OBJECTIVE:To examine the associations between BMI trajectories and changes in fat-free mass index (FFMI) and fat mass index (FMI), assessed via bioelectrical impedance analysis (BIA) and skinfold thickness (ST). METHODS:The study included 4708 European children with BIA data and 3627 with ST data, aged 2-9.9 years at baseline, participating in two waves of the IDEFICS (IDEFICS (Identification and Prevention of Dietary- and Lifestyle-Induced Health Effects in Children and Infants))/I.Family (I. Family (Determinants of eating behavior in European children, adolescents, and their parents)) studies (w0: 2007/08; w2: 2013/14). Children were classified into three BMI trajectory groups: retained normal weight (RNW), remained overweight/obese (ROO), and excessive weight gain (EWG). Analyses of covariance evaluated differences in BMI z-score changes, FFMI, and FMI across groups. Mixed-effects linear regression assessed associations between BMI z-score changes and FFMI/FMI over time. RESULTS:BMI z-score changes were more strongly associated with FMI (β = 1.16-1.70 in boys; 1.17-1.62 in girls, p < 0.05) than with FFMI, for both BIA and ST. In ROO and EWG groups, associations with FMI were consistently stronger, except among girls <6 years in the ROO group (BIA). In the RNW group, boys >6 years showed stronger associations with FFMI. CONCLUSIONS:Associations between BMI changes and FFMI/FMI vary by BMI trajectory and body composition method. BIA showed closer alignment with BMI changes than ST. These findings suggest that BMI alone may not adequately capture changes in specific body compartments. While convenient, BMI should be interpreted with caution, especially when fat or fat-free mass plays a differential role in disease risk or health outcomes.

Background and aims: Early life factors have been suggested to be associated with later cardiometabolic risk in children, adolescents and adults. Our study aimed to investigate the associations between early life factors and metabolic syndrome (MetS) in children and adolescents. Methods and results: Our analysis sample comprised of 8852 children aged 2-9 years at baseline that participated in up to three examination waves of the pan-European IDEFICS/I.Family cohort (baseline: 2007/08, 1st follow-up 2009/10, 2nd follow-up 2013/14). Mixed-effects models were used to estimate the associations between early life factors and MetS score and z-scores of waist circumference (WC), systolic (SBP) and diastolic blood pressure (DBP), Homeostasis Model Assessment for Insulin Resistance, high density lipoprotein cholesterol (HDL) and triglycerides. Being born large for gestational age (LGA) showed a positive association with MetS score ((3 = 0.67; 99%CI 0.44, 0.90) and with WC z-score ((3 = 0.51; 99%CI 0.39, 0.63) and was weakly inversely associated with HDL z-score. Being born small for gestational age (SGA) was associated with lower WC z-score (ss =-0.26; 99%CI-0.37,-0.16), with a lower MetS score (ss =-0.13; 99%CI-0.33, 0.08) and slightly higher z-scores of SBP and DBP. Weight gain during pregnancy was positively associated with MetS score and WC z-score while premature birth was positively associated with SBP. Conclusions: Children born LGA, SGA or preterm may warrant closer monitoring to prevent MetS later on.

Unhealthy food cues are omnipresent and promote overconsumption. Although childhood obesity rates are increasing, there is no strict regulation of the marketing of unhealthy foods towards children. This is problematic since the human brain, especially areas important for cognitive control, continues to develop into the 30s. It is not known in how far the brain response to unhealthy food cues varies with body mass index (BMI) and age. To investigate this, 168 children (10-17 y) and 182 adults (30-67 y) from the European IDEFICS cohort were scanned with the use of fMRI while viewing pictures of healthy and unhealthy foods. Children exhibited lower activation in the right dorsolateral prefrontal cortex (dlPFC) compared to adults when exposed to unhealthy food cues. Across all age groups, individuals with higher BMI demonstrated reduced activation in the middle cingulum in response to unhealthy food stimuli. Lastly, the relation between BMI and brain activation in response to unhealthy compared with healthy food stimuli varied with development: in children, higher BMI was correlated with decreased activation in right anterior insula and right dlPFC, whereas no such relationship was observed in adults. These findings suggest that children with higher BMI may be particularly vulnerable to unhealthy food cues. In this light, the lack of regulation regarding unhealthy food marketing targeted at children is concerning, especially considering the global increase in obesity rates.

