Greater male variability in daily energy expenditure develops through puberty.

There is considerably greater variation in metabolic rates between men than between women, in terms of basal, activity and total (daily) energy expenditure (EE). One possible explanation is that EE is associated with male sexual characteristics (which are known to vary more than other traits) such as musculature and athletic capacity. Such traits might be predicted to be most prominent during periods of adolescence and young adulthood, when sexual behaviour develops and peaks. We tested this hypothesis on a large dataset by comparing the amount of male variation and female variation in total EE, activity EE and basal EE, at different life stages, along with several morphological traits: height, fat free mass and fat mass. Total EE, and to some degree also activity EE, exhibit considerable greater male variation (GMV) in young adults, and then a decreasing GMV in progressively older individuals. Arguably, basal EE, and also morphometrics, do not exhibit this pattern. These findings suggest that single male sexual characteristics may not exhibit peak GMV in young adulthood, however total and perhaps also activity EE, associated with many morphological and physiological traits combined, do exhibit GMV most prominently during the reproductive life stages.

Cut-point values for classifying active children and validity and reliability of physical activity questionnaire for children in Morocco.

BACKGROUND: The Physical Activity Questionnaire for Children (PAQ-C) is widely used to assess physical activity in populations; however, there is a lack of information about the psychometric properties (validity and reliability) and about the PAQ-C score meaning in populations from low-middle income countries. AIMS: The aim of this study is to evaluate the reliability and validity of PAQ-C and to determine the cut-point values of PAQ-C using accelerometry as a reference in a group of Moroccan children. METHODS: In a sample of 171 children and adolescents aged 8 to 14 years, physical activity was assessed with the GT3X + accelerometer and the PAQ-C. PAQ-C was administered for a second time (retest) after 1 week for a subsample (n = 73). Reliability was analyzed by intraclass correlation coefficient (ICC). The PAQ-C was compared against count per minute CPM and moderate to vigorous intensity PA (MVPA) obtained by accelerometry. Receiver operating curve analyses were performed to assess the performance of PAQ-C in identifying MVPA as measured by accelerometry (reference method). RESULTS: Test-retest reliability was poor with an ICC = (0.48 [0.27; 0.63] for the whole sample, while for the ≥11 year group, the intra-class correlation coefficient was moderate (0.71 [0.42; 0.86]. PAQ-C scores were significantly related to accelerometry-derived metrics of physical activity, CPM (R = 0.29, P < 0.001) and MVPA (R = 0.26, P < 0.001). For the age group ≥11 years, the associations between PAQ-C Scores and CPM and MVPA were stronger, respectively, R = 0.37 (P < 0.001), R = 0.38 (P < 0.0001). We identified that a PAQ-C Score cut-point of 2.33 (95%CI [0.43-0.68]) discriminated adequately between those who met physical activity guidelines and those that did not in the overall sample. CONCLUSIONS: The PAQ-C is valid and useful to assess population level physical activity in those ≥11 years in Morocco and so might be helpful in population surveillance of physical activity in Moroccan adolescents.

Variation in human water turnover associated with environmental and lifestyle factors.

Water is essential for survival, but one in three individuals worldwide (2.2 billion people) lacks access to safe drinking water. Water intake requirements largely reflect water turnover (WT), the water used by the body each day. We investigated the determinants of human WT in 5604 people from the ages of 8 days to 96 years from 23 countries using isotope-tracking (2H) methods. Age, body size, and composition were significantly associated with WT, as were physical activity, athletic status, pregnancy, socioeconomic status, and environmental characteristics (latitude, altitude, air temperature, and humidity). People who lived in countries with a low human development index (HDI) had higher WT than people in high-HDI countries. On the basis of this extensive dataset, we provide equations to predict human WT in relation to anthropometric, economic, and environmental factors.

Variability in energy expenditure is much greater in males than females.

In mammals, trait variation is often reported to be greater among males than females. However, to date, mainly only morphological traits have been studied. Energy expenditure represents the metabolic costs of multiple physical, physiological, and behavioral traits. Energy expenditure could exhibit particularly high greater male variation through a cumulative effect if those traits mostly exhibit greater male variation, or a lack of greater male variation if many of them do not. Sex differences in energy expenditure variation have been little explored. We analyzed a large database on energy expenditure in adult humans (1494 males and 3108 females) to investigate whether humans have evolved sex differences in the degree of interindividual variation in energy expenditure. We found that, even when statistically comparing males and females of the same age, height, and body composition, there is much more variation in total, activity, and basal energy expenditure among males. However, with aging, variation in total energy expenditure decreases, and because this happens more rapidly in males, the magnitude of greater male variation, though still large, is attenuated in older age groups. Considerably greater male variation in both total and activity energy expenditure could be explained by greater male variation in levels of daily activity. The considerably greater male variation in basal energy expenditure is remarkable and may be explained, at least in part, by greater male variation in the size of energy-demanding organs. If energy expenditure is a trait that is of indirect interest to females when choosing a sexual partner, this would suggest that energy expenditure is under sexual selection. However, we present a novel energetics model demonstrating that it is also possible that females have been under stabilizing selection pressure for an intermediate basal energy expenditure to maximize energy available for reproduction.

Energy compensation and adiposity in humans.

