The association between obesity and academic performance in youth: a systematic review.

Previous studies have found that obesity could influence academic performance. The aim of this study was to systematically review the scientific evidence on the association between obesity and academic performance in school children. A systematic review of English articles was undertaken by using databases PubMed/Medline, ERIC, LILACS, SciELO and Web of Science. Cross-sectional and longitudinal studies examining the association between obesity and academic performance in children and adolescents, published between January 1990 and December 2016, were included. Risk of bias was assessed by using Strengthening the Reporting of Observational Studies in Epidemiology. Thirty-four studies (23 cross-sectional and 11 longitudinal) matched all inclusion criteria and were included. Seven studies were classified as low risk of bias, 23 as medium risk and four as high risk. After controlling for covariates such as socio-economic status, parental education and physical activity, the association between obesity and academic performance becomes uncertain for most of the studies (55.9%). Therefore, at present, there is insufficient evidence to support a direct link between obesity and poor academic performance in school age children. In order to clarify this issue, we need more longitudinal studies with adequate sample sizes and that control for potential confounders.

Self-initiated changes in physical activity levels improve cardiometabolic profiles: A longitudinal follow-up study.

BACKGROUND AND AIMS: While studies have described the importance of higher physical activity levels (PAL) in weight loss, the impact of self-initiated PAL on health status warrants further study. We aimed to prospectively examine the effects of self-initiated longitudinal PAL changes on body mass index (BMI) and cardiometabolic parameters in normal weight, overweight and obese adults. METHODS AND RESULTS: We included 4840 adults (mean age 41.6 ± 7.9 years, 79% male) undergoing routine health screening examinations. Self-reported PAL, height, weight, blood pressure and blood samples were collected at baseline and after a mean (95% confidence interval) follow up of 536 (531-541) days. Subjects were stratified according to BMI [39.8% normal weight (<25 kg/m2), 45.1% overweight (25.0-29.9 kg/m2), and 19.1% obese (≥30 kg/m2)]. In normal weight individuals, BMI increased from baseline to follow-up, irrespective of PAL changes. On the other hand, overweight and obese individuals that increased PAL experienced a decrease in BMI by -0.9% and -3.1%, respectively (p < 0.05). Overweight and obese individuals that increased PAL also experienced a decrease in -5.8% -4.6% in non-HDL concentrations from baseline to follow-up (p < 0.05). Finally, in overweight individuals, LDL cholesterol concentrations decreased from baseline to follow-up, irrespective of PAL changes whereas in obese individuals, a maintenance or increased PAL were associated with a decrease in -4.7% and -6.1% (p < 0.05), respectively. CONCLUSIONS: In a large cohort of screening patients, longitudinal self-initiated PAL is associated with improved BMI and cardiometabolic profile in overweight and obese individuals.

Body composition of obese adolescents: association between adiposity indicators and cardiometabolic risk factors.

BACKGROUND: The association between obesity during adolescence and the increased risk of cardiometabolic diseases indicates the need to identify reproducible and cost effective methods for identifying individuals who are at increased risk of developing diseases. The present cross-sectional study investigated the occurrence of metabolic consequences of obesity in adolescents and the use of adiposity indicators as predictors of cardiometabolic risk. METHODS: A fasting blood sample was taken in 93 pubertal obese adolescents aged 13-18 years old (39 males, 54 females) for the assessment of cardiometabolic risk markers (glucose, lipid profiles, insulin resistence, and inflammatory and endothelial dysfunction markers). Together with anthropometry, total fat mass and lean mass were determined by dual-energy X-ray absorptiometry (DXA). RESULTS: The prevalence of dyslipidaemia and disorders in glucose metabolism are noticeably higher in the present study. There was no correlation between the percentage of body fat according to DXA and most indicators of adiposity. For boys, the arm circumference values predicted the increase in fasting insulin (r² = 0.200), homeostasis model assessment of insulin resistance (r² = 0.267) and cardiometabolic risk score (r² = 0.338). The percentage of body fat according to DXA predicted the inflammation score (r² = 0.172). For girls, body mass index was the parameter that best described the variability of fasting insulin (r² = 0.079) and inflammation score (r² = 0.263). The waist-to-stature ratio was able to predict the triglyceride values (r² = 0.090). CONCLUSIONS: Anthropometric measures of adiposity, such a body mass index, waist-to-stature ratio, arm circumference and waist circumference,should be considered in the clinical evaluation of obese adolescents.

Physical fitness and academic performance in youth: A systematic review.

