbohydrate phase of the diet (2443 +/- 422 vs. 2078 +/- 482 kcal/d p<0.05). Activity estimated from TEE/RMR was greater on the high-carbohydrate diet but only approached statistical significance (p<0.06). Total T3 was significantly lower and free thyroid index and T3 uptake were significantly higher at the end of the high fat diet in comparison to the high-carbohydrate diet. These data suggest that individual tolerance to a high-fat diet varies considerably and may significantly lower TEE by changing levels of physical activity. The explanation for changes in thyroid hor. mone levels independent of changes in metabolic rate remains unclear.

Critical periods of development have been well recognized for many behavioral and developmental processes. However, as others have pointed out, such periods have not been widely reported for nutritional diseases. Many observations suggest that two and possibly three critical periods exist for the development of obesity and its complications. These include gestation and early infancy, the period of adiposity rebound that occurs between 5 and 7 y of age, and adolescence. Obesity that begins at these periods appears to increase the risk of persistent obesity and its complications. The mechanisms that account for the increased risk associated with obesity at these ages remain unclear. Nonetheless, the existence of critical periods should serve to focus preventive efforts on these developmental stages.

We examined the effect of television viewing on resting metabolic rate (RMR) in a cohort of 9 obese and 18 nonobese girls aged 10.4 +/- 1.1 y. RMR was measured while girls watched television, read, or sat quietly for 15 min. Movement was assessed by using activity monitors and a manual count of movements observed on a videotape. Absolute RMR was greater for the obese girls, but no significant treatment effect existed for absolute RMR within either group. Although measured activity did not differ, observed movements were greater when the girls were sitting quietly. Total observed and measured movements were significantly correlated with the CV of the minute-by-minute RMR. These results suggest that television viewing does not alter RMR. Although children appear to fidget more when sitting quietly than when they read or watch television, fidgeting appears to affect the minute-to-minute variation of RMR rather than the level of resting energy expenditure.

An expert committee was convened to determine specific criteria for overweight to be integrated into routine preventive screening of adolescents. Body mass index (BMI) should be used routinely to screen for overweight adolescents. Youth with BMIs > or = 95th percentile for age and sex, or > 30 (in kg/m2) should be considered overweight and referred for indepth medical follow-up to determine underlying diagnoses. Adolescents with BMIs > or = 85th percentile but < 95th percentile or < or = 30, should be considered at risk of overweight, and should be referred to a second-level screen. The second-level screen includes family history, blood pressure, total cholesterol, large prior increment in BMI, and concern about weight. If youths are positive for any of the items on the second-level screen they should be referred for further medical assessment.

Background and Methods: Overweight in adolescents may have deleterious effects on their subsequent self-esteem, social and economic characteristics, and physical health. We studied the relation between overweight and subsequent educational attainment, marital status, household income, and self-esteem in a nationally representative sample of 10,039 randomly selected young people who were 16 to 24 years old in 1981. Follow-up data were obtained in 1988 for 65 to 79 percent of the original cohort, depending on the variable studied. The characteristics of the subjects who had been overweight in 1981 were compared with those for young people with asthma, musculoskeletal abnormalities, and other chronic health conditions. Overweight was defined as a body-mass index above the 95th percentile for age and sex., Results: In 1981, 370 of the subjects were overweight. Seven years later, women who had been overweight had completed fewer years of school (0.3 year less; 95 percent confidence interval, 0.1 to 0.6; P = 0.009), were less likely to be married (20 percent less likely; 95 percent confidence interval, 13 to 27 percent; P < 0.001), had lower household incomes ($6,710 less per year; 95 percent confidence interval, $3,942 to $9,478; P < 0.001), and had higher rates of household poverty (10 percent higher; 95 percent confidence interval, 4 to 16 percent; P < 0.001) than the women who had not been overweight, independent of their base-line socioeconomic status and aptitude-test scores. Men who had been overweight were less likely to be married (11 percent less likely; 95 percent confidence interval, 3 to 18 percent; P = 0.005). In contrast, people with the other chronic conditions we studied did not differ in these ways from the nonoverweight subjects. We found no evidence of an effect of overweight on self-esteem., Conclusions: Overweight during adolescence has important social and economic consequences, which are greater than those of many other chronic physical conditions. Discrimination against overweight persons may account for these results.

