Effect of manipulations in exercise and breakfast on metabolism in overweight and non-overweight children and adolescents

Obesity and insulin resistance are serious health concerns in children and adolescents (young people). Interventions to increase the potential for fat oxidation and improve insulin sensitivity could have widespread clinical relevance. Although exercise is often advocated for health, the factors implicated in the relationship between exercise, fat oxidation and insulin resistance are not well understood in young people. This thesis has investigated the effect of manipulations in exercise and breakfast on metabolism in young people, focusing on fat oxidation and postprandial blood glucose control. The first experimental study, Chapter 4, compared two different exercise protocols for estimating the intensity corresponding to maximal fat oxidation (Fatmax) in non-overweight prepubertal children. A 3 min incremental protocol was recommended to provide an estimation of Fatmax using a wide range of intensities in this population. Using this protocol, Chapter 5 demonstrated that Fatmax was higher for treadmill compared with cycling exercise in pre- to early pubertal children. Furthermore, treadmill exercise resulted in higher rates of fat oxidation over a range of absolute and relative intensities and fat oxidation remained high over a wider range of intensities. Therefore, treadmill exercise (walking or slow running) is clearly preferential for promoting fat oxidation in this population. Subsequently, Chapter 6 examined the effect of mixed breakfast meals containing high (HGI) and low (LGI) glycaemic index carbohydrates on blood glucose, plasma insulin and fat oxidation in overweight and non-overweight girls. Breakfast GI did not affect fat oxidation during the postprandial rest period or subsequent exercise. However, the main finding of this study related to blood glucose; the higher blood glucose response following the HGI compared with LGI breakfast was more pronounced in the overweight girls. This suggested a reduced ability to cope with the metabolic demands of HGI breakfast consumption in overweight girls and highlighted that strategies to reduce insulin resistance in this population are required. Consequently, Chapter 7 investigated the effect of treadmill exercise at Fatmax performed 16 h prior to HGI breakfast consumption on blood glucose, plasma insulin and fat oxidation in overweight and non-overweight girls. Fatmax exercise reduced the postprandial insulin response in the non-overweight, but not the overweight, girls while blood glucose was unchanged in both groups. More encouragingly, fat oxidation was increased after exercise in both the overweight and non-overweight girls. Collectively, the four experimental studies within this thesis have demonstrated that treadmill exercise at Fatmax is an effective means of elevating fat oxidation both during and up to 16 h after exercise. When considering postprandial glucose and insulin responses to HGI breakfast consumption, LGI breakfasts should be recommended for overweight girls, whilst acute treadmill exercise at Fatmax can reduce postprandial insulin concentrations in non-overweight girls. Walking or slow running (Fatmax treadmill exercise) and LGI breakfast consumption may be best advocated in combination for promoting fat oxidation and improving postprandial blood glucose control in young people. These two simple lifestyle-related strategies may provide an effective, safe and attractive means for preventing and treating obesity, insulin resistance and related disorders. Key words: exercise, metabolism, substrate oxidation, fat oxidation, glucose, insulin, glycaemic index, overweight, children, adolescents

Bose-Hubbard model with random impurities: Multiband and nonlinear hopping effects

We investigate the phase diagrams of theoretical models describing bosonic atoms in a lattice in the presence of randomly localized impurities. By including multiband and nonlinear hopping effects we enrich the standard model containing only the chemical-potential disorder with the site-dependent hopping term. We compare the extension of the MI and the BG phase in both models using a combination of the local mean-field method and a Hartree-Fock-like procedure, as well as, the Gutzwiller-ansatz approach. We show analytical argument for the presence of triple points in the phase diagram of the model with chemical-potential disorder. These triple points however, cease to exists after the addition of the hopping disorder.Comment: version accepted in Phys. Rev.