Physical fitness (PF) is a construct of health- and skill-related attributes which have been associated with academic performance (AP) in youth. This study aimed to review the scientific evidence on the association among components of PF and AP in children and adolescents. A systematic review of articles using databases PubMed/Medline, ERIC, LILACS, SciELO, and Web of Science was undertaken. Cross-sectional and longitudinal studies examining the association between at least one component of PF and AP in children and adolescents, published between 1990 and June 2016, were included. Independent extraction of articles was carried out by the two authors using predefined data fields. From a total of 45 studies included, 25 report a positive association between components of PF with AP and 20 describe a single association between cardiorespiratory fitness (CRF) and AP. According to the Strengthening the Reporting of Observational Studies in Epidemiology guidelines: 12 were classified as low, 32 as medium risk, and 1 as high risk of bias. Thirty-one studies reported a positive association between AP and CRF, six studies with muscular strength, three studies with flexibility, and seven studies reported a positive association between clustered of PF components and AP. The magnitude of the associations is weak to moderate (ß = 0.10-0.42 and odds = 1.01-4.14). There is strong evidence for a positive association between CRF and cluster of PF with AP in cross-sectional studies; and evidence from longitudinal studies for a positive association between cluster of PF and AP; the relationship between muscular strength and flexibility with AP remains uncertain.

Does exercise intensity affect blood pressure and heart rate in obese adolescents? A 6-month multidisciplinary randomized intervention study.

BACKGROUND: Aerobic exercise improves cardiovascular health in general, but whether the impact varies with exercise intensity is not clear. OBJECTIVE: The aim of the current study was to compare the effects of a high-intensity aerobic exercise training (HIT) vs. a low-intensity aerobic exercise training (LIT) on blood pressure (BP), heart rate (HR) and heart rate variability (HRV) in obese adolescents. METHODS: Forty-three (13-18 years) Tanner stage (III-IV) matched obese adolescents were studied in a randomized trial of either HIT (corresponding to the ventilatory threshold I; n = 20) or LIT (corresponding to 20% below the ventilatory threshold I; n = 23) programme for a period of 6 months. All participants also received a multidisciplinary therapy that included nutritional, psychological and clinical counselling. Both HIT and LIT sessions were isocaloric, with energy expenditure set at 350 kcal. BP, HR and HRV were measured along with markers of body adiposity and insulin resistance before and after the respective interventions. RESULTS: The participants in both groups had similar physical and clinical characteristics. After the 6-month intervention, systolic, diastolic and mean BP decreased (P < 0.05, for all) similarly in both groups, whereas waist circumference, HR and HRV showed beneficial changes only in the HIT group (P < 0.05). CONCLUSION: Aerobic exercise training set at a high intensity compared with the low intensity appears to have additional benefits on abdominal obesity and cardiovascular health in that it enhances the parasympathetic and autonomic modulation of the heart in obese adolescents.

Effects of long-term periodized resistance training on body composition, leptin, resistin and muscle strength in elderly post-menopausal women.

AIM: Objective of the study was to determine the effects of a periodized resistance training program on body composition, plasmatic levels of leptin and resistin, and muscle strength in elderly post-menopausal women. METHODS: Twenty-three post-menopausal women (age= 63.02±4.42 years; height 1.55±0.06 m; body mass 67.56±2.26 kg) were submitted to 12 months of periodized resistance training twice a week. The training program consisted of 3 sets of 6-14 repetitions maximal (RM). Body composition (DXA), muscle strength (bench press, leg press 45º and arm curl), plasmatic levels of resistin and leptin (ELISA method) were assessed before and after the training program. Paired Student's t test was used for comparison between pre- and post-training values. RESULTS: There was a significant increase in muscle strength and lean body mass; decrease in body mass, body fat percentage and fat mass after 12 months of resistance training, a part from the decrease in leptin and resistin levels. CONCLUSION: Long-term periodized resistance training prevents aging sarcopenia, decreases body fat and systemic markers of inflammation in postmenopausal elderly women.

Relationship between nonalcoholic fatty liver disease prevalence and visceral fat in obese adolescents.

BACKGROUND: Visceral adiposity is the major risk factor for paediatric nonalcoholic fatty liver disease. AIMS: Determine the prevalence of nonalcoholic fatty liver disease according to the visceral fat quartile. SUBJECTS: 181 obese adolescents including 113 girls (16.58+/-1.56 years) and 68 boys (16.87+/-1.62 years) were evaluated. METHODS: The inclusion criteria were obesity and post-pubertal stage of Tanner. Visceral fat of obese adolescents was distributed in quartiles after ultrasound nonalcoholic fatty liver disease diagnosis. RESULTS: Nonalcoholic fatty liver disease prevalence was 45.30%. It was observed that 62.07% and 76.47% of girls and boys with nonalcoholic fatty liver disease were found in the 4th quartile. In a multivariate logistic analysis it was observed that only visceral fat remained statistically significant, every 1cm increase in visceral fat was associated with a 1.97 fold (95% CI 1.06-3.66) in boys and 2.08 fold (95% CI 1.38-3.13) in girls increased risk to develop nonalcoholic fatty liver disease. Indeed it was verified a positive correlation between visceral fat, body mass index, insulin levels, homeostasis model assessment insulin resistance index and steatosis degree. CONCLUSIONS: Our findings suggested that the expansion of visceral fat was a determinant factor to increase nonalcoholic fatty liver disease prevalence and the visceral fat measured by ultrasound might be a good predictor to identify risk for nonalcoholic fatty liver disease in obese adolescents. It was confirmed by a stronger correlation between visceral fat and body mass index.