The Role of Heart Rate on the Associations Between Body Composition and Heart Rate Variability in Children With Overweight/Obesity: The ActiveBrains Project.

BACKGROUND: Heart rate variability (HRV) is negatively associated with body mass index and adiposity in several populations. However, less information is available about this association in children with overweight and obesity, especially severe/morbid obesity, taking into consideration the dependence of HRV on heart rate (HR). OBJECTIVES: (1) to examine associations between body composition measures and HRV, (2) to study differences in HRV between children with overweight and severe/morbid obesity; and (3) to test whether relationships and differences tested in objectives 1 and 2, respectively are explained by the dependency of HRV on HR. METHODS: A total of 107 children with overweight/obesity (58% boys, 10.03 ± 1.13 years) participated in this study. Body composition measures were evaluated by Dual-energy X-ray absorptiometry (DXA). HRV parameters were measured with Polar RS800CX®. RESULTS: Body composition measures were negatively associated with HRV indicators of parasympathetic activity (ß values ranging from -0.207 to -0.307, all p < 0.05). Children with severe/morbid obesity presented lower HRV values with respect to children with overweight/mild obesity in HRV parameters indicators of parasympathetic activity (p = 0.035). All associations disappeared after further adjustment for HR (all p > 0.05). CONCLUSION: All associations between adiposity/obesity and HRV could be explained by HR, suggesting a key confounding role of HR in HRV studies in children with weight disturbances.

An exercise-based randomized controlled trial on brain, cognition, physical health and mental health in overweight/obese children (ActiveBrains project): Rationale, design and methods.

The new and recent advances in neuroelectric and neuroimaging technologies provide a new era for further exploring and understanding how brain and cognition function can be stimulated by environmental factors, such as exercise, and particularly to study whether physical exercise influences brain development in early ages. The present study, namely the ActiveBrains project, aims to examine the effects of a physical exercise programme on brain and cognition, as well as on selected physical and mental health outcomes in overweight/obese children. A total of 100 participants aged 8 to 11 years are randomized into an exercise group (N=50) or a control group (N=50). The intervention lasts 20-weeks, with 3-5 sessions per week of 90 min each, and is mainly focused on high-intensity aerobic exercise yet also includes muscle-strengthening exercises. The extent to what the intervention effect remains 8-months after the exercise programme finishes is also studied in a subsample. Brain structure and function and cognitive performance are assessed using structural and functional magnetic resonance imaging and electroencephalographic recordings. Secondary outcomes include physical health outcomes (e.g. physical fitness, body fatness, bone mass and lipid-metabolic factors) and mental health outcomes (e.g. chronic stress indicators and overall behavioural and personality measurements such as anxiety or depression). This project will substantially contribute to the existing knowledge and will have an impact on societies, since early stimulation of brain development might have long lasting consequences on cognitive performance, academic achievement and in the prevention of behavioural problems and the promotion of psychological adjustment and mental health. Clinical trials. Gov identifier: NCT02295072.

Activating brown adipose tissue through exercise (ACTIBATE) in young adults: Rationale, design and methodology.

AIMS: The energy expenditure capacity of brown adipose tissue (BAT) makes it an attractive target as a therapy against obesity and type 2 diabetes. BAT activators namely catecholamines, natriuretic peptides and certain myokines, are secreted in response to exercise. ACTIBATE will determine the effect of exercise on BAT activity and mass measured by positron emission tomography/computed tomography (PET/CT, primary outcome) in young adults. ACTIBATE will also investigate the physiological consequences of activating BAT (secondary outcomes). METHODS: ACTIBATE will recruit 150 sedentary, healthy, young adults (50% women) aged 18-25 years. Eligible participants will be randomly assigned to a non-exercise group (n ≈ 50) or one of two exercise groups (n=50 each). Participants in the exercise groups will perform aerobic and strength training 3-4 days/week at a heart rate equivalent to 60% of heart rate reserve (HRres), and at 50% of 1 repetition maximum (RM) for the moderate-intensity group, and at 80% of HRres and 70% RM for the vigorous-intensity group. Laboratory measures completed at baseline and 6 months include BAT activity and mass, resting energy expenditure, meal and cold-induced thermogenesis, body temperature regulation and shivering threshold, body composition and cardiovascular disease risk factors. We will also obtain biopsies from abdominal subcutaneous white adipose tissue and skeletal muscle to analyse the expression of genes encoding proteins involved in the thermogenic machinery. DISCUSSION: Findings from ACTIBATE will have significant implications for our understanding of exercise and its protective effects against the development of type 2 diabetes, obesity and related metabolic diseases. ClinicalTrials.gov ID: NCT02365129.