Carbohydrate Intake and Gut Hormone Release During Exercise
Condition: Obesity
Study type: Interventional

Summary: 
      It is well known that following a single session of moderate-to-high intensity exercise
      individuals experience a temporary suppression of hunger and a delay in the commencement of
      eating. This effect is believed to be due to changes in blood concentrations of specific
      hormones released from the gut that influence appetite.

      Individuals undertaking physical activity often consume foods immediately before exercise in
      order to improve their performance. However, it is currently unknown whether this eating
      practice influences the gut hormone response to exercise as well as how hungry an individual
      feels post-exercise.

      Therefore, the aim of this study is to investigate the effect of consuming a sugary
      (carbohydrate) drink immediately before starting an exercise session on the concentration of
      these gut hormones as well as the amount of food eaten in the hours following exercise
      completion.
    

Detailed description: 
      It is well established that following an acute bout of moderate-to-high intensity exercise
      individuals experience a transient suppression of hunger and a delay in the commencement of
      eating - a phenomenon referred to as exercise-induced anorexia. Acute exercise modulates the
      concentrations of gut hormones known to influence satiety, including the anorexigenic
      hormones glucagon-like peptide 1 (GLP-1) and peptide tyrosine tyrosine (PYY), as well as the
      acylated form of the orexigenic hormone ghrelin. These alterations in gut hormone
      concentrations have consequently been hypothesised to play a key role in exercise-induced
      anorexia.

      Despite suppressing hunger and delaying eating, acute exercise does not appear to alter
      short-term energy intake in the immediate hours following exercise completion. The absence of
      a compensatory response therefore creates an energy deficit capable of inducing weight loss.
      Strategies that augment the gut hormone response to acute exercise may thus increase the
      potency of exercise as a weight-loss tool.

      Research investigating the effect of exercise on appetite has frequently utilised
      participants in a fasting state. Undertaking exercise in this physiological condition
      contradicts current practices, as athletes often consume a carbohydrate source immediately
      prior to exercise in an attempt to maximise performance. It is currently unknown as to
      whether the consumption of carbohydrate during this period may further enhance the gut
      hormone response to exercise, and thus research into a potential additive effect is
      warranted.

      High-intensity exercise increases sympathetic nervous system activity and catecholamine
      release. Catecholamine concentrations are negatively correlated with acylated ghrelin
      concentrations and may directly stimulate GLP-1 and PYY release via activation of β-receptors
      located on L-cells. The decrease in gastric emptying rate that is observed during
      high-intensity exercise is also attributed to this increase in sympathetic activity.
      Consequently, an increase in sympathetic nervous system activity has been postulated as a key
      mechanism underlying exercise-induced changes in gut hormone concentrations. However, to our
      knowledge, no study has directly measured the relationship between sympathetic nervous system
      activity and anorexigenic gut hormone release during exercise.

      Therefore, the aim of this study is to examine any potential additive effects of carbohydrate
      ingestion immediately prior to exercise on gut hormone release and post-exercise appetite
      suppression. Furthermore, this study will look to investigate the mechanisms underlying
      changes in gut hormone concentrations experienced during exercise.
    

Intervention name(s): Maltodextrin (carbohydrate); Exercise; Rest; Water
Intervention type(s): Dietary Supplement; Other; Other; Other
Intervention description(s): A drink containing 300ml of water and 75g of maltodextrin; 30 minutes on a cycle ergometer working at 75% VO2 max; 30 minutes laying on a bed; A drink containing 300ml of water
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: Participants perform all four trials in a randomized order
Masking: Double (Participant, Investigator)
Primary purpose: Basic Science
Keywords: carbohydrate; exercise; PYY; GLP-1; ghrelin; hormones