Effect of breakfast omission and consumption on energy intake and physical activity in adolescent girls: a randomised controlled trial

It is not known if breakfast consumption is an effective intervention for altering daily energy balance in adolescents when compared with breakfast omission. This study examined the acute effect of breakfast consumption and omission on free-living energy intake (EI) and physical activity (PA) in adolescent girls. Using an acute randomised crossover design, forty girls (age 13.3 ± 0.8 y, body mass index 21.5 ± 5.0 kg∙m-2) completed two, 3-day conditions in a randomised, counter-balanced order: no breakfast (NB) and standardised (~1962 kJ) breakfast (SB). Dietary intakes were assessed using food diaries combined with digital photographic records and PA was measured via accelerometry throughout each condition. Statistical analyses were completed using repeated measures analysis of variance. Post-breakfast EI was 483 ± 1309 kJ/d higher in NB vs. SB (P=0.025), but total daily EI was 1479 ± 1311 kJ/d higher in SB vs. NB (P<0.0005). Daily carbohydrate, fibre and protein intakes were higher in SB vs. NB (P<0.0005), whereas daily fat intake was not different (P=0.405). Effect sizes met the minimum important difference of ≥0.20 for all significant effects. Breakfast manipulation did not affect post-breakfast macronutrient intakes (P≥0.451) or time spent sedentary or in PA (P≥0.657). In this sample of adolescent girls, breakfast omission increased post-breakfast free-living EI, but total daily EI was greater when a standardised breakfast was consumed. We found no evidence that breakfast consumption induces compensatory changes in PA. Further experimental research is required to determine the effects of extended periods of breakfast manipulation in young people

Effects of breaking up prolonged sitting following low and high glycaemic index breakfast consumption on glucose and insulin concentrations

Purpose: Breaking up prolonged sitting can attenuate the postprandial rise in glucose and insulin. Whether such effects are dependent of the glycaemic index (GI) of the consumed carbohydrate is unknown. This study examined the acute effects of breaking up prolonged sitting following a low GI and a high GI breakfast on postprandial glucose and insulin concentrations. Procedures: Fourteen adult males aged 22.1 ± 1.2 years completed four, 4 h experimental conditions: high GI breakfast followed by uninterrupted sitting (HGI-SIT), low GI breakfast followed by uninterrupted sitting (LGI-SIT), high GI breakfast followed by 2 min activity breaks every 20 min (HGI-ACT), and low GI breakfast followed by 2 min activity breaks every 20 min (LGI-ACT). Positive incremental area under the curve (iAUC) for glucose and insulin (mean [95% CI]) for each 4h experimental condition was calculated. Statistical analyses were completed using linear mixed models. Results: The sitting × breakfast GI interaction was not significant for glucose positive iAUC (P=0.119). Glucose positive iAUC (mmol/L4 h−1) was significantly lower in the activity breaks conditions than the uninterrupted sitting conditions (2.07 [2.24, 2.89] vs. 2.56 [1.74, 2.40], respectively, P=0.004) and significantly lower in the low GI conditions than the high GI conditions (2.13 [1.80, 2.45] vs. 2.51 [2.18, 2.84], respectively, P=0.022). Insulin concentrations did not differ between conditions (P ≥ 0.203). Conclusions: Breaking up prolonged sitting and lowering breakfast GI independently reduced postprandial glucose responses. This indicates that interrupting prolonged sitting and reducing dietary GI are beneficial approaches for reducing cardiometabolic disease risk