Childhood obesity leads to approximately 30% of adult obesity. However, the natural history of childhood obesity that persists into adulthood suggests that the obese child who becomes an obese adult will have more severe adult obesity than adults whose obesity began in adulthood. Therefore, to the extent that the severity of obesity predicts morbidity, persistence of childhood obesity may be expected to account for a disproportionate share of the adult sequelae of obesity. Fifty-year follow-up studies of a cohort with adolescent obesity have demonstrated that the mortality and morbidity of cardiovascular disease was significantly increased compared with a cohort that was lean throughout adolescence. Furthermore, the effect of adolescent obesity on adult morbidity and mortality appeared independent of the effects of adolescent obesity on adult weight status. Because truncal fat is deposited during adolescence, adolescent onset obesity may entrain both adult obesity and the effects of adolescent onset obesity on mortality and morbidity. These observations suggest that successful treatment of childhood and adolescent obesity is an effective approach to the prevention of severe adult disease. Recently, follow-up of children treated with diet, exercise and behaviour modification showed significantly lower weights 10 years later than children treated in other ways (p < 0.01). These and other family-based treatments appear to be the most appropriate approaches to the treatment of childhood obesity. However, the prevalence of childhood and adolescent obesity suggests that even the most successful treatment may be of limited benefit if it relies on the traditional medical model (doctor/patient interaction).(ABSTRACT TRUNCATED AT 250 WORDS)

Background: Overweight in adults is associated with increased morbidity and mortality. In contrast, the long-term effect of overweight in adolescence on morbidity and mortality is not known., Methods: We studied the relation between overweight and morbidity and mortality in 508 lean or overweight adolescents 13 to 18 years old who participated in the Harvard Growth Study of 1922 to 1935. Overweight adolescents were defined as those with a body-mass index that on two occasions was greater than the 75th percentile in subjects of the same age and sex in a large national survey. Lean adolescents were defined as those with a body-mass index between the 25th and 50th percentiles. Subjects who were still alive were interviewed in 1988 to obtain information about their medical history, weight, functional capacity, and other risk factors. For those who had died, information on the cause of death was obtained from death certificates., Results: Overweight in adolescent subjects was associated with an increased risk of mortality from all causes and disease-specific mortality among men, but not among women. The relative risks among men were 1.8 (95 percent confidence interval, 1.2 to 2.7; P = 0.004) for mortality from all causes and 2.3 (95 percent confidence interval, 1.4 to 4.1; P = 0.002) for mortality from coronary heart disease. The risk of morbidity from coronary heart disease and atherosclerosis was increased among men and women who had been overweight in adolescence. The risk of colorectal cancer and gout was increased among men and the risk of arthritis was increased among women who had been overweight in adolescence. Overweight in adolescence was a more powerful predictor of these risks than overweight in adulthood., Conclusions: Overweight in adolescence predicted a broad range of adverse health effects that were independent of adult weight after 55 years of follow-up.

Childhood obesity is a multifactorial and complex disease. Myths such as those that we have described may distract our patients from the underlying behaviors that contribute to the disease or may deflect the blame perceived by obese patients and their parents. Myths that suggest that the obese are inactive, eat differently, or eat more junk food suggest that obese individuals are socially deviant and justifies the intense discrimination directed against them. The myth that obesity represents an untreatable disease helps free health-care professionals from the responsibility to understand and care for obese children. Dispelling the myths about childhood obesity represents a critical step in prevention and treatment.

