Training in the Fasted State, Glucose Metabolism and Energy Balance

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.

Assessed via an Actiheart monitor, completed at baseline and during the last week of the intervention

Citrate Synthase Activity (mitochondrial citrate synthase activity in each muscle sample in an immunocapture based manner)

Change after 6 weeks. For each participant the protein content will be presented as the fold change from baseline (arbitrary units).

Change after 6 weeks. For each participant the protein content will be presented as the fold change from baseline (arbitrary units)

Change after 6 weeks. For each participant the protein content will be presented as the fold change from baseline (arbitrary units)

Change after 6 weeks. For each participant the protein content will be presented as the fold change from baseline (arbitrary units)

Change throughout complete training period (weeks 1 through to 6). Samples will be collected during every training session (three times weekly for six weeks)

Change throughout complete training period (weeks 1 through to 6). Samples will be collected during every training session (three times weekly for six weeks)

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.

Inclusion Criteria: Male Aged 18-49 Body mass index (BMI) > 25 kg/m2 Weight stable for > 6 months Not currently engaging in any form of structured exercise Be able and willing to give informed oral and written consent Complete and meet the defined criteria of pre-study questionnaires and screen Exclusion Criteria: Have a history of metabolic, cardio-pulmonary or musculoskeletal disease Have plans to change diet and/or physical activity outside of the intervention Taking regular medication or food supplements from which it is not possible to refrain and which are known to influence any of the outcome measures. Failure to refrain from alcohol and/or caffeine containing drinks or strenuous exercise one day before or during the trial days Smokers Any reported condition or behavior deemed to pose a risk to the participant or introduce bias into the experiment

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Van Proeyen K, Szlufcik K, Nielens H, Pelgrim K, Deldicque L, Hesselink M, Van Veldhoven PP, Hespel P. Training in the fasted state improves glucose tolerance during fat-rich diet. J Physiol. 2010 Nov 1;588(Pt 21):4289-302. doi: 10.1113/jphysiol.2010.196493.

Edinburgh RM, Bradley HE, Abdullah NF, Robinson SL, Chrzanowski-Smith OJ, Walhin JP, Joanisse S, Manolopoulos KN, Philp A, Hengist A, Chabowski A, Brodsky FM, Koumanov F, Betts JA, Thompson D, Wallis GA, Gonzalez JT. Lipid Metabolism Links Nutrient-Exercise Timing to Insulin Sensitivity in Men Classified as Overweight or Obese. J Clin Endocrinol Metab. 2020 Mar 1;105(3):660-76. doi: 10.1210/clinem/dgz104.