Carbohydrate needs of the young athlete

Carbohydrate (CHO) typically provides the majority of energy in the athlete’s diet and is essential to fuel high intensity exercise. Ensuring adequate energy is available to meet the demands of high energy expenditures is important in the young athlete to ensure proper growth, development, and maturation. Physiological and metabolic changes that accompany the transition from childhood to adolescence and to adulthood, combined with the additional energy expenditure arising from exercise, mean that the dietary needs of young athletes require special consideration. However, in contrast to the well-documented literature in adults, little research attention has been given to child and adolescent populations. Thus, the development of specific recommendations for CHO intake in young athletes is difficult. Nevertheless, it is possible to make some general recommendations. Both the total daily CHO intake and the timing of CHO consumption in relation to exercise can determine whether adequate CHO substrate is available for muscles and the central nervous system or whether CHO fuel sources might limit exercise performance. In terms of the overall diet, CHO should contribute to the majority of energy intake, which must be high enough to support growth and maturation whilst fuelling the additional physical activity, and consequently elevated energy expenditure, in young athletes. In particular, CHO is an important fuel for high intensity exercise in young athletes. Decrements in exercise performance, fatigue and changes in body composition may serve as useful indicators that CHO intake may not be adequate, particularly in female adolescent athletes. During exercise, drinks containing CHO could be considered for young athletes engaged in endurance exercise due to the preferential use of exogenous CHO in younger athletes in the pre- or early- pubertal stages. However, evidence on CHO loading and CHO for post-exercise recovery does not appear to be available in children or adolescents. This chapter provides an overview of the available evidence that can be used to inform recommendations for CHO intake and timing in young athletes. Where no direct evidence in young athletes is available, we have relied on the relevant adult-based literature whilst emphasising that the direct translation and application of these findings to children and adolescents must be viewed cautiously

Metabolism and exercise during youth — The year that was 2017

Two publications were selected because they are excellent representations of studies examining different ends of the exercise-sedentary behavior continuum in young people. The first study is an acute response study with 13 mixed-sex, mid to late adolescents presenting complete data from 4 different randomized experimental crossover conditions for analyses. Continuous glucose monitoring showed that interrupting prolonged continuous sitting with body-weight resistance exercises reduced the postprandial glucose concentration compared with a time-matched uninterrupted period of sitting. Furthermore, the effects of the breaks in sitting time were independent of the energy content of the standardized meals, but variations in the area under the glucose time curves expression were important. The second study adopted a chronic 12-week exercise training intervention design with a large sample of obese children and adolescents who were allocated randomly to high-intensity interval training (HIIT), moderate-intensity continuous training, or nutritional advice groups. HIIT was the most efficacious for improving cardiorespiratory fitness compared with the other interventions; however, cardiometabolic biomarkers and visceral/subcutaneous adipose tissue did not change meaningfully in any group over the 12 weeks. Attrition rates from both HIIT and moderate-intensity continuous training groups reduce the validity of the exercise training comparison, yet this still provides a solid platform for future research comparisons using HIIT in young people

Can physical activity support grief outcomes in individuals who have been bereaved? A systematic review

© The Author(s) 2021. This article is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.Background: In 2018, there were 616,014 registered deaths in the United Kingdom (UK). Grief is a natural consequence. Many mental health concerns, which can be identified as grief outcomes (e.g. anxiety and depression) in those who have experienced a bereavement, can be improved through physical activity. The objective of this review was to identify from the existing literature if physical activity can benefit grief outcomes in individuals who have been bereaved. Methods: A systematic review of nine databases was performed. Included studies (qualitative and quantitative) explored physical activity to help individuals (of any age) who had experienced a human bereavement (excluding national loss). Results: From 1299 studies screened, 25 met the inclusion criteria, detailing eight types of bereavement (parental (n = 5), spousal (n = 6), patient (n = 4), pre-natal (n = 3), later life (n = 1), caregiver (n = 1), multiple (n = 4) and non-defined (n = 1). Activities including yoga, running, walking and martial arts were noted as beneficial. Physical activity allowed a sense of freedom, to express emotions, provided a distraction and an escape from grief, whilst enhancing social support. Conclusion: There is some evidence that physical activity may provide benefit for the physical health and psychological wellbeing of those who have been bereaved, including when the loss has happened at a young age. This review is timely, given the wide-scale national loss of life due to COVID-19 and extends knowledge in this area. More research is needed to explore the benefits of physical activity for those who have been bereaved. In particular, there is a need for well-designed interventions which are tailored to specific activities, populations and grief outcomes.Peer reviewe

Beneficial postprandial lipaemic effects of interrupting sedentary time with high-intensity physical activity versus a continuous moderate-intensity physical activity bout: a randomised crossover trial

