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BACKGROUND: Obesity is a serious issue, spanning all ages, and, in the U.S., disproportionately affects Latinos and African Americans. Understanding sleep, physical activity and dietary behaviors that may predict childhood obesity can help identify behavioral intervention targets. METHODS: Data were drawn from a U.S. cohort study of 323 Mexican American 8-10-year-old children and their mothers, who participated in a longitudinal study over a 2-year period. Measures were collected at baseline (BL; child mean age = 8.87, SD = 0.83), year 1 (FU1) and year 2 (FU2). Mothers reported on household income and acculturation at BL. Child height and weight were collected and BMI z-scores (BMIz) were calculated for weight status at BL, FU1, and FU2. Accelerometer-estimated sleep duration (hours) and moderate-to-vigorous physical activity (MVPA; minutes) were collected across 3 days at BL, FU1, and FU2. Two 24-h dietary recalls were performed at each time point; from these, average energy intake (EI, kcals/day) was estimated. Cross-lagged panel analysis was used to examine behavioral predictors on BMIz at each time point and across time. RESULTS: At BL and FU1, longer sleep duration (ß = - 0.22, p < 0.001; ß = - 0.17, p < 0.05, respectively) and greater MVPA (ß = - 0.13, p < 0.05; ß = - 0.20, p < 0.01, respectively) were concurrently related to lower BMIz. At FU2, longer sleep duration (ß = - 0.18, p < 0.01) was concurrently related to lower BMIz, whereas greater EI (ß = 0.16, p < 0.01) was related to higher BMIz. Longer sleep duration at BL predicted lower BMIz at FU1 (ß = - 0.05, p < 0.01). CONCLUSIONS: Longer sleep duration was concurrently related to lower weight status at each time point from ages 8-10 to 10-12. Higher MVPA was concurrently related to lower weight status in earlier childhood (ages 8-10 and 9-11) and higher EI was concurrently related to higher weight status toward the end of childhood (ages 10-12 years). Furthermore, longer sleep in earlier childhood was protective of children's lower weight status 1 year later. These findings suggest that sleep duration plays a consistent and protective role against childhood obesity; in addition, MVPA and healthy EI remain important independent factors for obtaining a healthy weight.

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OBJECTIVE: This study aimed to examine the relationship between circadian sleep and activity behaviors (sedentary time [SED], light-intensity physical activity [LPA], and moderate- to vigorous-intensity physical activity [MVPA]) across 3 consecutive days. METHODS: This study included 308 Mexican American children aged 8-10 years from the San Francisco Bay Area. Minutes of sleep duration, SED, LPA, and MVPA were estimated using hip-worn accelerometers from Wednesday night to Saturday night. A cross-lagged panel model was used to estimate paths between sleep duration the prior night and subsequent behaviors, and paths between behaviors to subsequent sleep duration across the 3 days. We adjusted for child age, sex, body mass index, and household income. RESULTS: Overall, children were 8.9 (SD 0.8) years old; the weighted average for weekday and weekend combined was 9.6 (SD 0.7) hours per night in sleep duration, 483 (SD 74) min/d SED, 288 (SD 61) min/d LPA, and 63 (SD 38) min/d MVPA. Cross-lagged panel analyses showed that, over 3 days, for every 1-hour increase in sleep duration, there were an expected 0.66-hour (40-minute) decrease in SED, 0.37-hour (22-minute) decrease in LPA, and 0.06-hour (4-minute) decrease in MVPA. For every 1-hour increase in LPA, there was an expected 0.25-hour (15-minute) decrease in sleep duration. CONCLUSION: An additional hour of sleep the night before corresponded to an hour decrease in combined SED and LPA the next day in Mexican American children. For every hour of LPA, there was an associated 15-minute decrease in sleep. Encouraging longer sleep may help to reduce SED and LPA, and help offset LPA's negative predictive effect on sleep.

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OBJECTIVE: To determine the effect of stimulant medications used to treat children with attention-deficit/hyperactivity disorder (AD/HD) on energy expenditure, fuel utilization, and physical activity. STUDY DESIGN: Energy expenditure and physical activity were measured, respectively, by room respiration calorimetry and microwave motion detectors in 31 children with AD/HD (26 boys and 5 girls; ages 6 to 12 years) both while they were receiving their prescribed stimulant medication and after the medication had been discontinued for at least 24 hours. Fuel utilization was calculated from calorimetry data. RESULTS: Total and awake energy expenditure including energy expended while doing schoolwork, riding a stationary bicycle, resting, and watching a movie were from 4% to 8% lower when the children were receiving their prescribed stimulant medication. Total and awake activity were also lower while they were receiving medication (16% to 22%) and accounted for the lower rates of energy expenditure. Sleeping metabolic rate, basal metabolic rate, and fuel utilization were unaffected by medication. CONCLUSIONS: Stimulant medications decrease physical activity, and hence, decrease the activity component of total daily energy expenditure in children with AD/HD.

