Television watching, energy intake, and obesity in US children: results from the third National Health and Nutrition Examination Survey, 1988-1994

OBJECTIVES: To examine the relationship between television watching, energy intake, physical activity, and obesity status in US boys and girls, aged 8 to 16 years. METHODS: We used a nationally representative cross-sectional survey with an in-person interview and a medical examination, which included measurements of height and weight, daily hours of television watching, weekly participation in physical activity, and a dietary interview. Between 1988 and 1994, the Third National Health and Nutrition Examination Survey collected data on 4069 children. Mexican Americans and non-Hispanic blacks were oversampled to produce reliable estimates for these groups. RESULTS: The prevalence of obesity is lowest among children watching 1 or fewer hours of television a day, and highest among those watching 4 or more hours of television a day. Girls engaged in less physical activity and consumed fewer joules per day than boys. A higher percentage of non-Hispanic white boys reported participating in physical activity 5 or more times per week than any other race/ethnic and sex group. Television watching was positively associated with obesity among girls, even after controlling for age, race/ethnicity, family income, weekly physical activity, and energy intake. CONCLUSIONS: As the prevalence of overweight increases, the need to reduce sedentary behaviors and to promote a more active lifestyle becomes essential. Clinicians and public health interventionists should encourage active lifestyles to balance the energy intake of children.     

Decreasing sedentary behaviors in treating pediatric obesity

BACKGROUND: Epidemiological studies have shown television watching to be a risk factor for the development of obesity in children. The effect of reducing television watching and other sedentary behaviors as a component of a comprehensive obesity treatment program has not been thoroughly tested. OBJECTIVE: To compare the influence of targeting decreases in sedentary behavior vs. increases in physical activity in the comprehensive treatment of obesity in 8- to 12-year-old children. DESIGN: Randomized, controlled outcome study. SETTING: Childhood obesity research clinic. DESIGN: Ninety families with obese 8- to 12-year-old children were randomly assigned to groups that were provided a comprehensive family-based behavioral weight control program that included dietary, and behavior change information but differed in whether sedentary or physically active behaviors were targeted and the degree of behavior change required. RESULTS: Results during 2 years showed that targeting either decreased sedentary behaviors or increased physical activity was associated with significant decreases in percent overweight and body fat and improved aerobic fitness. Self-reported activity minutes increased and targeted sedentary time decreased during treatment. Children substituted nontargeted sedentary behaviors for some of their targeted sedentary behaviors. CONCLUSION: These results support reducing sedentary behaviors as an adjunct in the treatment of pediatric obesity.     

Childhood obesity: trends and potential causes

The increase in childhood obesity over the past several decades, together with the associated health problems and costs, is raising grave concern among health care professionals, policy experts, children's advocates, and parents. Patricia Anderson and Kristin Butcher document trends in children's obesity and examine the possible underlying causes of the obesity epidemic. They begin by reviewing research on energy intake, energy expenditure, and "energy balance," noting that children who eat more "empty calories" and expend fewer calories through physical activity are more likely to be obese than other children. Next they ask what has changed in children's environment over the past three decades to upset this energy balance equation. In particular, they examine changes in the food market, in the built environment, in schools and child care settings, and in the role of parents-paying attention to the timing of these changes. Among the changes that affect children's energy intake are the increasing availability of energy-dense, high-calorie foods and drinks through schools. Changes in the family, particularly an increase in dual-career or single-parent working families, may also have increased demand for food away from home or pre-prepared foods. A host of factors have also contributed to reductions in energy expenditure. In particular, children today seem less likely to walk to school and to be traveling more in cars than they were during the early 1970s, perhaps because of changes in the built environment. Finally, children spend more time viewing television and using computers. Anderson and Butcher find no one factor that has led to increases in children's obesity. Rather, many complementary changes have simultaneously increased children's energy intake and decreased their energy expenditure. The challenge in formulating policies to address children's obesity is to learn how best to change the environment that affects children's energy balance.     