It remains unclear how serum 25-hydroxyvitamin D (25(OH)D) concentrations relate to childhood bone health. We hypothesized that 25(OH)D was inversely associated with bone turnover biomarkers and positively associated with bone stiffness. Cross-sectional analyses were performed using data from participants (2-15-year-old, 51% boys) from the Identification and Prevention of Dietary- and Lifestyle-induced Health Effects in Children and Infants Study (IDEFICS)/I.Family cohort, comprising 3,638 serum 25(OH)D measurements collected in 2007-2008 and 2012-2013 across eight European countries. A biomarker of bone forma- tion (serum osteocalcin), a biomarker of bone resorption (serum C-terminal telopeptides of type I collagen [CTx]), and stiffness index measured using calcaneal quantitative ultra- sound were considered outcomes. Linear mixed-effects models were used to adjust for con- founders (i.e., age, sex, parental education, time spent in sports club, dairy products con- sumption, sedentary behavior, height and weight z-scores), the cluster effect of country and repeated measurements. Interactions of calcium intake, moderate-to-vigorous physical ac- tivity (MVPA) and weight status with 25(OH)D on outcomes were tested. Only 1 in 3 partic- ipants reached the sufficient 25(OH) D concentration of 20 ng/mL. Sufficient 25(OH)D was associated with higher stiffness index if participants had MVPA >= 60 min/day (beta= 12.14, P < .05). Moreover, 25(OH)D was inversely associated with CTx (beta= -7.09, P < .05); this associa- tion was positive but not statistically significant among primary school children living with overweight/obesity. No interaction was observed for calcium intake. In conclusion, serum 25(OH)D and CTx were inversely associated. MVPA interacted with the positive association between 25(OH)D and bone stiffness, highlighting the importance of promoting MVPA guide- lines in future vitamin D and bone health interventions. (c) 2024 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

Unhealthy food cues are omnipresent and promote overconsumption. Although childhood obesity rates are increasing, there is no strict regulation of the marketing of unhealthy foods towards children. This is problematic since children’s brains, especially areas important for cognitive control, do not mature until their early 20s. It is not known in how far the brain response to unhealthy food cues varies with body mass index and age. To investigate this, 168 children (10-17 y; 71 prepubertal children, 97 pubertal children) and 182 adults (30-67 y) from the European IDEFICS cohort were scanned with fMRI while viewing pictures of healthy and unhealthy foods. Pubertal children exhibited lower activation in the right dorsolateral prefrontal cortex (dlPFC) compared to adults when exposed to unhealthy food cues. Across all age groups, individuals with higher body mass demonstrated reduced activation in the middle cingulum in response to unhealthy food stimuli. Lastly, the relation between body mass index and brain activation in response to unhealthy compared with healthy food stimuli varied with development: in prepubertal children, higher body mass index was correlated with decreased activation in right anterior insula and right dlPFC, whereas no such relationship was observed in pubertal children or adults. These findings suggest that pubertal children and prepubertal children with higher body mass index may be particularly vulnerable to unhealthy food cues. In this light, the lack of regulation regarding unhealthy food marketing targeted at is concerning, especially considering the global increase in obesity rates.

PurposeIt is assumed that sensory taste perception shapes food choices and impacts dietary intake. However, this has rarely been studied in free living subjects of different age-groups with standardised methods. The present study investigated the association of the ability to rank sweet and fat taste intensities with consumption frequency of sweet and fatty foods in children, adolescents and adults from eight European countries.MethodsIn total, 461 children, 421 adolescents and 612 adults from the IDEFICS/I.Family cohort participated in sensory sweet and fat intensity rating tests. Sweet and fatty food consumption frequencies were assessed using a food frequency questionnaire. The association between the ability to rank sweet and fat intensity with sweet and fatty food consumption frequencies was estimated using linear mixed regression models adjusting for weight status, country, sex, age and family affiliation.ResultsAcross all age groups, the largest proportion of participants had medium sweet and fat taste intensity ranking abilities. The next largest proportion had low sweet and fat taste intensity rating abilities, while the smallest proportion had high intensity rating abilities to sweet and fat taste. A negative association of sweet and fat taste intensity ranking ability with sweet and fatty food consumption frequencies was found for children. In adolescents, the association was positive. In adults, there was no association.ConclusionIt seems that the association of taste intensity ratings with food consumption frequencies during adolescence differs from the associations in children and adults. This could be due to hormonal changes during puberty, growth and maturation. Thus, further research focussing on maturation processes in association with taste perception during adolescence may be required.

