Toddler physical activity study: laboratory and community studies to evaluate accelerometer validity and correlates.

BACKGROUND: Toddlerhood is an important age for physical activity (PA) promotion to prevent obesity and support a physically active lifestyle throughout childhood. Accurate assessment of PA is needed to determine trends/correlates of PA, time spent in sedentary, light, or moderate-vigorous PA (MVPA), and the effectiveness of PA promotion programs. Due to the limited availability of objective measures that have been validated and evaluated for feasibility in community studies, it is unclear which subgroups of toddlers are at the highest risk for inactivity. Using Actical ankle accelerometry, the objectives of this study are to develop valid thresholds, examine feasibility, and examine demographic/ anthropometric PA correlates of MVPA among toddlers from low-income families. METHODS: Two studies were conducted with toddlers (12-36 months). Laboratory Study (n = 24)- Two Actical accelerometers were placed on the ankle. PA was observed using the Child Activity Rating Scale (CARS, prescribed activities). Analyses included device equivalence reliability (correlation: activity counts of two Acticals), criterion-related validity (correlation: activity counts and CARS ratings), and sensitivity/specificity for thresholds. Community Study (n = 277, low-income mother-toddler dyads recruited)- An Actical was worn on the ankle for > 7 days (goal >5, 24-h days). Height/weight was measured. Mothers reported demographics. Analyses included frequencies (feasibility) and stepwise multiple linear regression (sMLR). RESULTS: Laboratory Study- Acticals demonstrated reliability (r = 0.980) and validity (r = 0.75). Thresholds demonstrated sensitivity (86 %) and specificity (88 %). Community Study- 86 % wore accelerometer, 69 % had valid data (mean = 5.2 days). Primary reasons for missing/invalid data: refusal (14 %) and wear-time ≤2 days (11 %). The MVPA threshold (>2200 cpm) yielded 54 min/day. In sMLR, MVPA was associated with age (older > younger, ß = 32.8, p < 0.001), gender (boys > girls, ß = -11.21, p = 0.032), maternal MVPA (ß = 0.44, p = 0.002) and recruitment location (suburban > urban, ß = 19.6, p < 0.001), or race (non-Black > Black, ß = 18.5, p = 0.001). No association with toddler weight status. CONCLUSIONS: Ankle accelerometry is a valid, reliable, and feasible method of assessing PA in community studies of toddlers from low-income families. Sub-populations of toddlers may be at increased risk for inactivity, including toddlers that are younger, female, Black, those with less active mothers, and those living in an urban location.

Process evaluation and impact results of the worksite component of a multilevel, multicomponent obesity prevention trial in six Native American communities.

Native Americans (NA) have higher obesity rates compared to other populations. Employed adults spend a significant amount of time at work. OPREVENT2, an obesity prevention trial in 6 NA communities, included a worksite component that incorporated nutrition and physical activity educational media, competitions, tastes tests, and coffee station makeovers. Process evaluation results indicate a well-implemented worksite component based on team standards. Statistically significant improvements of coffee stations healthy offerings (p=0.006), but none in health policies and resources, were observed. Partnering with businesses to create healthier working environments was successful and future trials should investigate the effects on an individual level.

Cardiometabolic risk among rural Native American adults in a large multilevel multicomponent intervention trial.

This cross-sectional analysis of the baseline evaluation sample of the Obesity Prevention and Evaluation of InterVention Effectiveness in Native Americans 2 (OPREVENT2) study included 601 Native American adults ages 18-75 living in rural reservation communities in the Midwest and Southwest United States. Participants completed a self-report questionnaire for individual and family history of hypertension, heart disease, diabetes and obestiy. Body mass index (BMI), percent body fat, and blood pressure were measured by trained research staff. About 60% of respondents had a BMI >30 kg/m2. Approximately 80% had a waist-to-hip ratio and percent body fat classified as high risk, and nearly 64% had a high-risk blood pressure measurement. Although a large proportion of participants reported a family history of chronic disease and had measurements that indicated elevated risk, relatively few had a self-reported diagnosis of any chronic disease. Future studies should examine potential connections between healthcare access and discordance in self-reported versus measured disease risks and diagnoses.

Exposure to a Multilevel, Multicomponent Obesity Prevention Intervention (OPREVENT2) in Rural Native American Communities: Variability and Association with Change in Diet Quality.