The displacement of sports and other physical activities by television and video may contribute to the associations among television viewing, obesity, and reduced physical fitness. Because video games are widely played by children and adolescents, we assessed the metabolic and cardiovascular responses to video game playing. Heart rate, blood pressure, and oxygen consumption were measured serially over 30 minutes in 32 males and females aged 16 to 25 years (mean +/- SEM, 20 +/- 1 years) while they played the "Ms Pac-Man" video game under standard laboratory conditions and compared with measurements made in a standing but inactive position. Playing the video game significantly increased heart rate, systolic and diastolic blood pressure, and oxygen consumption. Energy expenditure increased from 6.08 +/- 0.24 kJ/min while the subjects stood inactive to 10.94 +/- 0.49 kJ/min while they played. The increase in metabolic rate and cardiovascular stimulation was similar in magnitude to mild-intensity exercise.

Body mass index (BMI) and triceps skinfold thickness (TSF) are commonly used measures of adiposity in clinical and epidemiologic studies. The 85th and 95th percentiles of BMI and TSF are often used operationally to define obesity and superobesity, respectively. Race-specific and population-based 85th and 95th percentiles of BMI and TSF for people aged 6-74 y were generated from anthropometric data gathered in the National Health and Nutrition Examination Survey 1 (NHANES I). The complex sample design of the survey is reflected in the reference values presented. Racial differences in these extremes of the distribution do not emerge until adulthood. Researchers may choose population-based, race-specific, or age-specific criteria for obesity on the basis of assumptions underlying their specific research questions.

We measured body composition, resting metabolic rate (RMR), and total energy expenditure (TEE) in a group of adolescents with cerebral palsy (CP) and myelodysplasia (M) aged 13- to 20-y-old using indirect calorimetry and the doubly labeled water method. Fat-free mass (FFM), RMR, and TEE were significantly lower in both the CP and M groups than comparable measurements in a control group of normal adolescent males and females. The ratio of TEE to RMR did not differ between controls and ambulatory M and CP subjects. However, TEE/RMR was significantly lower in the nonambulatory M and CP subjects than in controls (p less than 0.01). Our data indicate that energy requirements are reduced in both populations because both FFM and activity are decreased. Although energy requirements were decreased in both groups, the relationships between FFM and body weight differed. FFM and body weight were significantly correlated with RMR only in the M group. These data suggest that the type of paralysis in a handicapped population may affect resting energy expenditure.

To evaluate the validity of equations for the calculation of basal metabolic rate, we compared measured metabolic rates in a population that included obese and nonobese adolescents with metabolic rates calculated from five equations commonly used to estimate metabolic rate. Of the available options, neither the Mayo Clinic nomogram nor the Food and Agriculture Organization/World Health Organization/United Nations University (FAO/WHO/UNU) equations produced estimates that differed significantly from measured values. In a second cohort of severely obese adolescent girls, the FAO/WHO/UNU equation that included both height and weight provided the most accurate estimate of metabolic rate. Because of their simplicity, we recommend use of the FAO/WHO/UNU equations to estimate metabolic rate in adolescent populations (boys: BMR = 17.5 weight (kg) + 651; girls: BMR = 12.2 weight (kg) + 746). However, when obese cohorts are studied, the FAO/WHO/UNU equation that includes both weight and height predicts metabolic rate most accurately (boys: BMR = 16.6 weight (kg) + 77 height (m) + 572; girls: BMR = 7.4 weight (kg) + 482 height (m) + 217).

