Low Versus High-glycemic Index Post-exercise Diets for Improving Metabolism and Body Composition
Condition: Hypercholesterolemia
MeSH terms: Hypercholesterolemia
Study type: Interventional

Summary: 
      Postprandial triglycerides are a strong risk factor for heart disease. The purpose is to
      assess the effects of a low-glycemic versus high-glycemic meal after 90 minute exercise
      sessions that are done 4 times a week for 6 weeks on postprandial triglyceride level.
      Secondary measurements include other lipids and body composition.
    

Detailed description: 
      The increase in triglycerides after a meal (i.e. postprandial triglycerides) is a strong risk
      factor for cardiovascular disease. Overweight/obese individuals have a greater triglyceride
      response to the same meal compared to lean individuals; therefore they are at greater risk.
      If exercise is performed the evening before a high-fat breakfast, the postprandial levels of
      triglycerides after the breakfast are reduced; however, if high glycemic index (GI) foods are
      consumed after the exercise session, the benefits of exercise on next-day postprandial
      triglycerides is negated. The investigators recently showed (HSFC funded) that consuming low
      GI foods after exercise is similar to fasting after exercise and superior to consumption of
      high GI foods for lowering next-day postprandial triglycerides. Low GI food was also superior
      for increasing fat oxidation, and lowering insulin, and low and very low density lipoproteins
      and preventing a decrease in high density lipoproteins. The benefits of an acute exercise
      session followed by low GI food consumption is now clear; however, it is not known whether
      this practice over weeks of exercise training results in accumulated and sustained benefits.

      The purpose of this study is to determine the chronic effects of consuming low compared to
      high GI foods after exercise sessions over six weeks in overweight and obese individuals.

      Twenty-four overweight and obese males and females will be randomized to consume either high
      or low GI foods immediately after exercise sessions (four sessions per week, 90 minutes per
      session, six weeks). At all other times of the day over the six weeks, they will be supplied
      a moderate GI diet, with calories and macronutrients based on four-day food diaries completed
      before the study. Two weeks before the intervention, participants will be required to go on
      the moderate GI diet, as a lead-in. One week into the lead-in, a baseline test will be done
      to determine postprandial metabolic responses (i.e. triglycerides, low and very low density
      lipoproteins, high density lipoproteins, insulin, and fat oxidation) after a morning high-fat
      breakfast. A week later, the same postprandial testing will be carried out the morning after
      the first exercise and post-exercise consumption of a low or high GI recovery meal.
      Participants will continue the training and post-exercise food consumption for the next six
      weeks, with postprandial measures taken again following the final exercise and feeding
      session. Body composition and aerobic fitness will be determined before and after the six
      week intervention.

      The investigators hypothesize that the low GI post-exercise feeding will be superior to the
      high GI post-exercise feeding for reducing body fat, improving fat oxidation, and reducing
      postprandial triglycerides, insulin and other harmful lipids. The results of the study will
      provide clinicians, exercise professionals and dietitians unique and experimentally tested
      strategies for their clients to lose body fat and improve metabolic profiles, to reduce the
      risk of heart disease.
    

Intervention name(s): Low glycemic index post-exercise diet; High glycemic index post-exercise diet
Intervention type(s): Dietary Supplement; Dietary Supplement
Intervention description(s): Feeding of a low-glycemic index, lentil meal after 90 minutes of walking exercise; Feeding of a high-glycemic index meal (i.e. instant mashed potatoes, white bread, egg whites) after 90 minutes of walking exercise
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Prevention