The OPREVENT2 obesity prevention trial was a multilevel multicomponent (MLMC) intervention implemented in rural Native American communities in the Midwest and Southwest U.S. Intervention components were delivered through local food stores, worksites, schools, community action coalitions, and by social and community media. Due to the complex nature of MLMC intervention trials, it is useful to assess participants' exposure to each component of the intervention in order to assess impact. In this paper, we present a detailed methodology for evaluating participant exposure to MLMC intervention, and we explore how exposure to the OPREVENT2 trial impacted participant diet quality. There were no significant differences in total exposure score by age group, sex, or geographic region, but exposure to sub-components of the intervention differed significantly by age group, sex, and geographical region. Participants with the highest overall exposure scores showed significantly more improvement in diet quality from baseline to follow up compared to those who were least exposed to the intervention. Improved diet quality was also significantly positively associated with several exposure sub-components. While evaluating exposure to an entire MLMC intervention is complex and imperfect, it can provide useful insight into an intervention's impact on key outcome measures, and it can help identify which components of the intervention were most effective.

Associations between patterns of objectively measured physical activity and risk factors for the metabolic syndrome.

PURPOSE: To determine whether certain patterns of objectively measured physical activity (PA) are associated with the risk factors for or the diagnosis of the metabolic syndrome (MS). DESIGN: Latent class analysis, including assessment of the associations between latent PA classes and risk factors for the MS. SETTING: Random sample from throughout the United States using data from the 2003-2004 National Health and Nutrition Examination Survey. SUBJECTS: A total of 3458 civilian adult noninstitutionalized U.S. citizens. MEASURES: Daily minutes of moderate-to-vigorous PA across a 7-day week based on accelerometer measurements, as well as high blood pressure, blood glucose levels, triglyceride levels, and body mass index, along with low levels of high density lipoproteins, using clinical cut points. RESULTS: Membership in the more active PA classes was consistently associated with lower odds of all risk factors for the MS. However, when participants were categorized into quartiles of the coefficients of variation of PA across 7 days, few differences were seen in any of the risk factors. CONCLUSIONS: Accumulating the total weekly recommended amount of PA is consistently associated with positive health profiles, and more PA than the recommended amounts may be even better. However, the manner in which this activity is accumulated, either spread over most days of the week or compressed into just a couple of days, may have similar associations with the risk factors for the MS.

Progressive adaptive physical activity in stroke improves balance, gait, and fitness: preliminary results.

PURPOSE: We conducted a non-controlled pilot intervention study in stroke survivors to examine the efficacy of low-intensity adaptive physical activity to increase balance, improve walking function, and increase cardiovascular fitness and to determine whether improvements were carried over into activity profiles in home and community. METHOD: Adaptive physical activity sessions were conducted 3 times/week for 6 months. The main outcomes were Berg Balance Scale, Dynamic Gait Index, 6-Minute Walk Test, cardiovascular fitness (VO2 peak), Falls Efficacy Scale, and 5-day Step Activity Monitoring. RESULTS: Seven men and women with chronic ischemic stroke completed the 6-month intervention. The mean Berg Balance baseline score increased from 33.9+/-8.5 to 46+/-6.7 at 6 months (mean+/-SD; p=.006). Dynamic Gait Index increased from 13.7+/-3.0 to 19.0+/-3.5 (p=.01). Six-minute walk distance increased from 840+/-110 feet to 935+/-101 feet (p=0.02). VO2 peak increased from 15.3+/-4.1 mL/kg/min to 17.5+/-4.7 mL/kg/min (p=.03). There were no significant changes in falls efficacy or free-living ambulatory activity. CONCLUSION: A structured adaptive physical activity produces improvements in balance, gait, fitness, and ambulatory performance but not in falls efficacy or free-living daily step activity. Randomized studies are needed to determine the cardiovascular health and functional benefits of structured group physical activity programs and to develop behavioral interventions that promote increased free-living physical activity patterns.

Patterns of objectively measured physical activity in the United States.

