The Effect of Green Tea Supplementation Strategies on Fat Oxidation and Body Composition in Overweight Individuals
Trial Snapshot
- Phase
- Not Applicable
- Status
- Completed
- Sponsor
- Anglia Ruskin University
- Enrollment
- 30
- Locations
- 2
- Primary Endpoint
- Fat oxidation (max)
Study Overview
Brief 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?
Study Design
- Study Type
- Interventional
- Allocation
- Randomized
- Intervention Model
- Parallel
- Primary Purpose
- Basic Science
- Masking
- Double (Participant, Investigator)
Masking Description
Nutritional supplements will be provided in a randomised, double-blinded manner. Both the participants and research testers will be masked from knowing the specifics of the supplement intervention.
Eligibility Criteria
- Ages
- 18 Years to 55 Years (Adult)
- Sex
- All
- Accepts Healthy Volunteers
- Yes
Inclusion Criteria
- •Men and women, UK based, above 18 years of age
- •Below 45 years of age (for men) and below 55 years of age (for women)
- •Baseline maximal oxygen uptake >25ml/kg/min and <45ml/kg/min representative of normal (but not high) fitness levels; and a body mass index (BMI) >25kg/m2 and <33kg/m2
- •All participants: No known history (including family history) of heart abnormalities, hypertension, coronary heart disease or diabetes (determined from pre-study health screen questionnaire)
- •All participants: No known history of liver related disorders (e.g. hepatitis, Wilsons disease, cirrhosis).
- •All participants: Not currently suffering from any musculo-skeletal injury, or any other reason that may prevent participation in cardiovascular exercise
- •All participants: Have not suffered from recent viral infections ie: influenza (defined within the prior 2 months)
- •All participants: Not suffering from any known blood related disorders, including blood coagulation abnormalities, or have any adverse reactions to blood taking
- •All participants: Not taking any prescribed or over-the-counter medication which may influence exercise training (with the exception of inhalers for exercise induced asthma or contraceptive pill)
- •All participants: Not consuming or prepared to refrain from consumption, any commercial supplementation which conflicts with the study parameters ie: creatine, other green tea or weight loss products.
Exclusion Criteria
- •Anyone below the age of 18 years, or above 45 years (for men) and 55 years (for women) - based on exercise testing guidelines by the American College of Sports Medicine (ACSM).
- •Those who do not meet the criteria for baseline maximal oxygen uptake or BMI assessment
- •All participants: anyone with a known history (including family history) of heart abnormalities, hypertension, coronary heart disease or diabetes (determined from pre-study health screen questionnaire)
- •All participants: anyone with a known previous history of liver related disorders.
- •All participants: Anyone suffering from a current musculo-skeletal injury, or any other reason that may prevent participation in cardiovascular exercise
- •All participants: those suffering from recent viral infections ie: influenza (defined within the prior 2 months)
- •All participants: Those with known blood related disorders, including blood coagulation abnormalities, or have any adverse reactions to blood taking. This includes any participant who has or potentially has an infectious disease, inc. HIV, and all types of hepatitis.
- •All participants: Anyone taking any prescribed or over-the-counter medication which may influence exercise training (with the exception of inhalers for exercise induced asthma or contraceptive pill)
- •All participants: Anyone consuming or not prepared to refrain from consumption, any commercial supplementation which conflicts with the study parameters ie: creatine, other green tea or weight loss products.
- •FEMALE ONLY: Any participant who is, suspects they may be or becomes pregnant during the study.
Outcomes
Primary Outcomes
Fat oxidation (max)
Time Frame: Change from Baseline maximal fat oxidation at 2 months
Assessment of maximal fat oxidation rate (via expired air) during incremental exercise
Fat oxidation (min)
Time Frame: Change from Baseline minimum fat oxidation at 2 months
Assessment of exercise intensity at which point fat oxidation is negligable
Secondary Outcomes
- Blood glucose(Change from Baseline blood glucose at 2 months)
- Height(Change from baseline height at 2 months)
- Weight(Change from baseline weight at 2 months)
- Bodyfat percentage(Change from baseline bodyfat percentage at 2 months)
- Central abdomen depth(Change from baseline central abdominal depth at 2 months)
- Blood insulin(Change from Baseline blood insulin at 2 months)
- Blood leptin(Change from Baseline blood leptin at 2 months)
- Blood adiponectin(Change from Baseline blood adiponectin at 2 months)
- Blood liver enzymes(Change from baseline at 2 months)
- Blood bilirubin(Change from baseline bilirubin at 2 months)
- Respiratory measures (oxygen, carbon dioxide) during steady state exercise(Change from baseline at 2 months)
- Waist to hip ratio(Change from baseline waist to hip ratio at 2 months)
- Body mass index(Change from baseline BMI at 2 months)
- Blood cholesterol(Change from Baseline at 2 months)
- Blood fatty acids and glycerol(Change from Baseline at 2 months)
Investigators
Justin Roberts
Associate Professor
Anglia Ruskin University