BACKGROUND:Reference values of ferritin and transferrin for European children do not exist. OBJECTIVE:We aimed to provide sex-, age-, and body mass index (BMI)-specific serum ferritin and transferrin reference percentiles of 3-15-y-old children based on cohort data and to investigate determinants of iron status. METHODS:A total of 3390 ferritin and 3416 transferrin measurements from children residing in 8 European countries participating in the IDEFICS/I.Family cohort (https://www.isrctn.com/ISRCTN62310987) at baseline (W0) and 6 y later (W3) were used to estimate percentiles using the generalized additive model for location, scale and shape. Associations of serum ferritin and transferrin concentrations with total iron intake, total iron intake additionally adjusted for vitamin C intake, and iron from heme sources were investigated separately with adjustment for sex, age, country of residence, parental education, usual energy intake and BMI z-score in regression models using cross-sectional and longitudinal data. RESULTS:The age-specific ferritin and transferrin 5th and 95th reference percentiles ranged from 10.9 to 81.1 μg/L and 2.23 to 3.56 g/L, respectively. A deficient iron status was observed in 3% of children at W0 and 7% of children and adolescents at W3, respectively. At both waves, a higher iron intake from heme sources was positively associated with serum ferritin {W0: β = 3.21 [95% confidence interval (CI): 0.71, 5.71]; W3: β = 4.48 [95% CI: 2.09, 6.87]}, that is, children consuming one mg more heme iron had a 3.21 and 4.48 μg/L higher ferritin concentration. Adherence to a mainly vegetarian diet was associated with a lower chance for sufficient serum ferritin cross-sectionally at W3 [odds ratio (OR) 0.40 (95% CI: 0.21, 0.81)] and longitudinally [OR 0.35 (95% CI: 0.15, 0.93)]. CONCLUSIONS:Age-, sex-, and BMI-specific reference percentiles of serum ferritin and transferrin concentrations based on cohort data are provided for European children aged 3-15 y and may be used in clinical practice.

CONTEXT:Vitamin D status has previously been associated with cardiometabolic risk markers in children and adolescents. In particular, it has been suggested that children with obesity are more prone to vitamin D deficiency and unfavorable metabolic outcomes compared with healthy-weight children.OBJECTIVE:To conduct a longitudinal study assessing this association in children and stratify by body mass index (BMI) category.METHODS:Children from the pan-European IDEFICS/I.Family cohort with at least one measurement of serum 25-hydroxyvitamin D [25(OH)D] at cohort entry or follow-up (n = 2171) were included in this study. Linear mixed-effect models were used to assess the association between serum 25(OH)D as an independent variable and z-scores of cardiometabolic risk markers (waist circumference, systolic [SBP] and diastolic blood pressure [DBP], high- [HDL] and low-density lipoprotein, non-HDL, triglycerides [TRG], apolipoprotein A1 [ApoA1] and ApoB, fasting glucose [FG], homeostatic model assessment for insulin resistance [HOMA-IR], and metabolic syndrome score) as dependent variables.RESULTS:After adjustment for age, sex, study region, smoking and alcohol status, sports club membership, screen time, BMI, parental education, and month of blood collection, 25(OH)D levels were inversely associated with SBP, DBP, FG, HOMA-IR, and TRG. The HOMA-IR z-score decreased by 0.07 units per 5 ng/mL increase in 25(OH)D. The 25(OH)D level was consistently associated with HOMA-IR irrespective of sex or BMI category.CONCLUSION:Low serum 25(OH)D concentrations are associated with unfavorable levels of cardiometabolic markers in children and adolescents. Interventions to improve vitamin D levels in children with a poor status early in life may help to reduce cardiometabolic risk.