PURPOSE: We used latent class analysis (LCA) to assess patterns of physical activity among adults, using the 7 d of accelerometer data from the 2003-2004 NHANES. METHODS: For each participant, we determined the daily minutes of moderate-to-vigorous physical activity (MVPA), vigorous physical activity (VPA), and minutes of MVPA that occurred in bouts of 10 min. Participants were then categorized into patterns of activity, using LCA and adjusting for sociodemographic characteristics. RESULTS: For overall MVPA, five classes of physical activity were defined, including two least active classes, which averaged less than 25 min of MVPA per day and represented 78.7% of the total study population. The most active class averaged 134 min of MVPA per day and comprised 0.9% of the population. The results for bout minutes of MVPA were similar to the patterns produced for overall MVPA, with the exception of a "weekend warrior" class with moderate levels of physical activity Monday through Friday but with a much higher level of activity on the weekend, particularly on Sunday. This class represented 1.8% of the population. Only 1.4% of all days achieved 10 min or more of VPA, and in 91.1% of all days, participants accumulated less than 1 min of VPA. The LCA analysis of VPA did not produce stable results, because of the small number of participants registering any minutes of VPA. CONCLUSION: Our results indicate that a very large portion of the U.S. population may be classified into patterns of physical activity that represent low levels of MVPA throughout the week. The LCA analysis provided a novel approach for assessing patterns of objectively measured physical activity in epidemiologic studies.

An integrated multi-institutional diabetes prevention program improves knowledge and healthy food acquisition in northwestern Ontario First Nations.

This article presents the impact results of a feasibility study in Canada for prevention of risk factors for diabetes in seven northwestern Ontario First Nations. Baseline and follow-up data were collected before and after the 9-month intervention program in schools, stores, and communities that aimed to improve diet and increase physical activity among adults. Regression analyses indicate a significant change in knowledge among respondents in intervention communities (p < .019). There was also a significant increase in frequency of healthy food acquisition among respondents in the intervention communities (p < .003). There were no significant changes in physical activity or body mass index in either intervention or comparison groups. The multi-institutional approach demonstrated promising results in modifying selected risk factors for diabetes First Nations communities.

Objectively assessed associations between physical activity and body composition in middle-school girls: the Trial of Activity for Adolescent Girls.

Declining levels of physical activity probably contribute to the increasing prevalence of overweight in US youth. In this study, the authors examined cross-sectional and longitudinal associations between physical activity and body composition in sixth- and eighth-grade girls. In 2003, girls were recruited from six US states as part of the Trial of Activity for Adolescent Girls. Physical activity was measured using 6 days of accelerometry, and percentage of body fat was calculated using an age- and ethnicity-specific prediction equation. Sixth-grade girls with an average of 12.8 minutes of moderate-to-vigorous physical activity (MVPA) per day (15th percentile) were 2.3 times (95% confidence interval: 1.52, 3.44) more likely to be overweight than girls with 34.7 minutes of MVPA per day (85th percentile), and their percent body fat was 2.64 percentage points greater (95% confidence interval: 1.79, 3.50). Longitudinal analyses showed that percent body fat increased 0.28 percentage points less in girls with a 6.2-minute increase in MVPA than in girls with a 4.5-minute decrease (85th and 15th percentiles of change). Associations between MVPA in sixth grade and incidence of overweight in eighth grade were not detected. More population-based research using objective physical activity and body composition measurements is needed to make evidence-based physical activity recommendations for US youth.

Travel by walking before and after school and physical activity among adolescent girls.

OBJECTIVE: To examine how "travel by walking" before and after school contributes to total physical activity of adolescent girls. DESIGN: Cross-sectional sample. SETTING: Thirty-six middle schools from Arizona, Maryland, Minnesota, Louisiana, California, and South Carolina participating in the Trial of Activity for Adolescent Girls (TAAG). PARTICIPANTS: Seventeen hundred twenty-one sixth-grade girls consented to participate; adequate information was available for 1596 participants (93%). MAIN EXPOSURE: Travel by walking before school, after school, and before and after school combined assessed from the 3-Day Physical Activity Recall. MAIN OUTCOME MEASURE: Mean minutes of physical activity measured by accelerometry were estimated for total physical activity (light, moderate, vigorous), moderate to vigorous activity (MVPA), and MVPA of 3 metabolic equivalents. RESULTS: Travel by walking was reported by 14% of participants before school and 18% after school. Girls who reported travel by walking before and after school (combined) had 13.7 more minutes (95% confidence interval, 1.2-26.3) of total physical activity and 4.7 more minutes (95% confidence interval, 2.2-7.2) of MVPA than girls who did not report this activity. Before-school and after-school walkers (but not both) accumulated 2.5 more minutes (95% confidence interval, 0.10-4.9) and 2.2 more minutes (95% confidence interval, 0.24-4.2) of MVPA on an average weekday, respectively, than nonwalkers. CONCLUSION: Our results provide evidence that walking to and from school increases weekday minutes of total physical activity and MVPA for middle-school girls.

