In healthy individuals, the body responds to glucose (sugar) ingestion by reducing the amount released from the liver. At the same time, skeletal muscles increase the rate at which they remove the glucose from the bloodstream, via the actions of the hormone insulin. This ensures that blood glucose levels remain in a controlled range. However, in developed countries, diseases such as metabolic syndrome and type 2 diabetes are becoming prevalent, due to dietary modifications and a reduction in physical activity. As one of the prominent barriers to regular physical activity is a lack of time, finding ways to maximize the health benefits of exercise is a priority for researchers. The investigators want to understand potential differences in the effects of six weeks of aerobic training, with the exercise performed either after breakfast or after a prolonged fast. Specifically, this research aims to investigate whether there is a difference in the change in processes implicated in glucose regulation and secondly, in subsequent eating and physical activity behaviors. By investigating these changes this work will explore how exercise and nutrition can be optimized to benefit health and weight loss.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
NONE
Enrollment
30
Moderate intensity exercise
Breakfast consumption
Normal physical activity and dietary behaviors maintained
Department for Health, University of Bath
Bath, United Kingdom
Postprandial plasma glucose concentrations
Response to oral glucose tolerance test (area under the curve)
Time frame: 120 mins - (change after 6 weeks)
Postprandial insulin concentrations
Response to oral glucose tolerance test (area under the curve)
Time frame: 120 mins - (change after 6 weeks)
Oral Glucose Insulin Sensitivity Index
Response to oral glucose tolerance test
Time frame: 120 mins - (change after 6 weeks)
Cardiorespiratory fitness (VO2max)
Time frame: Change after 6 weeks
Habitual energy intake
Assessed via a food diary, completed at baseline and during the last week of the intervention
Time frame: Change after 6 weeks
Habitual energy expenditure
Assessed via an Actiheart monitor, completed at baseline and during the last week of the intervention
Time frame: Change after 6 weeks
Body mass (kg)
Time frame: Change after 6 weeks
Waist and hip circumference (cm)
Time frame: Change after 6 weeks
Maximal rate of whole-body lipid oxidation (g/min)
During an incremental exercise test
Time frame: Change after 6 weeks
Fasting plasma glucose concentration
Fasting plasma glucose concentration (mmol/L)
Time frame: Basal Concentrations - (change after 6 weeks)
Fasting plasma insulin concentration
Fasting plasma insulin concentration (pmol/L)
Time frame: Basal Concentrations - (change after 6 weeks)
Postprandial non-esterified fatty acid concentrations
Response to oral glucose tolerance test (total and incremental area under the curve)
Time frame: 120 mins - (change after 6 weeks)
Fasting plasma triglyceride concentrations
Fasting plasma triglyceride concentrations (mmol/L)
Time frame: Basal Concentrations - (change after 6 weeks)
Fasting plasma total cholesterol concentrations
Fasting plasma total cholesterol concentrations (mmol/L)
Time frame: Basal Concentrations - (change after 6 weeks)
Fasting plasma HDL cholesterol concentrations
Fasting plasma HDL cholesterol concentrations (mmol/L)
Time frame: Basal Concentrations - (change after 6 weeks)
Fasting plasma LDL cholesterol concentrations
Fasting plasma LDL cholesterol concentrations (mmol/L)
Time frame: Basal Concentrations - (change after 6 weeks)
Fasting plasma non-esterified fatty acid concentrations
Fasting plasma non-esterified fatty acid concentrations (mmol/L)
Time frame: Basal Concentrations - (change after 6 weeks)
Waist to hip ratio
Waist circumference (cm) divided by hip circumference (cm)
Time frame: Change after 6 weeks
Citrate Synthase Activity (mitochondrial citrate synthase activity in each muscle sample in an immunocapture based manner)
Skeletal muscle (vastus lateralis). Citrate Synthase Activity Assay Kit.
Time frame: Change after 6 weeks
Protein content of mitochondrial respiratory chain proteins
Skeletal muscle (vastus lateralis). Complex I, Complex II, Complex III, Complex IV.
Time frame: Change after 6 weeks. For each participant the protein content will be presented as the fold change from baseline (arbitrary units).
Protein content of carnitine palmitoyltransferase I (CPT-1)
Skeletal muscle (vastus lateralis)
Time frame: Change after 6 weeks. For each participant the protein content will be presented as the fold change from baseline (arbitrary units)
Protein content of cluster of differentiation 36 (CD36)
Skeletal muscle (vastus lateralis)
Time frame: Change after 6 weeks. For each participant the protein content will be presented as the fold change from baseline (arbitrary units)
Protein content (total and phosphorylated form) of AMP-activated protein kinase (AMPK)
Skeletal muscle (vastus lateralis)
Time frame: Change after 6 weeks. For each participant the protein content will be presented as the fold change from baseline (arbitrary units)
Resting metabolic rate (RMR)
Assessed via indirect calirometry
Time frame: Change after 6 weeks
Energy balance
Total energy expenditure minus total energy intake
Time frame: Change after 6 weeks (during week 6 of intervention versus baseline monitoring)
Whole-body lipid utilisation during exercise
Assessed via indirect calirometry during every exercise session (at ten minute intervals)
Time frame: Change throughout complete training period (weeks 1 through to 6). Samples will be collected during every training session (three times weekly for six weeks)
Whole-body carbohydrate utilisation during exercise
Assessed via indirect calirometry during every exercise session (at ten minute intervals)
Time frame: Change throughout complete training period (weeks 1 through to 6). Samples will be collected during every training session (three times weekly for six weeks)
Homeostasis Model Assessment (HOMA2-IR)
The Homeostasis Model Assessment (HOMA) estimate of steady state beta cell function (%B) and insulin sensitivity (%S). Derived from fasting plasma glucose and fasting plasma insulin concentrations.
Time frame: Change after 6 weeks
Fasting plasma glycerol concentrations
Fasting plasma glycerol concentrations (mmol/L)
Time frame: Basal Concentrations - (change after 6 weeks)
Postprandial plasma glycerol concentrations
Response to oral glucose tolerance test (total and incremental area under the curve)
Time frame: Change after 6 weeks
Adipose Tissue Insulin Resistance Index (Adipo-IR)
Response to oral glucose tolerance test (total and incremental area under the curve)
Time frame: Change after 6 weeks
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