Physical Activity and Skipping Breakfast Have Independent Effects on Body Fatness Among Adolescents.

OBJECTIVE: We analyzed the longitudinal relationship between breakfast intake and adiposity among adolescents, and the possible mediation role of physical activity on this phenomenon. METHODS: We conducted the longitudinal study composed of 86 adolescents (11-14 years old), absence of any known chronic diseases and no regular medicine use that returned the formal consent and assent both signed. Breakfast intake was reported through face-to-face interviews. Adiposity was assessed using a densitometry scanner. Physical activity was estimated through step counts performed using pedometers. Biological maturation was estimated through the maturity level. Student t test for independent samples was used to compare adolescents who were "nonskipping breakfast" and "skipping breakfast," whereas the relationship between adiposity, physical activity, and skipping breakfast was assessed using Pearson correlation. Structural equation model was created to identify the mediation role of physical activity on the relationship between nonskipping breakfast and adiposity. RESULTS: After 12 months, adolescents who had consumed breakfast regularly presented decreased trunk fatness (-3.5% [95% confidence interval (CI): -6.9 to -0.2]) and body fatness (-2.3% [95% CI: -3.9 to -0.7]) compared with their counterparts. Physical activity had an inverse relationship with trunk fatness (r = -0.270 [95% CI: -0.457 to -0.060]). Nonskipping breakfast was, however, not significantly related to trunk fatness; however, physical activity seems to reduce trunk fatness in our sample (r = -0.281; 95% CI: -0.479 to -0.083). CONCLUSIONS: Adolescents who ate breakfast regularly presented lower body fatness independent of physical activity, whereas trunk fatness decreased in adolescents who improved physical activity.

Changes in body fatness affect cardiovascular outcomes more than changes in physical activity.

OBJECTIVE: The aim of this study was to analyse whether changes in physical activity and body fatness are related to modifications in cardiovascular risk factors among adolescents. Material and methods A sample of 89 healthy adolescents was recruited for this study. We assessed habitual physical activity, body fat percentage, arterial thickness, blood sample, and biological maturation. Multivariate models were used to analyse the relationships between independent and dependent variables. RESULTS: Physical activity (mean difference: 429.4 steps [95% confidence interval=-427 to 1286]) and body fatness (mean difference: -0.7% [95% confidence interval=-1.6-0.2]) remained stable during the study period. Independent of changes in physical activity, for each percentage increase in body fatness, femoral intima-media thickness increased by 0.007 mm (ß=0.007 [95% confidence interval=0.001-0.013]). Longitudinal relationships were found for high-density lipoprotein-cholesterol (ß=-0.477 mg/dl [95% confidence interval=-0.805 to -0.149]) and triacylglycerol (ß=2.329 mg/dl [95% confidence interval=0.275-4.384]). CONCLUSION: Changes in body fatness are more important than the amount of physical activity on cardiovascular and metabolic risks.

Cardiovascular and metabolic risk markers are related to parasympathetic indices in pre-pubertal adolescents.

OBJECTIVE: To analyse the relationship between different heart rate variability indices, resting heart rate, and cardiovascular markers in adolescents. METHODS: A cross-sectional study was carried out with information from an ongoing cohort study. The sample was composed of 99 adolescents who complied with the following inclusion criteria: aged between 11 and 14 years; enrolled in a school unit of elementary education; absence of any known diseases; no drug consumption; and a formal consent signed by the parents or legal guardians. Weight, height, heart rate variability, lipid profile, inflammatory markers, blood pressure, resting heart rate, intima-media thickness, blood flow, and trunk fatness were measured. Partial correlation and linear regression (expressed by ß and 95% confidence intervals [95%CI]) analyses were used to analyse the relationships between the variables. RESULTS: In the linear regression analysis, even after adjustments for sex, age, trunk fatness, and somatic maturation, parasympathetic activity presented significant correlations with maximum carotid artery blood flow (ß=-0.111 [95%CI=-0.216; -0.007]), systolic blood pressure (ß=-0.319 [95%CI=-0.638; -0.001]), and resting heat rate (ß=-0.005 [95%CI=-0.009; -0.002]). CONCLUSION: Parasympathetic activity at rest is inversely related to maximum and minimum blood flow, triacylglycerol levels, and systolic blood pressure. These findings suggest that heart rate variability has the potential to discriminate pre-pubertal adolescents at increased risk.

Breakfast frequency, adiposity, and cardiovascular risk factors as markers in adolescents.