Psychosocial correlates of physical activity in healthy children

BACKGROUND: Understanding the determinants of physical activity in children is critical for the treatment and prevention of childhood obesity. Social-cognitive theory has been used to understand behavioral patterns in children. OBJECTIVES: To explore the relationship between health beliefs, self-efficacy, social support, and sedentary activities and physical activity levels in children and to examine the relationship between physical activity and children's self-esteem. METHODS: Ninety-two children aged 10 to 16 years completed the study. Physical activity was monitored for 1 week with a motion detector (Actitrac; IM Systems, Baltimore, Md). Moderate-level activity and high-level activity were defined based on the results of treadmill testing. Health beliefs, self-efficacy, social influences, and time spent in sedentary behaviors were determined through questionnaires. Self-esteem was measured using the Piers-Harris Children's Self-Concept Scale. Chronic anxiety was measured with the Revised Children's Manifest Anxiety Scale. RESULTS: There was a significant decline in physical activity levels between ages 10 and 16 years, particularly in girls. Preteen girls spent approximately 35% more time in low- and high-level activity than did teenage girls (P<.001). Overall, children spent 75.5% of the day inactive, with a mean +/- SD of 5.2 +/- 1.8 hours watching television, sitting at the computer, and doing homework. In contrast, only 1.4% of the day (12.6 +/- 12.2 minutes) was spent in vigorous activity. Time spent in sedentary behaviors was inversely correlated with the amount of moderate-level activity (P<.001) but not high-level activity. In contrast, time spent in high-level activity correlated with self-efficacy scores (P<.001) and social influences scores (P<.005). High-level physical activity was also associated with improved self-esteem (P<.05). Higher health beliefs scores were not correlated with physical activity levels. CONCLUSIONS: Children and adolescents are largely sedentary. Correlates of high- and low-level physical activity are different. Time spent on sedentary activities is inversely correlated with moderate-level activity, while self-efficacy and social influences are positively correlated with more intense physical activity. In addition, increased high-level physical activity is an important component in the development of self-esteem in children.     

Energy balance: an overview with emphasis on children

Childhood obesity is a significant public health problem, affecting one in five children in the United States. At the crux of this issue is a dysregulation of energy intake and energy expenditure. This review will provide an overview on energy and nutrient balance. We discuss energy balance studies in children using indirect and direct measures, and focus particularly on obesity as a deleterious consequence in childhood survivors of cancer. Obesity affects 11-57% of children with acute lymphoblastic leukemia, probably due to increased energy intake and reduced energy expenditure secondary to reduced habitual activity caused by fatigue. However, most of the studies in children with leukemia are retrospective, use BMI as a measure of obesity, and are inconclusive about the impact of the type of treatment on the development of obesity later in life. To better understand the etiology of obesity in both healthy and sick children, we need to undertake nutrient balance studies with appropriate measures of fat mass and fat distribution while keeping in mind the influence of normal tissue growth and puberty on energy balance.     

Childhood obesity: Pathophysiology and treatment

Childhood obesity is among the most difficult problems which pediatricians treat. It is frequently ignored by the pediatrician or viewed as a form of social deviancy, and blame for treatment failure placed on the patients or their families. The definition of obesity is difficult. Using total body electrical conductivity (TOBEC) technology, total body fat ranges between 12% and 30% of total body weight in normal children and adolescents. This is influenced not only by age, but also by physical fitness. Anthropometry is the easiest way to define obesity. Children whose weight exceeds 120% of that expected for their height are considered overweight. Skinfold thickness and body mass index are indices of obesity that are more difficult to apply to the child. Childhood obesity is associated with obese parents, a higher socioeconomic status, increased parental education, small family size and a sedentary lifestyle. Genetics also clearly plays a role. Studies have demonstrated that obese and non-obese individuals have similar energy intakes implying that obesity results from very small imbalances of energy intake and expenditure. An excess intake of only 418 kJ per day can result in about 4.5 kg of excess weight gain per year. Small differences in basal metabolic rate or the thermic effects of food may also account for the difference in energy balance between the obese and non-obese. In the Prader Willi Syndrome, there appears to be a link between appetite and body fatness. When placed on growth hormone, lean body mass increases, body fat decreases, sometimes to normal, and appetite becomes more normal. Our weight control program is very intensive and combines behavior modification with dietary instruction and exercise. Patients are screened both physically and psychologically. Abnormalities found are treated before the child is allowed to enter the weight loss program. Depression is frequently encountered. If treatment success is defined as either weight reduction or maintenance of weight as linear growth increases, then 88% of the children who completed the program were successful. The dropout rate however was 65%.     