Objectives To compare the postprandial cardiometabolic response to prolonged sitting, continuous moderate-intensity physical activity (PA) followed by prolonged sitting, and interrupting prolonged sitting with hourly high-intensity PA breaks. Design Three-condition randomised crossover trial. Methods Fourteen sedentary and inactive adults aged 29 ± 9 years took part in three, 8-h conditions: (1) prolonged sitting (SIT), (2) a continuous 30-min moderate-intensity PA bout followed by prolonged sitting (CONT-SIT), and (3) sitting interrupted hourly with 2 min 32 s high-intensity PA bouts (SIT-ACT). The treadmill PA in conditions 2 and 3 were matched for energy expenditure. Two standardised test meals were consumed during each condition. Incremental area under the curve (iAUC) for each 8-h condition was calculated for glucose, insulin, triglyceride, and high-density lipoprotein cholesterol (HDL-C) concentrations. Statistical analyses were completed using linear mixed models. Results Compared with SIT, SIT-ACT lowered triglyceride iAUC by 2.23 mmol/L ∙ 8 h (95% CI −4.33, −0.13) and raised HDL-C iAUC by 0.99 mmol/L ∙ 8 h (0.05, 1.93) (all p ≤ 0.038). There was no significant difference in triglyceride or HDL-C iAUC between CONT-SIT and SIT or SIT-ACT (p ≥ 0.211). There were no significant differences between conditions for glucose or insulin iAUC (p ≥ 0.504). Conclusions This study suggests that interrupting prolonged sitting with hourly high-intensity PA breaks acutely improves postprandial triglyceride and HDL-C concentrations compared with prolonged sitting, whereas a continuous moderate-intensity PA bout does not

What roles does physical activity play following the death of a parent as a young person? A qualitative investigation

© The Author(s) 2023. This article is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.Background: Physical activity benefits physical and mental health. However, limited research investigates if physical activity can improve outcomes from the grieving process following the death of a parent. Methods: Semi-structured interviews were conducted with 14 individuals (n = 8 female; age M = 31.2 years), who had experienced the death of a parent when they were aged between 10 and 24 years old, using retrospective recall. Data were analysed inductively using thematic analysis. Results: Six themes were identified. Physical activity was seen as; 1) ‘Therapeutic’; providing an 2) ‘Emotional Outlet’ and created a strong sense of 3) ‘Social Support’. Alongside it 4) ‘Builds Confidence’, and led to 5) ‘Finding Yourself’ and 6) ‘Improved Health and wellbeing’ (physical and psychological). Conclusion: Physical activity has the potential to provide positive experiences following a parental bereavement. It can provide a sense of freedom and was seen to alleviate grief outcomes, build resilience, enable social support and create a stronger sense of self. Bereavement support services for young people who have experienced death of a parent should consider physical activity as a viable intervention to support the grieving process.Peer reviewe

Does parental support moderate the effect of children’s motivation and self-efficacy on physical activity and sedentary behaviour?

Objectives: 1) To test whether parental support moderates the direct effects of children's motivation and self-efficacy on objectively measured moderate-vigorous physical activity (MVPA) and sedentary time. 2) To explore differences in the relationships between boys and girls. Design: Cross-sectional observational study. Method: Data were collected from 430 9-11 year old UK children and their parents; parents selfreported on the support they provided to their children to be active (through providing transport, encouragement, watching, or taking part with their child), and children self-reported their motivation and self-efficacy towards exercise. MVPA and sedentary time were measured using accelerometers. Results: Both parent- and child-level factors were largely positively associated with children's MVPA and negatively related to sedentary time. There was no evidence of a moderation effect of parental support on MVPA or sedentary time in boys. Parental provision of transport moderated the effect of girls' motivation on week-day MVPA; more motivated girls were less active when transport was provided. Transport and exercising with one's child moderated the effect of motivation and self-efficacy on girls' sedentary time at weekends; more motivated girls, and those with higher self-efficacy were less sedentary when parents provided more frequent transportation or took part in physical activity with them. Conclusions: The results largely supported a model of the independent effects of parent and child determinants for moderate-to-vigorous physical activity, but there was evidence that some types of parent support can moderate sedentary time in girls. Further research is needed to explore the causal pathways between the observed cross-sectional results