Dietary diversity (DD) plays a crucial role in fostering high-quality diets, but its association with health outcomes, particularly body adiposity and non-communicable diseases (NCDs), is inconsistent. This may be due to a lack of a standardized method for estimating DD. Our study investigates the association between two DD indices, namely the dietary diversity score (DDS) and food variety score (FVS), and anthropometric measures, biochemical parameters, and diet quality in a large population sample from the I.Family study across research centers in eight European countries. In our cross-sectional analysis of 3035 participants, DDSs varied among countries, with a higher prevalence in the third DDS tertile among those with higher education. DDS showed a positive association with diet quality across all age groups. Higher DDS tertile individuals showed increased fiber, fruit, and vegetable intake, greater meal frequency, and lower ultra-processed food consumption. No relevant biochemical differences were observed across DDS tertiles, and a higher DDS was associated with lower overweight/obesity prevalence only in adults. No significant associations were found with FVS. Our findings emphasize the need to consider food groups for a more accurate estimation of diet quality. This aligns with studies suggesting DDS alone is not an independent risk factor for obesity in children and adolescents. Public health programs should prioritize food diversity to promote improved nutrition and overall well-being in communities.

The digital environment can pose health risks through exposure to unhealthy content. Yet, little is known about its relation to children’s cognitive functioning . This study investigates the association between digital media (DM) exposure and children’s cognitive functioning. This cross-sectional study is based on examinations of children aged 8–18 years (N = 8673) of the I.Family cohort (2013–2014). Exposure to television, computer, smartphone and internet was self-reported (hours/day). Media multitasking (MMT) was defined as simultaneous use of computers with other digital or non-screen-based activities. Standard instruments were used to assess cognitive inflexibility (score: 0–39), decision-making ability (− 100 to + 100) and impulsivity (12–48). Adjusted regression coefficients and 99.9%CIs were calculated by generalized linear mixed-effects models. In total, 3261 participants provided data for impulsivity, 3441 for cognitive inflexibility and 4046 for decision-making. Exposure to smartphones and media multitasking were positively associated with impulsivity (β smartphone = 0.74; 99.9%CI = 0.42–1.07; β MMT = 0.73; 99.9%CI = 0.35–1.12) and cognitive inflexibility (β smartphone = 0.32; 99.9%CI = -0.02–0.66; β MMT = 0.39; 99.9%CI = 0.01–0.77) while being inversely associated with decision-making ability. Extensive smartphone/internet exposure combined with low computer/medium TV exposure was associated with higher impulsivity and cognitive inflexibility scores, especially in girls. DM exposure is adversely associated with cognitive functioning in children and adolescents. Children require protection against the likely adverse impact of digital environment.

Background Dental caries is a multifactorial disease that is highly dependent on diet, where a lower consumption and intake frequency of sugar would be favorable. The aims were (i) to examine dietary intake and meal patterns, more specifically sugar intake and foods high in sugar, among young adults with high caries activity, and (ii) to investigate the association between dietary and meal patterns consumption, and level of caries activity. Methods This study presents baseline data from an ongoing randomized controlled trial. A total of 50 young adults (aged 23.0 ± 3.0 years) with ≥ 2 decayed tooth surfaces were included. Dietary intake was captured with a 59-item food frequency questionnaire (FFQ) and a three-day food diary. Adherence to dietary guidelines was analyzed by comparing the dietary intake to the Nordic Nutritional Recommendations (NNR) 2012 and by using the Healthy Dietary Adherence score (HDAS). Participants were categorized into two groups: (i) the Caries group with 2–4 decayed surfaces, and (ii) the High caries group with ≥ 5 decayed surfaces. Results The High caries group reported a statistically significantly higher snack and total meal intake compared to the Caries group, as well as a sugar intake exceeding the Nordic nutritional recommendations. The majority of the participants reported a high intake frequency (> 2.5/day) of sweet foods and drinks and less than one intake of fruit and vegetables, respectively, per day. Similar results were found when analyzing adherence by using the HDAS, where the lowest adherence according to dietary guidelines was shown for the food groups of sugar, whole meal products, and fruit and vegetables. Conclusion The results indicated a high intake of sugar and low intake of fruit, vegetables, and fiber in high caries-active individuals.