Effect of socioeconomic status on objectively measured physical activity.

BACKGROUND: A socioeconomic gradient in childhood obesity is known to be present by the age of school entry in the UK. The origin of this gradient is unclear at present, but must lie in socioeconomic differences in habitual physical activity, sedentary behaviour, or dietary intake. AIMS: To test the hypothesis that habitual physical activity and/or sedentary behaviour are associated with socioeconomic status (SES) in young Scottish children. METHODS: Observational study of 339 children (mean age 4.2 years, SD 0.3) in which habitual physical activity and sedentary behaviour were measured by accelerometry over six days (study 1). In a second study, 39 pairs of children of distinctly different SES (mean age 5.6 years, SD 0.3) were tested for differences in habitual physical activity and sedentary behaviour by accelerometry over seven days. RESULTS: In study 1, SES was not a significant factor in explaining the amount of time spent in physical activity or sedentary behaviour once gender and month of measurement were taken into account. In study 2, there were no significant differences in time spent in physical activity or sedentary behaviour between affluent and deprived groups. CONCLUSION: Results do not support the hypothesis that low SES in young Scottish children is associated with lower habitual physical activity or higher engagement in sedentary behaviour.     

Longitudinal stability of sedentary behaviors and physical activity during early adolescence

The purpose of this study was to examine the stability of sedentary behaviors and physical activity in Estonian school children aged 11-12 year at the beginning of the study. In addition, the consequence of changes in sedentary behaviors on a change in physical activity was investigated. Adolescents (N = 345) completed the 3-Day Physical Activity Recall on four occasions over a 22-month period. Results indicated the curvilinear changes in sedentary behaviors and physical activity across time. There was a significant decrease in physical activity and an increase in sedentary behaviors across three years. Stability coefficients indicated a moderate differential stability of the sedentary behaviors (ranged from 0.31 to 0.64) and physical activity (ranged from 0.36 to 0.59) during early adolescence. Latent growth modeling indicated that increase in sedentary behaviors across a 22-month period was inversely associated with a change in physical activity. Interventions targeted at "high-risk" groups to reduce sedentary behaviors during early adolescence are encouraged.     

Association of energy intake and expenditure with obesity: A cross-sectional study of 150 pediatric patients following treatment for leukemia

Increased obesity in leukemia survivors has been attributed to chemotherapy and radiation. Data on total energy intake (TEI) and total energy expenditure (TEE) are lacking in obese childhood leukemia patients after completion of therapy from India. We conducted a cross-sectional study in pediatric acute leukemia patients after completion of therapy wherein energy intake was assessed by 24-hour recall method. TEE was calculated using Harris–Benedict equation, by assessing the physical activity level using Physical Activity Questionnaire for children and basal metabolic rate by World Health Organization equation. Indian Academy of Pediatrics 2015 guidelines for BMI were used for defining overweight and obesity. Nutritional status was assessed in 150 leukemia patients after completion of therapy. Twenty-five percent of leukemia patients after completion of therapy were overweight and obese versus 11% of healthy controls (p = 0.042). The mean ratio of TEI/required energy intake (REI), TEE/required energy expenditure (REE), and (TEI:REI)/(TEE:REE) were significantly higher in overweight and obese group versus nonobese survivors (p < 0.001, p = 0.091, p < 0.001, respectively). Multivariate analysis showed higher income (HR-2.3, p = 0.04), increased TEI/REI (HR-4, p = 0.049) and higher (TEI:REI)/(TEE:REE) (HR-3.1, p = 0.039) to be significant factors predicting obesity. Obesity in leukemia patients after completion of therapy is associated with increased energy intake, causing imbalance between energy intake and TEE in these patients.     