Understanding the impacts of activity on energy balance is crucial. Increasing levels of activity may bring diminishing returns in energy expenditure because of compensatory responses in non-activity energy expenditures.1-3 This suggestion has profound implications for both the evolution of metabolism and human health. It implies that a long-term increase in activity does not directly translate into an increase in total energy expenditure (TEE) because other components of TEE may decrease in response-energy compensation. We used the largest dataset compiled on adult TEE and basal energy expenditure (BEE) (n = 1,754) of people living normal lives to find that energy compensation by a typical human averages 28% due to reduced BEE; this suggests that only 72% of the extra calories we burn from additional activity translates into extra calories burned that day. Moreover, the degree of energy compensation varied considerably between people of different body compositions. This association between compensation and adiposity could be due to among-individual differences in compensation: people who compensate more may be more likely to accumulate body fat. Alternatively, the process might occur within individuals: as we get fatter, our body might compensate more strongly for the calories burned during activity, making losing fat progressively more difficult. Determining the causality of the relationship between energy compensation and adiposity will be key to improving public health strategies regarding obesity.

Global effect of COVID-19 pandemic on physical activity, sedentary behaviour and sleep among 3- to 5-year-old children: a longitudinal study of 14 countries.

BACKGROUND: The restrictions associated with the 2020 COVID-19 pandemic has resulted in changes to young children's daily routines and habits. The impact on their participation in movement behaviours (physical activity, sedentary screen time and sleep) is unknown. This international longitudinal study compared young children's movement behaviours before and during the COVID-19 pandemic. METHODS: Parents of children aged 3-5 years, from 14 countries (8 low- and middle-income countries, LMICs) completed surveys to assess changes in movement behaviours and how these changes were associated with the COVID-19 pandemic. Surveys were completed in the 12 months up to March 2020 and again between May and June 2020 (at the height of restrictions). Physical activity (PA), sedentary screen time (SST) and sleep were assessed via parent survey. At Time 2, COVID-19 factors including level of restriction, environmental conditions, and parental stress were measured. Compliance with the World Health Organizations (WHO) Global guidelines for PA (180 min/day [≥60 min moderate- vigorous PA]), SST (≤1 h/day) and sleep (10-13 h/day) for children under 5 years of age, was determined. RESULTS: Nine hundred- forty-eight parents completed the survey at both time points. Children from LMICs were more likely to meet the PA (Adjusted Odds Ratio [AdjOR] = 2.0, 95%Confidence Interval [CI] 1.0,3.8) and SST (AdjOR = 2.2, 95%CI 1.2,3.9) guidelines than their high-income country (HIC) counterparts. Children who could go outside during COVID-19 were more likely to meet all WHO Global guidelines (AdjOR = 3.3, 95%CI 1.1,9.8) than those who were not. Children of parents with higher compared to lower stress were less likely to meet all three guidelines (AdjOR = 0.5, 95%CI 0.3,0.9). CONCLUSION: PA and SST levels of children from LMICs have been less impacted by COVID-19 than in HICs. Ensuring children can access an outdoor space, and supporting parents' mental health are important prerequisites for enabling pre-schoolers to practice healthy movement behaviours and meet the Global guidelines.

Objectively Measured Physical Activity and Sedentary Time among Children and Adolescents in Morocco: A Cross-Sectional Study.

BACKGROUND: Regular physical activity in childhood and adolescent plays an important role in reducing the risk of cardiovascular health diseases, diabetes, and obesity in adulthood. However, little is known about physical activity levels (PA) and sedentary time among children and adolescents in Morocco. OBJECTIVE: To examine gender, type of day, and age grade differences in objectively measured sedentary time, physical activity levels, and physical activity guideline attainment among children and adolescents in Morocco. METHOD: 172 children/adolescents (mean age = 10.92 ± 1.55 years, 49.4% are boys) were recruited for this study and wore a tri-axial accelerometer (GT3X+) for 7 consecutive days. Time spent in sedentary, PA levels, and daily steps were measured and compared according to gender, age grade, and the type of day (weekdays/weekends). RESULTS: In weekdays children/adolescents spent more time in sedentary than weekends (p < 0.001). Boys were eight times more likely to meet the recommendation for at least 60 min of moderate to vigorous physical activity per day than girls (OR: 8.569; 95% [CI]: 4.23-17.32), p < 0.001. CONCLUSION: These findings highlight the need for effective and sustainable strategies and programs aiming to promote physical activity and to reduce sedentary behavior among children and adolescents in Morocco.

Development and validation of bioelectrical impedance analysis equations for prediction total body water and fat-free mass using D2O technique in Moroccan children aged between 8 and 11 years old.

BACKGROUND/OBJECTIVES: Estimating body composition using bioelectric impedance analysis (BIA) requires specific prediction equations. The purpose of our study was to examine the validity of published BIA equations for assessing total body water (TBW) and fat-free mass (FFM) using deuterium oxide dilution (D2O) as a reference method and to develop new FFM and TBW BIA equations if needed for Moroccan pre-pubertal children. SUBJECTS/METHODS: Data were collected from 247 schoolchildren aged 8-11 years old. Children were sorted by gender and age group and assigned in development and validation groups. D2O dilution was used as reference method for estimating TBW and FFM. Bland and Altman test, effect size, pure error, and proportional bias were used to assess the reliability of previous published equations. Cross-validation was performed by Bland and Altman test and BIA new equations were developed by linear regression. RESULTS: Previously published equations were tested and showed significant bias values indicating that if used they would provide biased values of TBW and FFM. The new prediction equations developed were: [Formula: see text] (l) = 0.269 + 0.292 Ht2/R (cm2/Ω) + 0.221 weight (kg) + 0.824 sex (boys = 1, girls = 0) + 0.291 age (years) (R2 = 0.91, RMSE = 1.54 kg); [Formula: see text] (kg) = -0.450 + 0.380 Ht2/R (cm2/Ω) + 0.291 weight (kg) + 1.294 sex (boys = 1, girls = 0) + 0.446 age (years) (R2 = 0.91, RMSE = 1.97 kg). These equations provide better values of proportional bias, agreement, and pure error than the other tested equations. CONCLUSIONS: The new BIA prediction equations seem to be the most accurate for Moroccan pre-pubertal children.