Effects of Pre-exercise Carbohydrate Restriction Relative to Fasting on Metabolism, Appetite, and Energy Intake in Healthy Males.
Condition: Obesity; Metabolic Syndrome
MeSH terms: Metabolic Syndrome
Study type: Interventional

Summary: 
      This study will compare the metabolic, appetite, energy intake, and perceptual responses to a
      bout of exercise completed in the evening after after a low-carbohydrate lunch meal (<10%
      carbohydrate content / 0.2 g/kg carbohydrate; LO-CHO), with the responses to exercise
      performed after a lunch meal containing a high carbohydrate content (~60% carbohydrate
      content / 2.2 g/kg carbohydrate; HI-CHO), and after skipping lunch and fasting for 8 hours
      since breakfast (FAST).
    

Detailed description: 
      Regular exercise is known to be a successful strategy for improving several facets of health
      and maintaining body weight. However, many people are not engaging in enough exercise, and
      some may not be achieving maximum benefits from the exercise that they already do. Performing
      exercise in the overnight fasted state has been shown to reduce energy intake over the course
      of a single day, without any compensatory reductions in free-living energy expenditure.
      Despite these promising findings, it is likely that not every member of the population is
      logistically able to perform exercise in the morning due to various work, family and social
      commitments, and exercise in the evening may be a logical alternative for these individuals.

      Studies have found that exercise performed after an overnight fast may incur superior
      improvements in insulin sensitivity in lean individuals (Van Proeyen et al., 2010), and
      individuals with overweight or obesity (Edinburgh et al., 2020), compared to exercising after
      breakfast. These superior improvements may be mediated, in part, by an increased mobilisation
      and oxidation of endogenous lipid stores. Additionally, overnight fasted exercise may result
      in a more negative energy balance than exercising after breakfast (Bachman et al., 2016;
      Edinburgh et al., 2019). We recently examined whether exercise performed in the evening
      following an extended period of fasting (7 h) would induce similar responses to overnight
      fasted exercise regarding substrate oxidation patterns and subsequent energy intake
      (manuscript in preparation - NCT04742530). This research question was important, as we
      speculate that a large proportion of the population are likely unable to perform exercise in
      the morning after an overnight fast due to various logistical barriers. Therefore fasting
      prior to evening exercise could act as an alternative for these individuals.

      We found that compared to consuming a carbohydrate-containing meal 2 h prior, fasting before
      evening exercise resulted in elevated fat oxidation rates during exercise, but was
      accompanied by compensatory eating at dinner. Additionally, participants reported that
      fasting throughout the afternoon was difficult. The long-term efficacy of fasted evening
      exercise may, therefore, be limited by increased hunger and compensatory energy intake.

      Consuming a meal lower in carbohydrate and higher in protein and/or fat can increase rates of
      fat oxidation during exercise (Rowlands & Hopkins, 2002; Oliviera et al., 2021). Protein is
      also the most satiating macronutrient, and high-protein diets are associated with reductions
      in energy intake. Consuming a high-protein pre-exercise meal compared to a typical
      high-carbohydrate meal also led to greater exercise-induced elevations in hormones typically
      associated with increased satiety and reduced hunger: peptide tyrosine-tyrosine (PYY) and
      glucagon-like peptide-1 (GLP-1) (Oliviera et al., 2021). Therefore, consuming a meal with a
      low carbohydrate content and higher protein content before exercise, rather than completely
      fasting, could be utilised to enhance the metabolic responses to exercise, whilst
      simultaneously managing appetite and subsequent energy intake. Further research is needed to
      fully understand the metabolic and appetite-related effects of a low-carbohydrate,
      higher-protein meal prior to exercise in the evening, compared to a typically consumed
      higher-carbohydrate meal and complete fasting.
    

Intervention name(s): Low-Carbohydrate Pre-Exercise Meal; High-Carbohydrate Pre-Exercise Meal; Fasted Exercise
Intervention type(s): Behavioral; Behavioral; Behavioral
Intervention description(s): Sixty minutes of cycling at 60% VO2peak will take place on a stationary bicycle ergometer at 16:00, after having consumed a low-carbohydrate lunch meal (<10% carbohydrate; 35% estimated energy requirements) 2.5 hours prior.; Sixty minutes of cycling at 60% VO2peak will take place on a stationary bicycle ergometer at 16:00, after having consumed a high-carbohydrate lunch meal (~2.2 g/kg carbohydrate; 35% estimated energy requirements) 2.5 hours prior.; Sixty minutes of cycling at 60% VO2peak will take place on a stationary bicycle ergometer at 16:00, after having skipped lunch, and having consumed nothing other than plain water since breakfast (08:00; 25% estimated energy requirements). Exercise will therefore commence after an 8 hour period of fasting.
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: The study design is a randomised, controlled, crossover design in which participants undertake three exercise conditions in a randomised order with at least a seven day period in between trials.
Masking: Single (Participant)
Primary purpose: Basic Science
Keywords: Fasted exercise; Low-carbohydrate; High-protein; Appetite; Energy Intake; Metabolism