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The milk composition of women on a typical rural Mexican diet was compared with that secreted by American women, consuming a diet typical of affluent countries. Milk concentrations of free fatty acids, cholesterol, total amino acids, and selected key minerals were analyzed at 4 or 6 months postpartum. The total milk fat concentration was lower in the Otomi (22.7 +/- 6.7 mg/g milk) than in the American women (31.3 +/- 5.4 mg/g milk, p = 0.001). Although the absolute concentration did not differ, cholesterol, expressed in terms of total lipid, was higher in the Otomi milk (3.9 +/- 1.1 vs. 3.1 +/- 0.7 mg/g fat, p = 0.005). Saturated medium-chain (C10:0-C14:0) and unsaturated intermediate-chain fatty acids (C16:1 and C18:2) were higher in the Otomi than in the American milk (p < 0.03). The concentrations of C16:0, C18:0, and C18:1 were significantly lower in Otomi than in American milk. The milk concentrations of protein and nonprotein nitrogen were comparable between the two groups. The concentrations of serine, proline, cystine, methionine, and tryptophan were higher in the Otomi than in the American milk (p < 0.05-0.001). The concentrations of valine and isoleucine were significantly lower in the Otomi milk (p = 0.05). Expressed per gram of milk protein, the cystine, methionine, lysine, and tryptophan concentrations were higher, and the glutamine/glutamate, valine, isoleucine, and arginine levels were lower in the Otomi milk. The concentrations of phosphorus and copper were lower in the Otomi than in the American milk at 4 months postpartum (p = 0.05). These differences in milk fatty acid and amino acid patterns and mineral content are unlikely to affect infant growth, but may have other biological consequences yet to be ascertained.

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Energy-sparing mechanisms may be elicited to meet increased energy requirements imposed by lactation on women who reside in poor, rural communities in developing countries. The objectives of this study were to measure total energy expenditure and its components, basal and activity energy expenditure, and to investigate their relationships with lactation performance in a total of 40 rural Mesoamerindians stratified according to postpartum body mass index. Total energy expenditure and fat-free mass were measured by the doubly labeled water method, and basal metabolic rate was determined by indirect calorimetry at 3 and 6 mo postpartum. Physical activity level was taken as the ratio of total energy expenditure to basal metabolic rate. Milk energy output, which is not included in total energy expenditure, was computed from 24-h milk intake (test-weighing) and energy concentration of milk (bomb calorimetry). Anthropometric measurements revealed negligible mobilization of tissue stores. Mean (+/- SD) total energy expenditures were 8912 +/- 1296 kJ/d and 9253 +/- 1298 kJ/d for the lower and higher body mass index groups, respectively. Adjusted for fat-free mass, total energy expenditure was higher in the lower body mass index group (P = 0.05). Adjusted for fat-free mass, basal metabolic rate did not differ between groups. Physical activity level was significantly higher in the lower body mass index group (P = 0.03). Lactation performance did not differ between groups and was not associated with total energy expenditure or its components. Despite the maintenance of energy balance and heightened energy requirements of lactation, energy-sparing mechanisms were not evident in these lactating Mesoamerindians.

PIP: The authors measured total energy expenditure and its components, basal and activity energy expenditure, and investigated their relationships with lactation performance among 40 rural Mesoamerindians stratified according to postpartum body mass index. Total energy expenditure and fat-free mass were measured by the doubly-labeled water method, and basal metabolic rate was determined by indirect calorimetry at 3 and 6 months postpartum. The ratio of total energy expenditure to basal metabolic rate identified the physical activity level, while milk energy output was computed from 24-hour milk intake test and the energy concentration of milk. Anthropometric measurements identified negligible mobilization of tissue stores. Mean total energy expenditures were 8912 kJ/day and 9253 kJ/day for the lower and higher body mass index groups, respectively. Adjusted for fat-free mass, total energy expenditure was higher in the lower body mass index group, although the basal metabolic rate did not differ between groups. The physical activity level was significantly higher in the lower body mass index group. Lactation performance did not differ between groups and was not associated with total energy expenditure or its components. Despite the maintenance of energy balance and heightened energy requirements of lactation, energy-sparing mechanisms were not evident in these lactating Mesoamerindians.