As we have indicated, children's television has either a documented or probable effect on a variety of health-related behaviors in children and adolescents in the United States. Studies of cognitive development indicate that television provides a stimulus for learning and that children learn from television. The adverse effects of television appear related to both the time spent watching television and the content of the programs that are viewed. The reviewed observations suggest that a variety of initiatives are warranted to alter the time children spend watching television, the content of programs, and the types of programs for children and adolescents that are produced and broadcast. These initiatives require the development of effective techniques and materials for counseling parents, as well as continued political and legislative activities at the local and national level. We must promote the conviction that time spent in activities other than television viewing will provide our children with the values necessary to understand and interact with an increasingly complex world. Effective governmental action on behalf of children to change television will require a reaffirmation and enforcement of the Public Interest Standard. For half a century, the broadcast media have been licensed to use the airwaves in the public interest. The diversity and magnitude of the adverse effects of television on the health of children strongly suggest that the use of television has not been in the public interest. Although cable television offers multiple alternatives, less than 60% of American households receive cable. Broadcast television still represents the only alternative for 40% of American children. Substantial regulatory change by the current administration is unlikely. Therefore, legislative activity to mandate broadcast practices responsive to the needs of children appears the most appropriate national approach.

Daily metabolizable energy intake (ME) and total daily energy expenditure (TEE) were measured in 28 nonobese and 27 obese adolescents over a 2-wk period. Reported ME was significantly (p less than 0.001) lower than measured TEE in both the nonobese and the obese groups (2193 +/- 618 vs 2755 +/- 600 kcal/d and 1935 +/- 722 vs 3390 +/- 612 kcal/d, respectively). Reported ME as a percentage of TEE was significantly lower in the obese than the nonobese group (58.7 +/- 23.6% vs 80.6 +/- 18.7%, respectively). When reported ME was adjusted to account for changes in body energy stores, reported ME still remained significantly lower than TEE in both groups. ME was highly reproducible over the 2-wk period. Intraclass correlation coefficients among days for subjects with complete 14-d diaries were 0.87 and 0.89 for nonobese and obese groups, respectively. In both groups, interindividual variability in ME was significantly greater than intraindividual variability. Our data suggest that reported ME in nonobese and obese adolescents is not representative of TEE or energy requirements.

Recent studies have documented an increasing prevalence of childhood and adolescent obesity in the United States. These increases will likely result in increased adult obesity because of the tracking of fatness from adolescence into adulthood and the tendency for adults in the United States to become obese as they age. We have identified television viewing as a strong risk factor for childhood and adolescent obesity. Television viewing is associated with both the onset of obesity and a decrease in the remission of obesity and acts by decreasing activity levels and possibly influencing diet. Logistic regressions also document associations between television viewing and obesity among adults. These relationships are greater than those estimated between measures of vigorous physical activity and obesity and indicate the importance of inactivity, to which television viewing contributes substantially. Population dietary intake data indicated no statistically significant change and perhaps some decrease in mean energy intake among children and youth during the same period that obesity was increasing. These data are consistent with the hypothesis that decreases in activity reduce lean body mass and lower energy requirements. We conclude that multiple intervention approaches involving diet, exercise, and restriction of television viewing and other sedentary activities all appear necessary to halt the fattening of America.

Over the past 10 years, seven separate studies of children at risk from undernutrition in Massachusetts have been performed. The surveys have ranged from a statewide health center-based investigation to a house-to-house survey in a public housing project. All included children between 1 and 6 years of age. Chronic undernutrition was defined as a height-for-age less than the 5th percentile of the National Center for Health Statistics growth charts, and acute undernutrition was defined as a weight-for-height less than the 5th percentile. The prevalence of chronic undernutrition was greater than expected in four surveys, whereas no acute undernutrition was observed. The prevalence of obesity, defined as a weight for height greater than the 95th percentile, was increased in four of the seven surveys. These data suggest that chronic undernutrition is increased among children at risk in Massachusetts.

To test the accuracy of self-reported energy intake, reported intake was compared with measured energy expenditure. Results from nine studies were reviewed in which intake data were obtained by recall or weighed record for at least 7 days. Expenditure was measured for 7 days or more by the doubly labelled water method. Individual differences between reported intake and expenditure were large (range +25 to -76%). Group mean differences were smaller. Lean, nonathletic groups living in industrialized countries demonstrated the smallest mean difference between self-reported energy intakes and expenditure (0 to -20%). Obese populations demonstrated the largest mean differences (-35 and -50%), but women living in the Gambia and elite athletes also demonstrated large mean differences. Most of the difference appears to be due to under-reporting, but some subjects lost weight during the reporting period indicating that some of the difference was due to undereating. Because the greatest bias was observed in obese subjects, current methods for self-reported energy intake are not recommended for use in obesity research.