Dietary and Physical Activity Behaviors of New York City Children From Different Ethnic Minority Subgroups

ObjectiveTo examine racial/ethnic differences in diet and physical activity behaviors in ethnic minority New York City children.MethodsCross-sectional data from a community-based study of 486 6- to 8-year-old children were used. Race/ethnicity was derived using a caregiver's report of child's race and Hispanic ancestry. Dietary intake was obtained by 24-hour diet recalls using the Nutrition Data System for Research. Physical activity was assessed with pedometers and caregiver interviews. We compared diet and activity measures across racial/ethnic subgroups using chi-square and analysis of variance tests. Multivariate analyses adjusted for age, gender, body mass index, and caregiver education (with breastfeeding history and total energy intake included in diet models).ResultsParticipants (N = 486) were categorized as Mexican (29.4%), Dominican (8.4%), Puerto Rican (20.6%), other/mixed Hispanic (14.0%), or non-Hispanic black (27.6%). Obesity rates were lower in non-Hispanic blacks (18%) than in Hispanics (31%). Mexicans had the lowest obesity rates among Hispanic subgroups (25%), and Dominicans had the highest (39%). There were differences in mean daily servings of food groups, with Mexicans having healthier diets and Puerto Ricans and non-Hispanic Blacks having less healthy diets. Sedentary time was lower in Mexicans than in other groups in adjusted models. Examination of additional models, including home language, did not show significant differences in the estimates.ConclusionDiet and activity behaviors varied across racial/ethnic subgroups. Specifically, Mexican children had healthier diets, the least amount of sedentary time, and the lowest rates of obesity among the Hispanic subgroups examined. Targeted interventions in ethnic subgroups may be warranted to address specific behaviors.     

Energy balance, physical activity, and thermogenic effect of feeding in premature infants

In order to assess the contribution of the thermogenic effect of feeding and muscular activity to total energy expenditure, nine premature infants were studied for 2 consecutive days during which time repeated measurements of energy expenditure by indirect calorimetry were performed throughout the day, combined with a visual activity score based on body movement. The infants were growing at 16.6 +/- 4.0 g/kg/day (mean +/- SD) and received 110 +/- 8 kcal/kg/day metabolizable energy (milk formula) and 522 +/- 40 mgN/kg/day. Their total energy expenditure was 68 +/- 4 kcal/kg/day indicating that 41 +/- 7 kcal/kg/day was retained for growth. Based on the combination of energy + N balances it was estimated that 80% of the weight gain was fat-free tissue and 20% was fat tissue. The rate of energy expenditure measured minute-by-minute was significantly and linearly correlated with the activity score in both the premeal (r = 0.75;p less than 0.001) and the postmeal periods (r = 0.74; p less than 0.001) with no difference in the regression slope, but with a significant difference in intercept. In preset feeding schedules the latter allowed an estimation of the thermogenic effect without the confounding effect of activity. This was found to be 3.1 +/- 1.8% when expressed as a percentage of metabolizable energy intake. However when the "classical" approach was used as a comparison (integration of extra energy expenditure induced by the meal), the thermogenic effect was found to be greater, i.e. 9.5 +/- 3.8% of the meal's metabolizable energy, due to the superimposed effect of physical activity in the postprandial state.(ABSTRACT TRUNCATED AT 250 WORDS)     

Resting energy expenditure and body composition in children with myelomeningocele

PURPOSE: Myelomeningocele is a complex disease often complicated by obesity for reasons not well understood. The objectives of this study were to determine body composition and energy expenditure of children with MMC. METHODS: Resting energy expenditure (REE), body composition and anthropometry were measured in 19 children with MMC (12 M, 7 F). Total energy expenditure (TEE) was estimated using a 3-day activity record. Energy intake (EI) was measured in seven children (5 M, 2 F) with MMC. Data were then compared with predicted values. RESULTS: Mean REE (n = 19) was 4680 +/- 1452 kJ/day (96.1 +/- 18.1% of predicted REE). The range was large (45.8-125.7% of predicted REE). TEE (n = 7) was 4344 +/- 2376 kJ/day, hence only 73 34% of predicted TEE. EI (n = 7) was 6560 +/- 1329 kJ/day, approximating a normal energy requirement. Overall, BCM was lower than expected values. CONCLUSIONS: REE in children with MMC is variable when compared to predicted values. TEE was found to be lower in children with MMC than predicted values and EI was similar to predicted values in this group of seven children. BCM is reduced in children with MMC when compared to expected values.     