Validating accelerometry as a measure of physical activity and energy expenditure in chronic stroke.

BACKGROUND: Accelerometers can objectively measure steps taken per day in individuals without gait deficits, but accelerometers also have the ability to estimate frequency, intensity, and duration of physical activity. However, thresholds to distinguish varying levels of activity intensity using the Actical brand accelerometer are standardized only for the general population and may underestimate intensity in stroke. OBJECTIVE: To derive Actical activity count thresholds specific to stroke disability for use in more accurately gauging time spent at differing activity levels. METHODS: Men (n = 18) and women (n = 10) with chronic hemiparetic gait (4 ± 2 years latency, 43% Caucasian, 56% African-American, ages of 47-83 years, BMI 19-48 kg/m2) participated in the study. Actical accelerometers were placed on the non-paretic hip to obtain accelerometry counts during eight activities of varying intensity: (1) watching TV; (2) seated stretching; (3) standing stretching; (4) floor sweeping; (5) stepping in place; (6) over-ground walking; (7) lower speed treadmill walking (1.0 mph at 4% incline); and (8) higher speed treadmill walking (2.0 mph at 4% incline). Simultaneous portable monitoring (Cosmed K4b2) enabled quantification of energy cost for each activity in metabolic equivalents (METs, or oxygen consumption in multiples of resting level). Measurements were obtained for 10 min of standard rest and 5 min during each of the eight activities. RESULTS: Regression analysis yielded the following new stroke-specific Actical minimum thresholds: 125 counts per minute (cpm) for sedentary/light activity, 667 cpm for light/moderate activity, and 1546 cpm for moderate/vigorous activity. CONCLUSION: Our revised cut points better reflect activity levels after stroke and suggest significantly lower thresholds relative to those observed for the general population of healthy individuals. We conclude that the standard, commonly applied Actical thresholds are inappropriate for this unique population.

Physical activities in adolescent girls: variability in energy expenditure.

BACKGROUND: Understanding interindividual variability of energy expended in common activities is important for determining precise estimates of energy expenditure in surveillance studies and clinical trials. The purpose of this study was to describe the variability in energy expenditure for selected physical activities among adolescent girls. METHODS: Seventy-four adolescent girls (aged 13 to 14 years) participated in this cross-sectional investigation. Data were collected in 2001 and analyzed in 2004. Energy expenditure was measured by indirect calorimetry for ten activities and during a submaximal cycle ergometer test, which was used to estimate cardiorespiratory fitness. Variability in energy expended for the various activities was expressed by standard deviation, coefficient of variation, and range for three different energy expenditure variables: relative VO2 (milliliters per kilogram per minute), absolute VO2 (liters per minute(-1)), and calculated metabolic rate (kilojoules per minute). RESULTS: Depending on the expression of energy expenditure, coefficients of variation ranged from a low of 13.2% for climbing stairs to a high of 38.4% for playing a computer game. Some lower-intensity activities were associated with greater variability in energy expenditure. Bicycling showed consistently higher coefficients of variation across expressions of energy expenditure (29.1%, 37.7%, and 33.5% for relative VO2, absolute VO2, and calculated metabolic rate, respectively). CONCLUSIONS: Energy expenditure for common activities is highly variable in adolescent girls. The coefficient of variation was higher in some activities of lower intensity, regardless of energy expenditure expression. This variance may influence the evaluation of physical activity interventions, particularly with regard to issues such as a prescribed dose of activity and the statistical power to detect change.

Associations of body size and composition with physical activity in adolescent girls.

