Green Tea Supplementation, Fat Oxidation and Body Composition in Overweight Individuals
Condition: Overweight and Obesity; Fat Burn
MeSH terms: Overweight
Study type: Interventional

Summary: 
      The purpose of this study is to investigate the effects of green tea extract (GTE) on fat
      oxidation, body composition and exercise performance in overweight individuals. The study
      will be conducted under laboratory conditions following an 8 week supplemental period.
      Participants will be required to attend the laboratory for a pre-screening/familiarisation
      trial followed by assessments at week 0 (baseline), week 2, 4 and 8. Across the intervention,
      participants will maintain habitual dietary intake and follow a prescribed exercise
      programme. Additionally participants will be randomised to either a placebo, green tea
      extract or GTE with antioxidant supplementation.

      It is hypothesised that the addition of antioxidants with GTE will enhance fat oxidation in
      overweight individuals more than GTE or placebo. It is further hypothesised that such
      improvements in fat oxidation due to GTE will lead to improvements in both body composition
      variables and submaximal exercise performance (metabolic efficiency) in overweight, but
      otherwise healthy persons.
    

Detailed description: 
      The health benefits of polyphenols found in green tea (GT), the unfermented leaves of the tea
      plant, Camellia sinensis, are of current scientific interest. These health benefits, in part,
      relate to the bioactive catechin polyphenol content of GT, of which
      (-)-epigallocatechin-3-gallate (EGCG) can account for between 50-80% of the total catechin
      content. GT catechins have been proposed to influence metabolic and thermogenic activities in
      the short term, leading to enhanced fat oxidation capacity, although this has been disputed.

      Research investigating GT extracts (GTE) and exercise have produced conflicting results.
      Modest EGCG dosage in the short term (270 mg·d-1 EGCG for 6 days, and 68 mg·d-1 EGCG for 3
      weeks) did not alter metabolic or performance variables in healthy or endurance trained
      volunteers. However, the inclusion of 100.5 mg·d-1 EGCG over a 10 week training period
      enhanced whole-body metabolic efficiency elsewhere. One confounding factor though is the use
      of caffeinated GTE in these studies. When decaffeinated GTE (dGTE) has been employed, 366 mg
      EGCG was found to acutely increase fat oxidation by 17%. Indeed a recent publication from our
      research group investigating the short term use of dGTE demonstrated positive changes in fat
      oxidation in healthy volunteers. However, less is known as to whether dGTE (or indeed
      combinations of dGTE with antioxidant nutrients which may improve GTE bioavailability) could
      provide similar results in overweight or sedentary individuals embarking on an exercise
      programme.

      The aim of this research proposal is therefore to assess the impact of two GTE strategies on
      fat oxidation, cardiometabolic health, visceral fat reduction, and exercise performance in a
      healthy, but overweight cohort undertaking a standardised exercise training programme.

      Research Questions:

      Q1: Does regular consumption of dGTE favourably enhance fat oxidation and/or improve
      variables associated with cardiometabolic health and body composition in comparison to a
      placebo supplement in healthy, but overweight individuals? Q2: Does a dGTE complex (including
      key antioxidant nutrients) enhance fat oxidation and/or improve variables associated with
      cardiometabolic health and body composition more so than dGTE or placebo supplementation in
      healthy, but overweight individuals?

      This study will involve participants attending sessions at Compass House, ARU, undertaking
      the following:

        -  Baseline trial: all participants will attend a subject briefing, provide written,
           informed consent prior to participation. Following this, all participants will undertake
           a baseline test for maximal fat oxidation rates (FATmax) and oxygen uptake using a
           standardised incremental cycling exercise protocol and expired air analysis

        -  Intervention period: participants will be randomly assigned to either dGTE (400mg EGCG
           daily), dGTE with antioxidants (150mg quercetin, 150mg alpha-lipoic acid) or placebo for
           8 weeks. During this period, participants will undertake regular aerobic exercise (3x/
           week; 45mins; at ~ FATmax intensity)

        -  Experimental evaluation of progress will be assessed at weeks 0,2,4, and 8. During
           laboratory visits, participants will be required to have a single venepuncture blood
           sample, assessment of blood pressure/ body composition (skinfold, bioelectrical
           impedance, waist circumference), assessment of FATmax, and assessment of fat oxidation
           during steady state exercise at FATmax.
    

Intervention name(s): Placebo control; GTE 1; GTE 2
Intervention type(s): Dietary Supplement; Dietary Supplement; Dietary Supplement
Intervention description(s): 8 week supplementation period, with participants consuming 2 capsules per day containing potato starch; 8 week supplementation period, with participants consuming 2 capsules per day containing green tea extract (571mg/d); 8 week supplementation period, with participants consuming 2 capsules per day containing green tea extract with additional antioxidants (150mg of quercitin and 150mg of alpha lipoic acid)
Other intervention name(s): Placebo; Decaffeinated green tea extract; Decaffeinated green tea extract and antioxidants
Intervention MeSH terms: Antioxidants
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: Participants randomly assigned to either placebo, green tea extract (GTE) or GTE with antioxidants in a parallel, double blind manner
Masking: Double (Participant, Investigator)
Primary purpose: Basic Science
Keywords: Green Tea; Exercise Metabolism