The 'skinny' on childhood obesity: how our western environment starves kids' brains

In this review, the mechanism of our "toxic environment's" effects on insulin and weight gain in the genesis of obesity is elaborated. The composition of our diet is highly insulinogenic. The insulin drives energy into fat, and interferes with leptin signaling in the VMH. This results in weight gain and the sense of starvation, which results in decreased SNS activity, reducing energy expenditure and physical activity; and increased vagal activity, which promotes yet further insulin release and energy storage. Thus, hyperinsulinemia turns the leptin negative feedback system into a "vicious cycle" of obesity (see Figure 3, page 905). Externally, this appears as "gluttony and sloth" but it is biochemically driven. How does this work? A thin, insulin-sensitive, 13-year-old boy might consume a daily allotment of 2,000 kcal, and burn 2,000 kcal daily (or 50 kcal/kg fat-free mass) in order to remain weight-stable, with a stable leptin level. However, if that same 13-year-old became hyperinsulinemic and/or insulin resistant, perhaps as many as 250 kcal of the daily allotment would be shunted to storage in adipose tissue, promoting a persistent obligate weight gain. Due to the obligate energy storage, he now only has 1,750 kcal per day to burn. The hyperinsulinemia also results in a lower level of leptin signal transduction, conveying a CNS signal of energy insufficiency. The remaining calories available are lower than his energy expenditure; the CNS would sense starvation. Through decreased SNS tone, he would reduce his physical activity, resulting in decreased quality of life; and through increased vagal tone, he would increase caloric intake and insulin secretion, but now at a much higher level. Thus, the vicious cycle of gluttony, sloth, and obesity is promulgated. Is this personal responsibility, when a kid's brain thinks it's starving? Is it personal responsibility when the American Academy of Pediatrics still recommends juice for toddlers? Is it personal responsibility when the Women, Infant and Children program subsidizes fruit juice but not fruit? Is it personal responsibility when the first ingredient in the barbecue sauce is high-fructose corn syrup? Is it personal responsibility when high-fiber fresh produce is unavailable in poor neighborhoods? Is it personal responsibility when the local fast food restaurant is the only neighborhood venue that is clean and air-conditioned? Is it personal responsibility when in order to meet the criteria for No Child Left Behind, the school does away with physical education class? Is it personal responsibility when children are not allowed out of the house to play for fear of crime? We must get the insulin down. Fixing the "toxic environment" by altering the food supply and promoting physical activity for all children can't be done by government, and won't be done by Big Food. This will require a grassroots, bottom-up effort on the part of parents and community leaders. We as pediatricians must lead the way.     

Determining factors of physical activity level in school children and adolescents: the OPACA study

IntroductionPhysical activity is a key factor for human health. This study attempts to measure the level of physical activity in children and to find out what are the factors that determine it.MethodIn a sample of the 11 and 14 year-old population of the centre-south area of Palencia, physical activity was measured using a three day diary, and anthropometric and socioeconomic variables were collected. Three variables were analysed: fat-free mass adjusted activity energy expenditure (AEE/FFM), physical activity level (PAL), and categorical physical activity (active/inactive).ResultsA total of 179 children were included, of whom 71.5% were active or very active. Males were more active than females, and activity was also higher in summer. Physical activity declined between 11 and 14 years, and was lower during the weekends than in working days. There were no differences related to obesity, overweight or percent body fat. More active children had lower blood pressure. Physical activity was directly related to weekly hours spent in sport activities, and inversely related to time spent on sedentary activities. Multivariate analysis showed that children from families with low educational levels had a higher activity level not related to sport activities.ConclusionsThe level of physical activity in this population is acceptable, although there are sex differences and there is a declining trend through the adolescence.     

