Breakfast consumption (BC) is frequently associated with a healthy lifestyle, healthy body weight and favourable cardiometabolic health. Research from studies in adults suggests that breakfast skipping causes elevated plasma glucose and insulin concentrations after lunch. However, there is currently no evidence to suggest a similar metabolic response in adolescent girls, a population that frequently skips breakfast. The primary purpose of this study is to examine the effects of BC versus breakfast omission (BO) on metabolic responses after lunch in healthy adolescent girls.
Breakfast consumption (BC) is habitually associated with a healthy lifestyle (e.g., diet and physical activity), reduced adiposity and favourable cardiometabolic health profiles in children, adolescents and adults. Experimental research in adults has shown that breakfast consumption reduces the glycaemic and insulinemic response to lunch when compared with breakfast omission; this has been termed 'the second meal effect'. Further, breakfast consumption may improve exercise performance and increase free-living physical activity energy expenditure in adults. Understanding the postprandial metabolic responses to BC and breakfast omission (BO) in adolescent girls is particularly important, as this population frequently skips breakfast and have low physical activity levels. Yet, adolescent girls may respond differently to adults due to their distinct metabolic profiles, and past research has not targeted this population. The primary aim of this research is to examine whether BC versus BO affects postprandial glycaemic and insulinemic responses to lunch in adolescent girls. Secondly, it aims to examine the lipaemic and substrate oxidation responses during rest, substrate oxidation during an exercise bout performed later in the day, and physical activity enjoyment during the exercise bout.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
NONE
Enrollment
Consumption of breakfast: The breakfast provided was designed based on the "characteristics of an ideal breakfast" outlined in Giovannini et al., (2008). The breakfast provided in the present study will include the following: all-bran cereals (Kellogg's), semi-skimmed milk (Tesco), Royal Gala Apple (Tesco) and Orange Juice from Concentrate (Tesco) containing the amount of carbohydrates usually consumed at breakfast in the UK (Reeves et al., 2013). The portion for each participant will contain 0.06 g of carbohydrate per kcal of measured RMR. As the portion size (20% of daily calorie intake) will be calculated based on individual RMR , no leftovers will be allowed.
Omission of breakfast. Participants will consume water within 15 min, the individual volume of which will be calculated based on the liquid content of the breakfast \[milk (ml)+ orange juice (ml)\].
University of Bedfordshire
Bedford, Bedfordshire, United Kingdom
Post-lunch area under the curve (AUC) for glucose.
Net incremental AUC and total AUC for 2-hour period post lunch in each condition will be calculated for plasma glucose. Five finger prick blood samples will be taken at 15, 30, 60, 90 and 120 minutes post lunch.
Time frame: 2 hours
Total trial area under the curve (AUC) for glucose.
Net incremental AUC and total AUC for the 5-hour entire trial period in each condition will be calculated for plasma glucose. Finger prick blood samples will be taken at at 0 (baseline), 30, 60, 120 and 180 min after breakfast consumption or omission and at 15, 30, 60, 90 and 120 minutes after lunch consumption.
Time frame: 5 hours
Post-lunch area under the curve (AUC) for insulin.
Net incremental AUC and totral AUC for 2-hour period post lunch in each condition will be calculated for plasma insulin. Five finger prick blood samples will be taken at 15, 30, 60, 90 and 120 minutes post lunch.
Time frame: 2 hours
Total trial area under the curve (AUC) for insulin.
Net incremental AUC and total AUC for the 5-hour entire trial period in each condition will be calculated for plasma insulin. Finger prick blood samples will be taken at at 0 (baseline), 30, 60, 120 and 180 min after breakfast consumption or omission and at 15, 30, 60, 90 and 120 minutes after lunch consumption.
Time frame: 5 hours
Post-lunch resting substrate oxidation
Substrate oxidation (fat and carbohydrate) rates will be estimated using indirect calorimetry from expired air samples at four time points following lunch (30, 60, 90 and 120 minutes).
Time frame: 2 hours
Total trial resting substrate oxidation.
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Substrate oxidation (fat and carbohydrate) rates will be estimated using indirect calorimetry from expired air samples at baseline and at 4 time points after breakfast (30, 60, 120 and 180 minutes) and 4 time points following lunch (30, 60, 90 and 120 minutes).
Time frame: 5 hours
Maximum fat oxidation rate during exercise
An incremental 7-stage cycling test will be performed 2 hours after lunch for the determination of maximum fat oxidation. Each stage will last 4 minutes in duration, where participants will keep a steady pedalling rate of 60 revolutions per minute. The intensity for each stage was calculated based on the percentage (0%, 20%, 30%, 40%, 50%, 60%, 70%) of the theoretical maximal aerobic power. Fat oxidation rates will be estimated during the final minute of each stage using indirect calorimetry.
Time frame: During exercise (approximately 30 minutes)
Fatmax during exercise
An incremental 7-stage cycling test will be performed 2 hours after lunch for the determination of maximum fat oxidation. Each stage will last 4 minutes in duration, where participants will keep a steady pedalling rate of 60 revolutions per minute. The intensity for each stage was calculated based on the percentage (0%, 20%, 30%, 40%, 50%, 60%, 70%) of the theoretical maximal aerobic power. Fat oxidation rates will be estimated during the final minute of each stage using indirect calorimetry. The intensity at which maximum fat oxidation occurs will be defined as Fatmax.
Time frame: During exercise (approximately 30 minutes)
Physical activity enjoyment
Physical activity enjoyment measured using Physical Activity Enjoyment Scale (PACES) during the Fatmax incremental exercise test. The scale is composed of 16 statements (9 positive and 7 negative) which begin with the phrase "When I am physically active…". The participants must answer by giving an answer from 1 "disagree a lot" to 5 "agree a lot" to each statement. The average score of the positive statements is calculated to be used in the analysis.
Time frame: Following exercise (approximately 5-10 minutes post)
Post-lunch area under the curve (AUC) for triaclyglycerol
Net incremental AUC and total AUC for the 2-hour period post lunch in each condition will be calculated for plasma triaclyglycerol. Five finger prick blood samples will be taken at 15, 30, 60, 90 and 120 minutes post lunch.
Time frame: 2 hour
Total trial area under the curve (AUC) for triaclyglycerol
Net incremental AUC and total AUC for the 5-hour entire trial period in each condition will be calculated for plasma triacylglycerol. Finger prick blood samples will be taken at at 0 (baseline), 30, 60, 120 and 180 min after breakfast consumption or omission and at 15, 30, 60, 90 and 120 minutes after lunch consumption.
Time frame: 5 hours