PURPOSE: To examine whether components of body composition (size, fat mass, and fat-free mass) were related to physical activity. METHODS: A random sample of 60 eligible sixth grade girls at each of 36 schools (six schools per region and six regions in total sample); complete measurements on 1,553 girls. Physical activity was assessed over 6 d in each girl using an accelerometer, and body composition was assessed using a multiple regression equation using body mass index and triceps skinfold. Minutes of moderate-to-vigorous and vigorous physical activity were estimated from accelerometer counts per 30 s above threshold values determined from a previous study. RESULTS: Significant inverse relationships were found for all measures of body size and composition and all physical activity indices. The combination of fat and fat-free mass expressed as a weight and as an index (divided by height squared) along with race, SES, site, and school were most highly associated with physical activity in multiple regression analysis, accounting for 14-15% of the variance in physical activity. Fat mass was more closely related to moderate-to-vigorous physical activity (MVPA) and vigorous physical activity (VPA) than fat-free mass with higher standardized regression coefficients. CONCLUSION: We conclude that both fat mass or fat mass index as well as fat-free mass or fat-free mass index make independent contributions in association with physical activity levels. These indices are recommended for future studies.

Increased Energy Cost of Mobility in Chronic Stroke.

The purpose of this study was to compare the energy cost of completing mobility-related activities in chronic stroke to the estimated energy cost found in the compendium of physical activities, a resource that estimates and classifies energy cost of various human physical activities. Men (n=18) and women (n=10) with chronic hemiparetic gait (stroke latency: 4 ± 2 years, age: 60.4 ± 1.6 years, BMI: 31.5 ± 1.1 kg/m2) participated in the study. Portable energy cost monitoring (COSMED K4b2) was performed during five mobility activities of varying intensity to determine metabolic equivalents (METs, or oxygen consumption in multiples of resting level) for each activity. The METs achieved during the five activities were compared to the following compendium MET values for: 1) floor sweeping; 2) stepping in place; 3) over-ground walking; 4) lower speed treadmill walking (1.0 mph at 4% incline); and 5) higher speed treadmill walking (2.0 mph at 4% incline). Measurements were obtained for 10 min at rest and 5 minutes during each of the five activities. The energy cost of rest was only 85% of Compendium METS, while mobility-related activities were ~1.25-1.50 fold greater when measured in stroke vs. Compendium METS for all measures (P's<0.05), except floor sweeping, which was similar between groups. These data indicate that MET levels provided in the compendium are not applicable to chronic stroke survivors as they overestimate energy expenditure at rest and underestimate energy expenditure during physical activity, indicating poor efficiency in movement, thus elevating the oxygen cost of completing general daily activities.

Pregnancy-related changes in physical activity, fitness, and strength.

PURPOSE: The objective was to examine the pregnancy-related changes in physical activity, fitness, and strength in women of varying body mass indices (BMI). METHODS: Women (N = 17 low BMI, N = 34 normal BMI, and N = 12 high BMI, mean age +/- SD = 30.7 +/- 4.1 yr) were studied before pregnancy (0 wk) and postpartum (6 and 27 wk) for body composition and for physical activity, fitness, and strength. Physical activity was assessed by questionnaire, fitness by a maximal oxygen consumption (VO2) test on a cycle ergometer, and strength by the one-repetition maximum test. Data were analyzed by repeated measures ANOVA testing for time and BMI group. RESULTS: Total physical activity differed qualitatively, but not quantitatively, with time. Significant time effects were observed for maximal workload, heart rate, respiration rate, ventilation, VO2, respiratory exchange ratio, and strength. VO2max, adjusted for weight, dropped by approximately 385 mL x min(-1) from 0 to 6 wk postpartum (P < 0.0001) and by approximately 234 mL x min(-1) from 0 to 27 wk postpartum (P < 0.01). The high-BMI group had a lower VO2max (adjusted for weight or fat-free mass) than the normal-BMI group (P < 0.05). Strength decreased for the leg press by 24% (P < 0.02) and for the latissimus pull down by 8% (P < 0.01) from 0 to 6 wk postpartum, and then increased by 44 and 12%, respectively (both P < 0.05), by 27 wk postpartum. CONCLUSION: Relative to prepregnancy performance, fitness and strength declined in the early postpartum period but improved by 27 wk postpartum.

Validity and reliability of the Fels physical activity questionnaire for children.