Elite premenarcheal rhythmic gymnasts demonstrate energy and dietary intake deficiencies during periods of intense training

This study determined dietary intake and energy balance of elite premenarcheal rhythmic gymnasts during their preseason training. Forty rhythmic gymnasts and 40 sedentary age-matched females (10-12 yrs) participated in the study. Anthropometric profile and skeletal ages were determined. Dietary intake and physical activity were assessed to estimate daily energy intake, daily energy expenditure, and resting metabolic rate. Groups demonstrated comparable height, bone age, pubertal development, resting metabolic rate. Gymnasts had lower body mass, BMI, body fat than age-matched controls. Although groups demonstrated comparable daily energy intake, gymnasts exhibited a higher daily energy expenditure resulting in a daily energy deficit. Gymnasts also had higher carbohydrate intake but lower fat and calcium intake. Both groups were below the recommended dietary allowances for fiber, water, calcium, phosphorus and vitamin intake. Gymnasts may need to raise their daily energy intake to avoid the energy deficit during periods of intense training.     

Longitudinal study of energy expenditure in preterm neonates <30 weeks' gestation during the first three postnatal weeks

OBJECTIVES: The objective of this study was to measure energy expenditure (EE) in a contemporary population of preterm neonates <30 weeks' gestation. STUDY DESIGN: Prospective longitudinal cohort study in 26 consecutive preterm neonates (gestational age, 27 weeks [23-29] [median, range]; birth weight, 980 g [554-1592]). EE was measured by indirect calorimetry on postnatal days 1, 3, 5, 10, and 21. Data on body weight, energy intake, and medical therapy were prospectively collected. RESULTS: EE increased from 121 +/- 25 kJ/kg per day (29 +/- 6 kcal/kg per day) (mean +/- SD) on day 1 to 222 +/- 25 kJ/kg per day (53 +/- 6 kcal/kg per day) on day 21. An energy deficit occurred only on day 1. EE was closely related to energy intake: For each additional kJ given, EE increased by 0.3 kJ (r = 0.789, P <.0001). Neonates with a birth weight <1000 g did not have a more pronounced energy deficit than the heavier neonates. EE during nasal continuous positive airway pressure in the first postnatal week was 25% lower than during spontaneous respiration. CONCLUSIONS: EE could be predicted from energy intake with acceptable accuracy in preterm neonates <30 weeks' gestation during the first 3 postnatal weeks. There was no prolonged energy deficit.     

Pathophysiologic basis for growth failure in children with ichthyosis: an evaluation of cutaneous ultrastructure, epidermal permeability barrier function, and energy expenditure

OBJECTIVE: Because an impaired epidermal permeability barrier is present in many of the ichthyoses, we examined the contribution of barrier failure to caloric requirements in children with ichthyosis and growth failure. STUDY DESIGN: Transepidermal water loss (TEWL) and ultrastructural parameters of the permeability barrier were evaluated in 10 hospitalized children with ichthyosis and growth failure. Nutritional intake, resting energy expenditure, and calories lost as heat of evaporation were determined. RESULTS: Mean basal TEWL rates were markedly elevated in all study patients in comparison to the expected upper limit of normal (39.6+/-20.6 vs 8.7 mL/m(2) per hour). The severity of abnormalities in the ultrastructure of permeability barrier-related structures, assessed semiquantitatively, correlated significantly to mean basal TEWL rates (P <.001). Total body daily TEWL was elevated (746 +/- 468 vs 209 mL/d), resulting in a caloric drain of 433 +/- 272 kcal/d (21 +/- 9.8 kcal/kg per day) through heat of evaporation. Nutrient intake exceeded requirements in all, but resting energy expenditure exceeded predicted in 5 of 6 patients and correlated significantly with mean basal TEWL rates (P <.005). CONCLUSIONS: A defective permeability barrier in children with ichthyosis can result in ample chronic losses of water and calories to impair growth.     