We measured body composition, basal metabolic rate (BMR), and total energy expenditure in 28 nonobese and 35 obese adolescents aged 12-18 y using indirect calorimetry and the doubly labeled water method. BMR was highly correlated with fat-free mass in both the nonobese and obese groups (r = 0.77 and 0.84, respectively). BMR adjusted for fat-free mass was significantly greater in males than females and in the obese subjects. Total energy expenditure was significantly greater in the obese than nonobese cohort but ratios of total energy expenditure/BMR were not significantly different in the two groups (1.79 +/- 0.2 versus 1.68 +/- 0.19, nonobese and obese males and 1.69 +/- 0.28 versus 1.74 +/- 0.19 nonobese and obese females, respectively). These data indicate that BMR and total energy expenditure are not reduced in the already obese adolescent. Therefore, reduced energy expenditure cannot be responsible for the maintenance of obesity in adolescents.

Eating disorders among adolescents in the United States constitute the most frequent nutritional problems in this age group, and their prevalence appears to be increasing. A causal relationship of television viewing to obesity is strongly suggested for children and adolescents. Perhaps as much as 25% of the recent increase in obesity among adolescents may be attributable to increases in television viewing. Associations between television viewing and anorexia and bulimia are less explicit than they are for obesity. Nonetheless, because children and adolescents spend more time viewing television than they do in any activity other than sleep, the world shown on television may acquire a greater reality than the world that is experienced. The low frequency of obesity among televised characters, combined with the frequent food-related references that are contained in both commercials and programming, may promote unrealistic conclusions regarding eating and body weight. Television reflects a cultural contradiction by promoting food consumption and leanness. In this context, bulimia may be viewed as an adaptive response, because only bulimics can eat everything they wish and remain thin.

Nitrogen balance in six obese adolescent boys and three obese girls was studied during two nonconsecutive three-week dietary periods. Protein intake was based on an ideal body weight calculated from the measurement of total body water. The diets consisted of 1.5 gm meat protein/kg IBW/day plus 1.0 gm glucose/kg IBW/day, or an isonitrogenous diet made isocaloric with fat. Each dietary period was preceded by a controlled five-day diet designed to achieve weight maintenance. The first dietary period was followed by a one-month period of re-equilibration. The addition of carbohydrate to protein produced a significantly better cumulative nitrogen balance than P + F. Significant nitrogen losses persisted throughout the entire dietary period of P + F in three patients, but were observed in only one patient during P + G. Lymphopenia occurred in one subject on P + F but did not occur during P + G. Serum albumin concentrations were unchanged on both diets. Transferrin values decreased during P + F, but did not differ significantly from prediet levels during P + G. However, the observation of prolonged nitrogen losses in one subject on P + G and the limited experience with highly restrictive diets in obese adolescents emphasize that such diets must be used with caution and monitored carefully.

One hundred and fifty-eight strains of Venezuelan equine encephalomyelitis virus were typed antigenically and classified epidemiologically as either epizootic or enzootic. Plaque sizes for 148 of these strains were determined, and the pH requirements for hemagglutination (HA) of goose erythrocytes of 131 were studied. Only antigenic variant group IABC strains could be classified epidemiologically as epizootic. In vitro these strains were characterized by the formation of small plaques in Vero cells and a relatively narrow pH range for optimum HA reactivity. Experimental studies in horses confirmed the fact that only IABC strains have epizootic potential. We concluded that plaque size in Vero cell monolayers would be a useful method of screening VEE viruses for equine virulent strains. Indirect evidence suggested that small plaques resulted from sensitivity to an anionic substance present in the agar overlay medium.