OBJECTIVE: To analyse the relationship between skipping breakfast and haemodynamic, metabolic, inflammatory, and cardiovascular risk factors in adolescents. METHODS: A cross-sectional study was carried out with information from an ongoing cohort study in Presidente Prudente, São Paulo, Brazil. The sample comprised of 120 adolescents (11.7±0.8 years old) who met the following inclusion criteria: age between 11 and 14 years; enrolled in the school unit of elementary education; absence of any known disease; and no drug consumption. The parents or legal guardians of the patients signed a formal informed consent. Skipping breakfast was self-reported through face-to-face interviews. Blood pressure, intima-media thickness, trunk fatness, total and fractional cholesterol levels - high-density lipoprotein cholesterol and low-density lipoprotein cholesterol - triacylglycerol levels, and high-sensitivity C-reactive protein levels were measured. RESULTS: In this study, 47.5% (95% CI: 38.5-56.4%) of the adolescents reported skipping breakfast at least 1 day/week. Adolescents who skipped breakfast had higher values of trunk fatness and systolic blood pressure. Breakfast frequency was negatively related to systolic blood pressure (ß -1.99 [-3.67; -0.31]) and z score dyslipidaemia (ß -0.46 [-0.90; -0.01]), but this relationship was mediated by trunk fatness. CONCLUSION: Skipping breakfast is related to cardiovascular risk factors in adolescents, and this relationship was mainly mediated by trunk fatness.

Morphological and metabolic determinants of nonalcoholic fatty liver disease in obese youth: a pilot study.

BACKGROUND: Nonalcoholic fatty liver disease (NAFLD) related to obesity has been rising in the last decades, though the morphological and metabolic determinants are remain unclear in children. The aim of this study was to analyze the morphological determinants and metabolic abnormalities in obese children and adolescents, classified either as with (P-NAFLD) or without (N-NAFLD). The sample comprised 190 individuals, aged 6 to 16 years-old, assigned into one of 4 groups according to sex and presence or absence of NAFLD. Obesity was obtained according to body mass index (BMI) cut-points. Body composition variables was estimated by Dual-Energy X-ray Absorptiometry (DEXA). Total cholesterol (TC), triglycerides (TG), HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C), insulin, fasting glucose (FG) and blood pressure were also analyzed. The diagnosis of NAFLD, as well as the measurement of intra-abdominal fat tissue thickness (IAF) and subcutaneous abdominal fat tissue thickness (SCF), was carried-out by ultrasound. RESULTS: Males and females belonging to P-NAFLD group showed, respectively, higher TFM and IAF. When data were adjusted for sex, age and total fat mass, those in P-NAFLD showed statistically higher IAF, TFM and TG. CONCLUSION: Our study showed that obese youngsters who were assigned to P-NAFLD group were twice as likely to present higher concentration of triglycerides, higher levels of trunk fat, as well as intra-abdominal fat compared to their N-NAFLD counterparts even after adjustments for sex, age, pubertal stage and total body fat mass.

Resting heart rate as a predictor of metabolic dysfunctions in obese children and adolescents.

BACKGROUND: Recent studies have identified that a higher resting heart rate (RHR) is associated with elevated blood pressure, independent of body fatness, age and ethnicity. However, it is still unclear whether RHR can also be applied as a screening for other risk factors, such as hyperglycemia and dyslipidemia. Thus, the purpose of the presented study was to analyze the association between RHR, lipid profile and fasting glucose in obese children and adolescents. METHODS: The sample was composed of 180 obese children and adolescents, aged between 7-16 years. Whole-body and segmental body composition were estimated by Dual-energy X-ray absorptiometry. Resting heart rate (RHR) was measured by heart rate monitors. The fasting blood samples were analyzed for serum triglycerides, total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and glucose, using the colorimetric method. RESULTS: Fasting glucose, TC, triglycerides, HDL-C, LDL-C and RHR were similar in both genders. The group of obese subjects with a higher RHR presented, at a lower age, higher triglycerides and TC. There was a significant relationship between RHR, triglycerides and TC. In the multivariate model, triglycerides and TC maintained a significant relationship with RHR independent of age, gender, general and trunk adiposity. The ROC curve indicated that RHR has a high potential for screening elevated total cholesterol and triglycerides as well as dyslipidemia. CONCLUSION: Elevated RHR has the potential to identify subjects at an increased risk of atherosclerosis development.