Abstract Background This study aimed to examine associations of early childhood physical fitness and physical activity (PA) with PA during later childhood/early adolescence while accounting for gender differences. Methods We selected data of N = 4329 children from the IDEFICS/I. Family cohort (age 2.4–11.7 years) with data on baseline fitness and accelerometer measurements. At baseline, physical fitness tests were conducted including Flamingo balance, Backsaver sit and reach, Handgrip strength, Standing Long Jump, 40-m sprint and 20-m Shuttle run (to estimate cardio-respiratory fitness levels). PA was measured with Actigraph accelerometers over 3 days at baseline (ActiTrainer or GT1M) and 7 days at follow-up (GT3X). Evenson cutpoints were used to determine moderate-to-vigorous PA (MVPA) time, and children with ≥60mins/day of average MVPA were deemed as having met WHO guidelines at baseline and follow-up. Linear and logistic regressions were performed to examine longitudinal associations between meeting WHO guidelines, MVPA, and physical fitness tests at baseline with meeting WHO guidelines and MVPA at follow-up. Models were conducted on the entire sample, the sex-stratified sample, and stratified by sex and pubertal status at follow-up. Results Results showed that meeting WHO guidelines for MVPA at baseline was positively associated with MVPA (Standardized Beta (B) = 0.13, 95%CI:(5.6;11.1)) and meeting WHO guidelines at follow-up for the entire sample (OR = 2.1, 95%CI:(1.5; 3.14), and stratified by males (OR = 2.5, 95%CI:(1.5; 4.1)) and females (OR = 1.8, 95%CI:(1.0; 3.2)). This was also found for both male pre/early pubertal and pubertal groups but only in the female pre/early pubertal group, and not the female pubertal group (MVPA: B = .00, 95%CI:(− 6.1; 5.6), WHO: OR = 0.61, 95%CI:(0.23;1.6)). Models indicated that Standing Long jump, 40-m sprint, Shuttle run and Flamingo balance at baseline were associated with MVPA and meeting the guidelines at follow-up. Conclusions Meeting WHO guidelines and certain fitness tests at baseline were strongly associated with MVPA and meeting WHO guidelines at follow-up, but this association varied with sex and pubertal status. Consequently, these findings underline the importance of ensuring sufficient physical activity in terms of quality and quantity for children at the earliest stages of life. Trial registration ISRCTN62310987.

Increasing data suggest that overnutrition-induced obesity may trigger an inflammatory process in adipose tissue and upturn in the innate immune system. Numerous players have been involved in governing the inflammatory response, including epigenetics. Among epigenetic players, miRNAs are emerging as crucial regulators of immune cell development, immune responses, autoimmunity, and inflammation. In this study, we aimed at identifying the involvement of candidate miRNAs in relation to inflammation-associated biomarkers in a subsample of European children with overweight and obesity participating in the I.Family study. The study sample included individuals with increased adiposity since this condition contributes to the early occurrence of chronic low-grade inflammation. We focused on the acute-phase reagent C-reactive protein (CRP) as the primary outcome and selected cytokines as plausible biomarkers of inflammation. We found that chronic low-grade CRP elevation shows a highly significant association with miR-26b-3p and hsa-miR-576-5p in boys. Furthermore, the association of CRP with hsa-miR-10b-5p and hsa-miR-31-5p is highly significant in girls. We also observed major sex-related associations of candidate miRNAs with selected cytokines. Except for IL-6, a significant association of hsa-miR-26b-3p and hsa-miR-576-5p with TNF-α, IL1-Ra, IL-8, and IL-15 levels was found exclusively in boys. The findings of this exploratory study suggest sex differences in the association of circulating miRNAs with inflammatory response biomarkers, and indicate a possible role of miRNAs among the candidate epigenetic mechanisms related to the process of low-grade inflammation in childhood obesity.

Background In recent years, the exciting emergence of circulating miRNAs as stable, reproducible, and consistent among individuals has opened a promising research opportunity for the detection of non-invasive biomarkers. A firm connection has been established between circulating miRNAs and glycaemic as well as metabolic homeostasis, showing that levels of specific miRNAs vary under different physio-pathological conditions. Objective In this pilot study, we investigated the expression of candidate miRNAs, hsa-miR-191-3p and hsa-miR-375, in relation to biomarkers associated with insulin sensitivity in a subgroup (n=58) of subjects participating to the European I.Family Study, a project aimed to assess the determinants of eating behaviour in children and adolescents and related health outcomes. The sample included overweight/obese children/adolescents since overweight/obesity is a known risk factor for impaired glucose homeostasis and metabolic disorders. Biological targets of candidate miRNAs were also explored in silico. Results We observed a significant association of the two miRNAs and early changes in glycaemic homeostasis, independent of covariates including country of origin, age, BMI z-score, puberty status, highest educational level of parents, total energy intake, energy from fats, energy from carbohydrates, and energy from proteins. Conclusion Identification of circulating miRNAs associated with insulin impairment may offer novel approaches of assessing early variations in insulin sensitivity and provide evidence about the molecular mechanisms connected to early changes in glycaemic homeostasis. Trial registration ISRCTN, ISRCTN62310987. Retrospectively registered, http://isrctn.com/ISRCTN62310987