In late June 1973, a small outbreak of equine encephalitis caused by eastern equine encephalomyelitis (EEE) virus occurred in the Republic of Panama. At least 100 horses were affected by the disease and 40 died. More than 1,700 human sera were obtained from areas of virus activity but no serological evidence for infection was found. Four isolates of EEE virus were recovered, one of which was from a small pool of Culex taeniopus mosquitoes. Serologic studies of infected horses and classification by the short incubation hemagglutination-inhibition tests revealed that these isolates were South American strains. Our evidence suggests that another agent virulent for horses was active during this outbreak.

Over the past 20 years, obesity has represented a significant focus of research conducted in Clinical Research Centers (CRCs) in the United States. This review will focus on the progress in our understanding of the disease that CRC-based research has produced; therefore, the reference list is not exhaustive and consists primarily of CRC-based research. Obesity is defined as an excess of body fat as measured by triceps skinfold thickness. The time of onset of obesity is an important factor; for example, early onset is associated with an increase in the number of fat cells. Weight loss reduces the size but not the number of fat cells. Type II diabetes mellitus is a common complication in obese adults; this condition has been related to fat cell size and, in women, to predominantly upper-body fat distribution. Pregnant obese women and their babies are at risk for a number of problems. Abnormalities commonly found in obese persons include increased plasma lipid levels, hyperinsulinism, increased cholesterol synthesis, high frequency of gallstones, and hypertension. Under a variety of experimental conditions, the only difference in the response of obese and normal weight subjects to food was that the obese subjects appeared to consume more, but other data suggest that the obese may have greater energy needs. Carbohydrate intake has been studied extensively. Metabolic rate increases with over-feeding, especially in response to carbohydrate. Basal metabolic rates are higher in obese adults and rise in response to overfeeding; they decrease after weight reduction. This decrease can be counteracted with sucrose, perhaps because sucrose maintains triiodothyronine levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Records of the dietary intake of 52 preschool vegetarian children seen from 1974 to 1976 revealed that macrobiotic vegetarian diets provided amounts of vitamin D, calcium, and phosphorus that were marginal as well as less than the amounts provided by other vegetarian diets. Vitamin D supplements were rarely given. Two subjects had roentgenographic evidence of rickets. The medical histories of 32 children on macrobiotic diets who were examined in 1977 more frequently included prior physical and roentgenographic findings indicative of rickets, whereas those of 17 other vegetarian children did not. Children in the former group were more likely to have elevated levels of serum alkaline phosphatase. Two additional cases of rickets in children consuming a macrobiotic diet confirmed by roentgenograms were brought to our attention during the study.

We assessed the nutritional status of 90 pygmies (Efe) and 211 members of a neighboring horticultural Lese in the Ituri forest in northeast Zaire. Clinical signs of iron and iodine deficiency were highly prevalent, but the frequency of these and other clinical signs of nutritional deficiency did not differ between the two groups. Infectious diseases such as yaws, cellulitis, and filiariasis were common. Absolute heights and weights of both Efe males and females aged 2-18 years were less than the 5th percentile of the National Center for Health Statistics standards. Weights for height of both groups were within the normal range. Weights and heights, expressed as percentages of the 50th percentile for age and sex, were significantly lower (P less than .001) in Efe males and females than among Lese males and females, but weights for height did not differ significantly. Z-Scores of height and weight were also significantly lower in Efe males and females than among their Lese counterparts. The differences in weight and height, expressed either as a percentage of the 50th percentile or as Z-scores, were most apparent in older adolescents and persisted among adults. The normal weight for height among both populations indicated that acute undernutrition did not exist at the time of the survey. Despite comparable levels of adult fatness, measured by triceps skinfold thickness, heights of Efe males and females were lower than those of the Lese. These observations support the hypothesis that genetic differences account for the short stature of the Ituri pygmy. However, because the environments shared by the two groups are not identical and because other practices differ, nutritional effects cannot be excluded.