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To investigate the energy requirements of infants living under unfavorable environmental conditions in rural Mexico, we measured the total energy expenditure (TEE) of 40 Otomi infants at approximately 4 or approximately 6 mo of age. Total energy expenditure was estimated by the doubly labeled water method: 100 mg 2H2O/kg and 250 mg 18O/kg were administered orally, after which urine was collected serially for 7 or 10 d. Isotopic enrichment of urine samples was analyzed by gas-isotope-ratio mass spectrometry. Weight and length were measured monthly from birth to 6 mo. Fat free mass was estimated from 18O dilution spaces. Total energy expenditures (mean +/- SD) were 310 +/- 58 and 318 +/- 29 kJ.kg-1 x d-1 at approximately 4 and approximately 6 mo, respectively. Total energy expenditure was higher than that previously observed for breast-fed infants reared under more protected environments (268 +/- 29 kJ.kg-1 x d-1). Weight, length and weight gain were 5.9 +/- 0.8 kg, 60 +/- 2 cm and 2.9 +/- 2.4 g.kg-1 x d-1 at 4.25 mo and 7.1 +/- 0.8 kg, 65 +/- 2 cm and 1.0 +/- 1.2 g.kg-1 x d-1 at 6.27 mo. Growth faltering was evident at 6 mo by clinically significant declines in growth velocities and National Center for Health Statistics Z-scores. Body fat of the Otomi infants averaged 21 +/- 6 and 18 +/- 5 g/100 g at approximately 4 and approximately 6 mo, respectively. Higher rates of TEE narrowed the margin of energy available for growth and thereby contributed to growth faltering in the Otomi infants.

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To determine whether growth faltering during early infancy was attributable to inadequate intake of human milk, the nutrient intakes and growth of 30 Otomi infants from Capulhuac, Mexico, were studied at 4 or 6 mo of age. Growth was monitored monthly from 1 through 6 mo of age. The 2H dose-to-the-mother method was used to measure human milk intake. Energy, protein, lactose, and fat concentrations in milk were analyzed by standard techniques. Mean (+/- SD) human milk intakes were 885 +/- 145 and 869 +/- 150 g/d at 4 and 6 mo, respectively. Protein and lactose concentrations in milk were normal but fat and consequently energy concentrations were abnormally low. Energy intakes averaged 81 +/- 14 kcal.kg-1.d-1 at 4 mo and 72 +/- 14 kcal.kg-1.d-1 at 6 mo. Growth faltering by 6 mo was evidenced by the significant decline in growth velocities and National Center for Health Statistics Z scores. Weight gain at 6 mo was 8.1 +/- 3.5 g/d and length gain was 1.0 +/- 0.34 cm/mo. Weight-for-age and length-for-age Z scores were -0.81 +/- 0.94 and -1.51 +/- 0.83, respectively. Growth velocities were not significantly correlated with nutrient intakes. Growth faltering among the Otomi infants despite energy intakes comparable to those of breast-fed infants in more protected environments may have resulted from an increase in the need for nutrients or from a growth-limiting nutrient, other than energy, in their diet.

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Anthropometry, body composition and dietary intake of 30 lactating Otomi Indians of Capulhuac, Mexico, were studied to identify maternal factors which potentially limit lactation and thereby infant growth. Human milk production, milk composition, and maternal dietary intake, body weight, skinfold thicknesses, and body composition were measured at 4 and 6 months postpartum. The 2H2O dose-to-mother method was used to estimate milk production and maternal total body water (TBW). Fat-free mass (FFM) was calculated as TBW/0.73. Body fat was computed as body weight minus FFM. Human milk samples were analyzed for energy, nitrogen, lactose and fat using standard analytical methods. Maternal diet was assessed by three 24-h intake recalls. Mean (SD) milk production was 885 (146) and 869 (150) g/d at 4 and 6 months, respectively. Milk concentrations of protein nitrogen (1.23 (0.17) mg/g) and lactose (66.6 (2.8) mg/g) were comparable to, but the concentrations of fat (22.2 (6.7) mg/g) and energy (0.54 (0.06) kcal/g) were lower than, values observed in economically privileged populations. Maternal height, weight, and BMI were 1.47 (0.06) m, 50.3 (6.0) kg, and 23.4 (3.1) kg/m2, respectively. Maternal TBW, FFM and body fat were 55.8 (4.6)%, 76.4 (6.3)%, and 23.6 (6.4)%, expressed as a percentage of body weight, respectively. Maternal energy and protein intakes averaged 1708 (338) kcal/d and 40 (10) g/d, respectively. Milk production was negatively correlated with maternal body fat (P = 0.006). Energy and fat concentrations in the milk of the Otomi women were positively related to their weight (P = 0.002), BMI (P = 0.05), and body fat (P = 0.004). Energy concentrations in milk were not related to rates of milk production (r = 0.24; P = 0.23). Nor was milk production or composition significantly associated with maternal dietary intake. Lactation performance of these Otomi women correlated significantly with maternal body size and composition, but not current dietary intake.