Abstract Background Media use may influence metabolic syndrome (MetS) in children. Yet, longitudinal studies are scarce. This study aims to evaluate the longitudinal association of childhood digital media (DM) use trajectories with MetS and its components. Methods Children from Belgium, Cyprus, Estonia, Germany, Hungary, Italy, Spain and Sweden participating in the IDEFICS/I.Family cohort were examined at baseline (W1: 2007/2008) and then followed-up at two examination waves (W2: 2009/2010 and W3: 2013/2014). DM use (hours/day) was calculated as sum of television viewing, computer/game console and internet use. MetS z-score was calculated as sum of age- and sex-specific z-scores of four components: waist circumference, blood pressure, dyslipidemia (mean of triglycerides and HDL-cholesterol−1) and homeostasis model assessment for insulin resistance (HOMA-IR). Unfavorable monitoring levels of MetS and its components were identified (cut-off: ≥ 90th percentile of each score). Children aged 2–16 years with ≥ 2 observations (W1/W2; W1/W3; W2/W3; W1/W2/W3) were eligible for the analysis. A two-step procedure was conducted: first, individual age-dependent DM trajectories were calculated using linear mixed regressions based on random intercept (hours/day) and linear slopes (hours/day/year) and used as exposure measures in association with MetS at a second step. Trajectories were further dichotomized if children increased their DM duration over time above or below the mean. Results 10,359 children and adolescents (20,075 total observations, 50.3% females, mean age = 7.9, SD = 2.7) were included. DM exposure increased as children grew older (from 2.2 h/day at 2 years to 4.2 h/day at 16 years). Estonian children showed the steepest DM increase; Spanish children the lowest. The prevalence of MetS at last follow-up was 5.5%. Increasing media use trajectories were positively associated with z-scores of MetS (slope: β = 0.54, 95%CI = 0.20–0.88; intercept: β = 0.07, 95%CI = 0.02–0.13), and its components after adjustment for puberty, diet and other confounders. Children with increasing DM trajectories above mean had a 30% higher risk of developing MetS (slope: OR = 1.30, 95%CI = 1.04–1.62). Boys developed steeper DM use trajectories and higher risk for MetS compared to girls. Conclusions Digital media use appears to be a risk factor for the development of MetS in children and adolescents. These results are of utmost importance for pediatricians and the development of health policies to prevent cardio-metabolic disorders later in life. Trial registration ISRCTN, ISRCTN62310987 . Registered 23 February 2018- retrospectively registered.

Background: Childhood overweight is an increasing public health concern and has recently been associated with the consumption of a traditional Swedish milk cereal drink (MCD). This study aimed to describe the consumption pattern of MCD among study participants in relation to the recommendations by the National Food Agency of Sweden. Method: A cross-sectional study among the Swedish cohort of the IDEFICS.Family (I.Family) study was conducted in 2013/2014. Swedish participants completed a questionnaire aimed at understanding the prevalence of consumption, timing, frequency, feeding modality and rationale for offering MCD. Results: Most children (74.7%) reportedly consumed MCD. Of those who consumed MCD, a large part of the participants consumed MCD two or more times a day with a high proportion of participants (87%) stating a preference for bottle-feeding. Keywords: Milk cereal drink, Obesity, Complementary food, Feeding practice, I. Family Study, Sweden.