Data from four national surveys indicate pronounced increases in the prevalence of pediatric obesity in the United States. Obese children are defined as those with triceps skinfolds greater than or equal to the 85th percentile of children of the same age and sex in 1963 to 1970. Superobese children are those with skinfolds greater than or equal to the 95th percentile. Compared with skinfold data from the 1963 to 1965 National Health Examination Survey, cycle 2, skinfold data from the second National Health and Nutrition Examination Survey, conducted from 1976 to 1980, indicate a 54% increase in the prevalence of obesity among children 6 to 11 years old and a 98% increase in the prevalence of superobesity. Compared with skinfold data from the 1966 to 1970 National Health Examination Survey, cycle 3, skinfold data from the second National Health and Nutrition Examination Survey indicate a 39% increase in the prevalence of obesity among children 12 to 17 years old and a 64% increase in the prevalence of superobesity. Increases occurred among children of all ages and both sexes and for both blacks and whites. Blood pressure data from the four surveys suggest that the share of pediatric hypertension associated with obesity has increased. Such rapid increases in obesity indicate that environmental causes are likely responsible.

We studied the interrelationship of nitrogen balance (N-bal) and rates of glucose appearance (Ra), determined isotopically using U-13C-glucose, in 14 obese adolescents consuming either (1.5 g protein and 1.0 g glucose)/kg ideal body weight/day or an isonitrogenous diet made isocaloric with fat. Nitrogen balance was significantly (p less than .01) more positive with added glucose. Changes in plasma insulin, free fatty acids, or beta-hydroxybutyrate did not reliably predict N-bal. The Ra of glucose decreased significantly on both diets, but was significantly lower (p less than .001) after the addition of fat. A significant correlation of N-bal with Ra (r = 0.70, p less than .01) was observed only in the absence of dietary glucose. Insulin levels correlated with N-bal only in the presence of dietary glucose (r = 0.72, p less than .01). Nitrogen balance in the absence of dietary carbohydrate may be a consequence of net peripheral protein catabolism that is not directly mediated by the need for gluconeogenic precursors.

Height velocities prior to and during weight reduction were determined retrospectively in 19 obese children selected because of a 10% or greater fall in weight for height. Mean duration of the weight reduction period was 9.7 months. All children were treated with a balanced calorie-deficit diet containing 1.5 to 2.0 g of protein per kilogram of ideal body weight per day. Height velocities were normalized by calculating the Z score for each one. Prior to weight reduction, the mean (+/- SD) Z score for height velocity was 2.32 +/- 2.47 units. Eleven patients were 2 SDs or more above the mean height velocity for age and sex. During weight reduction, the mean Z score for height velocity decreased significantly to 0.62 +/- 2.37 units. The change in Z score before and during weight reduction was significantly correlated with the change in weight but not with the change in weight for height. These data indicate that even mildly restrictive diets may be associated with a reduction in linear growth velocity. The implications of these observations for the risk of other adverse consequences of weight reduction are not clear. Nonetheless, our observations emphasize the importance of careful monitoring of obese children during mildly restrictive dietary therapy.

The identification of obesity as a pathological diagnosis depends on an accurate assessment of body fatness and a correlation of fatness with pathological consequences. Because total body fat varies with body weight, the proportion of body weight that is fat is probably a more reliable indicator of risk. Among obese children and adolescents, several problems have hindered the development of accurate clinical measures of percent body fat and total body fat. First, the use of direct methods to measure body composition is limited by expense and labor. Second, the relationship between anthropometric indexes and body composition in obese children and adolescents has not been intensively studied. Third, sample sizes of normal weight children have been too small to permit the development of diagnostic criteria. Fourth, the triceps skinfold is less reproducible in overweight subjects. Increases in lean body mass in obese adolescents may confound the use of the body mass index as a measure of adiposity. Current laboratory methods for the measurement of body composition include: (1) underwater weighing, (2) 40K counting, (3) isotopic dilution measures, (4) neutron activation, and (5) electrical impedance. This article examines relationships between those methods and anthropometry in the measurement of fatness in children and adolescents, as well as the difficulties in measuring body fatness and the importance of body fat distribution and its relationship to morbidity in children. Current evidence suggests an association of morbidity and upper segment obesity in adults. Corresponding studies in children and adolescents are yet to be carried out.