PURPOSE: The aim was to evaluate the reliability and validity of the Fels physical activity questionnaire (PAQ) for children 7-19 yr of age. METHODS: A cross-sectional study was conducted among 130 girls and 99 boys in elementary (N=70), middle (N=81), and high (N=78) schools in rural Maryland. Weight and height were measured on the initial school visit. All the children then wore an Actiwatch accelerometer for 6 d. The Fels PAQ for children was given on two separate occasions to evaluate reliability and was compared with accelerometry data to evaluate validity. RESULTS: The reliability of the Fels PAQ for the girls, boys, and the elementary, middle, and high school age groups range was r=0.48-0.76. For the elementary school children, the correlation coefficient examining validity between the Fels PAQ total score and Actiwatch (counts per minute) was 0.34 (P=0.004). The correlation coefficients were lower in middle school (r=0.11, P=0.31) and high school (r=0.21, P=0.006) adolescents. The sport index of the Fels PAQ for children had the highest validity in the high school participants (r=0.34, P=0.002). CONCLUSION: The Fels PAQ for children is moderately reliable for all age groups of children. Validity of the Fels PAQ for children is acceptable for elementary and high school students when the total activity score or the sport index is used. The sport index was similar to the total score for elementary students but was a better measure of physical activity among high school students.

Ankle Accelerometry for Assessing Physical Activity Among Adolescent Girls: Threshold Determination, Validity, Reliability, and Feasibility.

PURPOSE: Ankle accelerometry allows for 24-hr data collection and improves data volume/integrity versus hip accelerometry. Using Actical ankle accelerometry, the purpose of this study was to (a) develop sensitive/specific thresholds, (b) examine validity/reliability, (c) compare new thresholds with those of the manufacturer, and (d) examine feasibility in a community sample (low-income, urban adolescent girls). METHOD: Two studies were conducted with 6th- through 7th-grade girls (aged 10-14 years old): First was a laboratory study (n = 24), in which 2 Actical accelerometers were placed on the ankle and worn while measuring energy expenditure (Cosmed K4b2, metabolic equivalents [METs]) during 10 prescribed activities. Analyses included device equivalence reliability (intraclass correlation coefficient [ICC], activity counts of 2 Acticals), criterion-related validity (correlation, activity counts and METs), and calculations of sensitivity, specificity, kappa, and receiver-operating characteristic curves for thresholds. The second was a free-living study (n = 459), in which an Actical was worn for more than 7 days on the ankle (full 24-hr days retained). Analyses included feasibility (frequencies, missing data) and paired t tests (new thresholds vs. those of the manufacturer). RESULTS: In the laboratory study, the Actical demonstrated reliability (ICC = .92) and validity (r = .81). Thresholds demonstrated sensitivity (91%), specificity (84%), kappa = .73 (p = .043), area under curve range = .81-.97. In the free-living study, 99.6% of participants wore the accelerometer; 84.1% had complete/valid data (mean = 5.7 days). Primary reasons for missing/invalid data included: improper programming/documentation (5.2%), failure to return device (5.0%), and wear-time ≤ 2 days (2.8%). The moderate-to-vigorous physical activity threshold (> 3,200 counts/minute) yielded 37.2 min/day, 2 to 4.5 times lower than that of the manufacturer's software (effect size = 0.74-4.05). CONCLUSIONS: Validity, reliability, and feasibility evidences support Actical ankle accelerometry to assess physical activity in community studies of adolescent girls. When comparing manufacturers' software versus new thresholds, a major difference was observed.

Effects of dietary macronutrient content on glucose metabolism in children.

Effects of carbohydrate, fat, and fructose intake on substrate and hormone concentrations, glucose production, gluconeogenesis, and insulin sensitivity were determined in healthy, nonobese prepubertal children (n = 12) and adolescents (n = 24) using a cross-over design. In one group (12 prepubertal children and 12 adolescents), subjects were studied after 7 d of isocaloric, isonitrogenous diets providing either 60% carbohydrate and 25% fat [high carbohydrate (H(CHO))/low fat (L(F))] or 30% carbohydrate and 55% fat [low carbohydrate (L(CHO))/high fat (H(F))], and in a second group (12 adolescents) H(CHO)/L(F) diets containing either 40% or 10% fructose was used. All subjects adapted to changes in carbohydrate and fat intakes primarily by appropriately adjusting their substrate oxidation rates to match the intakes, with only minor changes in parameters of glucose metabolism. Changing from a L(CHO)/H(F) to H(CHO)/L(F) diet resulted in increased insulin sensitivity (stable labeled iv glucose tolerance test) in adolescents [from 3.2 +/- 0.7 x 10(-4) to 5.0 +/- 1.4 x 10(-4) (min(-1))/( micro U.ml(-1)) (mean +/- SE)] but not in prepubertal children [9.4 +/- 2.5 x 10(-4) to 9.9 +/- 1.5 x 10(-4) (min(-1))/( micro U.ml(-1))], whereas beta-cell sensitivity was unaffected in both groups. Insulin sensitivity was higher in prepubertal children than in adolescents (P < 0.05). The dietary fructose content did not affect any measured parameter. We conclude that in the short term, dramatic changes in fat and carbohydrate intakes (regardless of fructose content) did not adversely affect glucose and lipid metabolism in healthy nonobese children. In the adolescents, the high carbohydrate diet resulted in increased insulin sensitivity, thus facilitating insulin-mediated glucose uptake.

