Observational reports showing infrequent breakfast consumption to be associated with increased adiposity and cardiometabolic disease risk in children and adolescents have fuelled concerns over the low prevalence of habitual breakfast consumption among adolescents. Yet, only experimental study designs can determine the causal effects of breakfast consumption on health-related variables and such research has typically targeted adults. Adolescent girls may respond differently to manipulations in breakfast consumption than adults because they have distinct hormonal, metabolic and behavioural profiles. Further, a link between breakfast and physical activity in adolescent girls has particular public health relevance because the adolescent decline in both breakfast consumption frequency and physical activity is more pronounced in girls than in boys. Thus, the primary aim of the current study is to use a randomised, cross-over design to compare the effect of seven consecutive days of breakfast omission with standardised breakfast consumption on free-living PAEE in adolescent girls. The secondary aims are to examine the effects on energy intake, perceived appetite and energy levels.~Using a randomized crossover design, girls aged 11-14 years will complete two, 7-day conditions. A standardized breakfast will consumed every day before 09:00 in the daily breakfast consumption condition. No energy-providing nutrients will consumed (i.e., only water) before 10:30 in the breakfast omission condition. Combined heart rate-accelerometry will be used to estimate physical activity energy expenditure and digital photography complemented with written food diaries will be used to assess energy intake during each condition; these data will be separated into three time segments: wake to 10:30, 10:30 to 15:30 and 15:30 to bed. Visual analogue scales will be used to assess perceptions of hunger, fullness, tiredness and energy levels on waking and at 09:00 and 10:30. Statistical analyses will be completed using condition by time of day linear mixed models.
There is a distinct lack of experimental evidence on whether breakfast consumption and omission affect energy balance-related variables. This research is of particular relevance to adolescent girls due to concerns of low rates of breakfast consumption and physical activity in this population. This study aims to compare the effect of seven consecutive days of breakfast omission with standardised breakfast consumption on free-living physical activity energy expenditure, energy intake and perceived appetite and energy levels in adolescent girls.