PIP: Researchers analyzed data on 30 postpartum women from the Otomi Indian community living in rural Capulhuac, Mexico to examine interrelationships among lactation performance, maternal body size/composition, and dietary intake to learn which maternal factors limit lactation and thus infant growth. Infant food supplementation was minimal. Current diet did not affect milk production or levels of energy and fat in milk. Even though the body mass index (BMI) was lower than the normal range (19.8-26 kg/sq meter) for only 2 women, 8 women had 20% body fat indicating considerable undernutrition. Women consumed a mean of 68% and 80% of energy and protein requirements. Mean energy intakes (kcal/kg/day) at 4 and 6 months postpartum were 33.8 and 35.1 respectively, compared with the recommended 51. Mean protein intakes (g/kg/day) were 0.75 and 0.84 respectively compared with the recommended 1.1 3-day intake records based on memory, estimation of portion sizes, food preparation, and food composition data led to the above energy intake results, but they may not have been accurate since a mean of 35 would not allow much physical activity. Fats and carbohydrates mainly from maize made up 17% and 76% respectively of the Otomi diet suggesting a suboptimal diet. Yet human milk production rates (885 g/day at 4 months and 869 g/day at 6 months) tended to equal or be higher than those of women of higher socioeconomic status (711-925 g/day) and other poor women (525-789 g/day). The greater the levels of maternal body fat the smaller the amount of milk women produced (p=.006). Total nitrogen, protein nitrogen, lactose, and nonprotein nitrogen levels fell within the range of that of privileged women. Fat and energy levels in the milk were lower than those of privileged women, however heavy women (p=.002) with high BMI (p=.05) and body fat (p=.004) levels tended to have high levels of energy and fat in the milk. Energy levels in milk were not linked with milk production. Neither milk production nor composition were related to dietary intake.

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A discrepancy between current recommendations for energy intakes and the reported intakes of human milk-fed infants has led to the suggestion that energy requirements of infants should be reevaluated. Gross energy intakes of 1-month-old, exclusively breast-fed infants are similar to recommended amounts of metabolizable energy; however, by 4 months of age, gross energy intakes of exclusively breast-fed infants are significantly less than current recommendations. Weight-for-age percentiles also fall during that period. Energy intakes (measured in kilocalories per kilogram) persist at less than recommended amounts, and weight-for-age percentiles continue to drop after solid foods are added to the diet. Energy intakes of formula-fed infants appear significantly higher than those of infants who are fed human milk. Growth rates, total daily energy expenditure, sleeping metabolic rates, minimal rates of energy expenditure, rectal temperature, and heart rates have been found to be lower in breast-fed infants. The maintenance of energy intakes and growth trajectories during the period of demand supplementation with solid foods suggests that intakes, growth rates, and rates of energy expenditure of human milk-fed infants are physiologic responses to an appropriate dietary intake.

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Milk intake and growth in 45 exclusively breast-fed infants were documented during the first 4 months of life. Energy and protein intakes were substantially less than current nutrient allowances. Energy intake declined significantly from 110 +/- 24 kcal/kg/day at 1 month to 71 +/- 17 kcal/kg/day at 4 months. Protein intake decreased from 1.6 +/- 0.3 gm/kg/day at 1 month to 0.9 +/- 0.2 gm/kg/day at 4 months. Infant growth progressed satisfactorily, compared with National Center for Health Statistics standards. A reevaluation of energy and protein intakes and allowances during infancy is merited.

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