The Influence of Energy Expenditure, Sex and Eating Behaviours on Energy Intake and Appetite in Young Adolescents

Current physical activity recommendations are being met by less than 21 % of children between 5-15 y. Recent Government initiatives are aiming to increase children’s participation in exercise. However, the effects on an imposed bout of exercise-induced energy expenditure (EE) on energy intake (EI) and appetite (hunger, fullness and prospective consumption) in normal weight children have received a limited research focus to date. Therefore, this thesis aimed to investigate how an imposed bout of exercise-induced energy expenditure (EE) on energy intake (EI) and appetite in normal weight children The first study investigated whether 17 habitually active girls were able to accurately increase their EI to match the EE following 60 min moderate intensity walking exercise. On average 17% of the EE was compensated for by an increase in EI. However, the ranged for EI change was -160% to +166% indicating large individual responses. The second study investigated whether 30 min of maximal sprint intermittent sprint cycling exercise would significantly alter EI or appetite in 13 boys and 13 girls. In the boys, hunger and prospective consumption were suppressed whilst fullness increased immediately following the exercise, whilst EI was significantly increased in response to the exercise condition. No significant changes to appetite or EI were observed in the girls. The third study investigated whether a mid-morning snack, moderate intensity cycling exercise (energy matched to snack) or both would alter EI or appetite in 20 boys and 18 girls. Irrespective of sex, hunger and prospective consumption were suppressed whilst fullness increased following the mid-morning snack, however this change in appetite did not alter EI as no significant differences were found between conditions. The fourth study investigated whether 99 recreational sports players (males/females, adults/children) were able to conceptualise their EE following 1 h habitual training into quantifiable amounts of food (chocolate) or drink (sports drink). Only 36 % of the EE from the exercise was met by the estimated amounts of food or drink. Age, sex nor sports participation significantly altered the participants’ accuracy of estimation. The fifth study investigated whether sex or dietary restraint impacted brain activation responses to visual food stimuli in 15 boys and 14 girls between a fed and fasted condition. Significant differences in brain activation were found between conditions, sexes and dietary restraint, potentially suggesting the differences observed in the previous experimental studies could be attributed to neurological alterations between participants. In conclusion, the findings presented demonstrate the changes in EI between young adolescents in response to an imposed bout of exercise are extremely variable. Whilst eating behaviours failed to correspond to the EI differences observed between participants, potentially brain activation differences may be responsible. The sex of the participant is more likely to impact EI and appetite following maximal sprint intensity exercise, more so than a bout of moderate intensity exercise. Future research should focus on determining what underpins the variable change in EI between participants following a bout of exercise.Kelloggs Lt