Background Since only few longitudinal studies with appropriate study designs investigated the relationship between objectively measured physical activity (PA) and overweight, the degree PA can prevent excess weight gain in children, remains unclear. Moreover, evidence is limited on how childhood overweight determines PA during childhood. Therefore, we analyzed longitudinal trajectories of objectively measured PA and their bi-directional association with weight trajectories of children at 2- and 6-year follow-ups. Methods Longitudinal data of three subsequent measurements from the IDEFICS/I.Family cohort study were used to analyze the bi-directional association between moderate-to-vigorous PA (MVPA) and weight status by means of multilevel regression models. Analyses comprised 3393 (2-year follow-up) and 1899 (6-year follow-up) children aged 2–15.9 years from eight European countries with valid accelerometer data and body mass index (BMI) measurements. For categorized analyses, children’s weight status was categorized as normal weight or overweight (cutoff: 90th percentile of BMI) and children’s PA as (in-) sufficiently active (cutoffs: 30, 45 and 60 min of MVPA per day). Results Children engaging in at least 60 min MVPA daily at baseline and follow-ups had a lower odds of becoming overweight (odds ratio [OR] at 2-year follow-up: 0.546, 95% CI: 0.378, 0.789 and 6-year follow-up: 0.393, 95% CI: 0.242, 0.638), compared to less active children. Similar associations were found for 45 min MVPA daily. On the other side, children who became overweight had the lowest odds to achieve 45 or 60 min MVPA daily (ORs: 0.459 to 0.634), compared to normal weight children. Conclusions Bi-directional associations between MVPA and weight status were observed. In summary, at least 60 min MVPA are still recommended for the prevention of childhood overweight. To prevent excess weight gain, 45 min MVPA per day also showed preventive effects.

Background/objectives To provide age- and sex-specific percentile curves of serum 25-hydroxyvitamin D (25(OH)D) by determinants from 3-<15 year-old European children, and to analyse how modifiable determinants influence 25(OH)D. Subjects/methods Serum samples were collected from children of eight European countries participating in the multicenter IDEFICS/I.Family cohort studies. Serum 25(OH)D concentrations were analysed in a central lab by a chemiluminescence assay and the values from 2171 children ( N = 3606 measurements) were used to estimate percentile curves using the generalized additive model for location, scale and shape. The association of 25(OH)D with time spent outdoors was investigated considering sex, age, country, parental education, BMI z score, UV radiation, and dietary vitamin D in regressions models. Results The age- and sex-specific 5th and 95th percentiles of 25(OH)D ranged from 16.5 to 73.3 and 20.8 to 79.3 nmol/l in girls and boys, respectively. A total of 63% had deficient (<50 nmol/l), 33% insufficient (50-<75 nmol/l) and 3% sufficient (≥75 nmol/l) levels. 25(OH)D increased with increasing UV radiation, time spent outdoors, and vitamin D intake and slightly decreased with increasing BMI z score and age. The odds ratio (OR) for a non-deficient 25(OH)D status (reference category: deficient status) by one additional hour spent outdoors was 1.21, 95% CI [1.12–1.31], i.e., children who spent one more hour per day outdoors than other children had a 21% higher chance of a non-deficient than a deficient status. Conclusion A majority of children suffer from deficient 25(OH)D. UV radiation, outdoor time, and dietary vitamin D are important determinants of 25(OH)D.

Muscular and cardiorespiratory fitness (MF and CRF) have been related to inflammation. Thus, the aim of this study was to assess the relationship between fitness and high-sensitivity C-reactive protein (hs-CRP) in European children both in the cross-sectional and longitudinal analysis. Three hundred and fifty-seven children (46.2% males) aged 2–9 years with hs-CRP measured, data from MF and CRF, diet quality, objectively measured physical activity (PA) and screen time at baseline and follow-up after 2 years were included. Body mass index z-score (zBMI), waist circumference (WC) and fat mass index (FMI) were assessed. MF and CRF were also dichotomized as follows: low-medium quartiles (Q1–Q3) and highest quartile (Q4). At follow-up, children with the highest CRF (Q4) showed a lower probability of having high hs-CRP. In the longitudinal analysis, children who improved their CRF over time showed a significantly lower probability (p < 0.05) of being in the highest hs-CRP category at follow-up, independently of the body composition index considered: odds ratio (OR) = 0.22 for zBMI, OR = 0.17 for WC, and OR = 0.21 for FMI. Improving CRF during childhood reduces the odds of an inflammatory profile, independently of body composition and lifestyle behaviours. These highlight the importance of enhancing fitness, especially CRF, to avoid an inflammatory state in children.