The association of television viewing and obesity in data collected during cycles II and III of the National Health Examination Survey was examined. Cycle II examined 6,965 children aged 6 to 11 years and cycle III examined 6,671 children aged 12 to 17 years. Included in the cycle III sample were 2,153 subjects previously studied during cycle II. These surveys, therefore, provided two cross-sectional samples and one prospective sample. In all three samples, significant associations of the time spent watching television and the prevalence of obesity were observed. In 12- to 17-year-old adolescents, the prevalence of obesity increased by 2% for each additional hour of television viewed. The associations persisted when controlled for prior obesity, region, season, population density, race, socioeconomic class, and a variety of other family variables. The consistency, temporal sequence, strength, and specificity of the associations suggest that television viewing may cause obesity in at least some children and adolescents. The potential effects of obesity on activity and the consumption of calorically dense foods are consistent with this hypothesis.

A 6-month-old girl developed intermittent dystonic posture of the legs and eczematous dermatitis without ataxia. Qualitative and quantitative urine amino acid testing confirmed the diagnosis of Hartnup disease. Cranial computed tomography, electroencephalogram, electromyogram/nerve conduction study, posterior tibial somatosensory evoked potentials, 24-hour electroencephalographic telemetry, and metrizamide myelogram were normal. Spinal fluid hydroxy-indoleacetic acid concentration was less than or equal to 2 S.D. of normal; oral tryptophan loading (70 mg/kg) resulted in a two-fold rise in cerebrospinal fluid 5-hydroxy-indoleacetic acid concentration. Tryptophan administered alone or with nicotinic acid failed to improve the dystonia; however, trihexyphenidyl (1-2 mg/kg/day) dramatically improved it. Hartnup disease should be considered in children with unexplained dystonia.

Thirty-nine preschool children consuming different types of vegetarian diets were studied. Type and amount of carbohydrate, fat, protein, and amount of sodium and cholesterol provided by their diets were more like intakes suggested in the proposed Dietary Goals for the United States than to levels in usual diets of nonvegetarian children. Macrobiotic vegetarian children consumed less animal food than did other vegetarian children. The mean intake of vitamin D of macrobiotics was an eighth of the Recommended Dietary Allowance and mean serum alkaline phosphatase values were elevated. The mean intake of vitamin B12 levels were normal. Vegan macrobiotic children had the lowest intakes of vitamins B12 and D. Other vegetarians' mean intakes of these vitamins met the Recommended Dietary Allowance. Mean iron intakes of the vegetarians approximated the Recommended Dietary Allowance. Hematological indices were suggestive of mild iron deficiency anemia in a quarter of subjects. Serum cholesterol values were low for the group. Physical measurements were within normal limits and macrobiotic vegetarians were not smaller or leaner than other vegetarian children. The nutritional difficulties discovered could be corrected by careful planning of vegetarian children's diets while preserving the beneficial qualities of the diet in other respects.

Many of the metabolic and gastrointestinal complications that occur when patients receive tube feedings result from improper selection or administration of the formula. An algorithm, available tables of formula composition, and adequate flowsheets for recording clinical information that can be adapted to individual institutions will provide simple and practical guidelines for the selection, administration, and management of enteral feeding programs in pediatric patients.

The increasing prevalence of childhood obesity, its attendant morbidity, and the limited success of therapy mandate increased attention to preventive approaches. Environmental and family variables serve to identify families with children at risk for the development of obesity. Although the behavioral correlates that link these risk factors to childhood obesity remain unclear, inactivity and increased dietary intake of fat appear at this time to be the most logical foci for preventive interventions. Television viewing, which promotes both increased food consumption and reduced activity, represents a major concern at which counseling should be directed.