Predictors of body fat gain in nonobese girls with a familial predisposition to obesity.

BACKGROUND: Conflicting evidence exists on the causal factors underlying the development of excess adiposity in children. OBJECTIVE: We determined the effect of energy expenditure (EE), muscle energetics, and physical fitness on weight and fat gain in prepubertal girls with or without a predisposition to obesity. DESIGN: Normal-weight girls (n = 101) were recruited at 8 y of age according to parental body mass index. Eighty-eight girls completed the 2-y study, and the groups were as follows: LN, girls with 2 lean parents; LNOB, girls with 1 obese and 1 lean parent; and OB, girls with 2 obese parents. Measurements of weight, height, and body composition were taken 1 and 2 y after baseline. Girls underwent baseline measurements of EE by 24-h calorimetry and doubly labeled water, of muscle metabolism by (31)P nuclear magnetic resonance, and of fitness. RESULTS: Fat mass (FM) and percentage body fat (%BF) differed significantly between the groups at years 1 and 2; the OB group had higher FM (P = 0.03) and %BF (P = 0.046) at year 1 and higher FM (P = 0.047) at year 2 than did the LN group. After adjustment for baseline weight, group, time, ethnicity, and Tanner stage, sleep EE, basal EE, 24-h EE, and peak oxygen uptake were negatively associated with FM and %BF (P < 0.04). After adjustment for the same variables, muscle oxidative capacity and free-living total EE were negatively and positively predictive, respectively, of changes in %BF between 8 and 10 y of age (both P = 0.04). CONCLUSIONS: Nonobese girls with 2 obese parents have a significant risk of developing obesity. High free-living total EE and low muscle oxidative capacity predict high rates of fat gain.

Energy requirements during pregnancy based on total energy expenditure and energy deposition.

BACKGROUND: Energy requirements during pregnancy remain controversial because of uncertainties regarding maternal fat deposition and reductions in physical activity. OBJECTIVE: This study was designed to estimate the energy requirements of healthy underweight, normal-weight, and overweight pregnant women and to explore energetic adaptations to pregnancy. DESIGN: The energy requirements of 63 women [17 with a low body mass index (BMI; in kg/m(2)), 34 with a normal BMI, and 12 with a high BMI] were estimated at 0, 9, 22, and 36 wk of pregnancy and at 27 wk postpartum. Basal metabolic rate (BMR) was measured by calorimetry, total energy expenditure (TEE) by doubly labeled water, and activity energy expenditure (AEE) as TEE - BMR. Energy deposition was calculated from changes in body protein and fat. Energy requirements equaled the sum of TEE and energy deposition. RESULTS: BMR increased gradually throughout pregnancy at a mean (+/-SD) rate of 10.7 +/- 5.4 kcal/gestational week, whereas TEE increased by 5.2 +/- 12.8 kcal/gestational week, which indicated a slight decrease in AEE. Energy costs of pregnancy depended on BMI group. Although total protein deposition did not differ significantly by BMI group (mean for the 3 groups: 611 g protein), FM deposition did (5.3, 4.6, and 8.4 kg FM in the low-, normal-, and high-BMI groups; P = 0.02). Thus, energy costs differed significantly by BMI group (P = 0.02). In the normal-BMI group, energy requirements increased negligibly in the first trimester, by 350 kcal/d in the second trimester, and by 500 kcal/d in the third trimester. CONCLUSION: Extra energy intake is required by healthy pregnant women to support adequate gestational weight gain and increases in BMR, which are not totally offset by reductions in AEE.