Ghrelin--an indicator for fat oxidation in obese children and adolescents during a weight reduction program

The aim of this study was to investigate the effect of short-term energy restriction combined with physical activity on changes in substrate oxidation and changes in plasma concentrations of ghrelin. We designed a longitudinal intervention study of 4.2 MJ (= 1,000 kcal) daily with exercise. Eighteen obese children and adolescents (age: 13.1 +/- 1.6 years, 13 girls, 5 boys, 17 White, 1 Black) participated. We measured body mass index (BMI), plasma ghrelin, resting energy expenditure (REE), VCO2, VO2 and respiratory quotient (RQ) at baseline and after 10 days. There was a significant decrease of BMI during the 10 day program (28.6 +/- 4.3 vs 27.5 +/- 4.2; p < 0.001). Ghrelin and RQ showed a tendency to increase, but the difference did not reach significance (ghrelin: 83.4 +/- 37.1 vs 99.5 +/- 41.2, p = 0067; RQ: 0.83 +/- 0.06 vs 0.85 +/- 0.08, p = 0.433). The changes in RQ were significantly and independently correlated with the changes in plasma ghrelin (p = 0.029). The increase in RQ suggests a shift from fat oxidation towards carbohydrate oxidation. Ghrelin reflects the same sensitivity as RQ to changes in energy balance. Therefore, ghrelin seems to be a sensitive indicator for changes in substrate oxidation.     

Daily physical activity related to body fat in children aged 8-11 years

OBJECTIVE: To evaluate the association between objectively measured daily physical activity and body fat. STUDY DESIGN: Cross-sectional, observational, study of 248 children aged 7.9 to 11.1 years. Abdominal fat mass and total body fat mass were measured by dual-energy X-ray absorptiometry. Daily physical activity was assessed by accelerometers for 4 days. RESULTS: Total body fat expressed as a percentage of body mass was inversely related to minutes of vigorous physical activity per day, for all children r = -0.38 (P < .05). Children, both boys and girls, in the highest quartile of body fat performed on average 12 minutes less vigorous activity per day compared with their counterparts in the lowest quartile. Multiple regression analysis revealed that independent factors for body fat were number of minutes of vigorous activity per day and sex. CONCLUSION: Low physical activity can be a contributing factor in childhood obesity. Only longitudinal studies, however, can give more definitive information about the relation between daily physical activity and obesity.     

Daily metabolic rate in healthy infants

BACKGROUND: Previous estimates of daily metabolic rate in infants were based on short-term unstandardized measurements of energy expenditure (EE). OBJECTIVE: Determine 24-hour metabolic profiles in infants. METHODS: Energy expenditure (kcal/min by indirect calorimetry) and physical activity (oscillations in weight/min/kg body weight) were measured in 10 healthy infants (5.0+/-0.8 months, 68+/-3 cm, 7.3+/-0.8 kg) for 24 hours in the Enhanced Metabolic Testing Activity Chamber while allowing parental interaction. Energy intake, 24-hour EE, resting metabolic rate (RMR), and sleeping metabolic rate (SMR) (kcal/kg/day) were determined. In addition, extrapolated 24-hour EE, RMR, and SMR from the first 4 and 6 hours of data were compared with 24-hour measurements. RESULTS: Twenty-four-hour energy intake, EE, RMR, and SMR (mean+/-SD) were 78.2+/-17.6, 74.7+/-3.8, 65.1+/-3.5, and 60.3+/-3.9, respectively. EE and physical activity showed a decrease at 11:30 pm and a return to daytime levels by 5:30 am, suggesting a metabolic circadian rhythm. Extrapolated 24-hour EE, RMR, and SMR from the first 4 hours (72.2+/-6.6, 65.9+/-8.7, and 64.9+/-6.4) and 6 hours (74.8+/-6.7, 65.8+/-6.6, and 64.8+/-5.6) were similar to 24-hour measurements. CONCLUSIONS: An apparent circadian rhythm in metabolic rate and physical activity was detected by 24-hour measurements. Furthermore, shorter-term measurements of the variables were comparable with 24-hour values.