The tea plant is naturally high in a group of antioxidants known as catechins. Green tea offers more catechins than black tea because its production involves less processing and fermentation. The health benefits of green tea include cancer prevention and a decreased risk of cardiovascular disease. In many research studies, green tea extract alters body composition by increasing metabolism. However, this is not conclusive as some studies have shown no effect.
How Can Catechins Aid in Weight Loss?
Catechins are powerful antioxidants that may aid weight loss in two ways. They inhibit the breakdown of fats and the production of an inflammatory substance that triggers hunger. Drinking three glasses of green tea daily can help reduce both body weight and waist circumference (women with a waist of greater than 35 inches and men with a waist of greater than 40 inches are at a significantly greater risk of cardiovascular disease then their slim-waisted counterparts) by almost 5 percent in three months. Catechins are found in green tea (1 cup offers 142 milligrams), chocolate (4 oz. offers 53 milligrams) and black tea (1 cup black tea contains 27 milligrams). However, only green and black tea are calorie-free.
Green Tea Catechins and Fat Oxidation
A study published by the American Journal of Clinical Nutrition investigated whether the green tea extract (containing caffeine and the catechin known as epigallocatechin gallate, or EG), could increase 24-hour energy expenditure (EE) and fat oxidation (burning of fat) in humans. On three separate occasions, 10 healthy men were randomly assigned to receive one of the following at breakfast, lunch and dinner: green tea extract (50 milligrams caffeine and 90 milligrams of EG), caffeine (50 milligrams), and/or a placebo. The conclusions of this study were positive in that green tea helps promotes fat oxidation beyond that which can be explained by its caffeine content.
Physical Activity Increases Effect
A study published by the Journal of Nutrition suggests that consumption of green tea catechins enhances exercise-induced changes in abdominal fat and serum triglyceride (blood fat) levels. One-hundred thirty-two participants were randomly assigned to two groups. The first group received a beverage containing 625 milligrams of catechins and 39 milligrams of caffeine, while the second group received a control beverage (39 milligrams of caffeine, no catechins) over a 12-week period. Their diets remained constant but they participated in greater than or equal to 180 minutes/week of moderate-intensity supervised exercise.
Body composition, abdominal fat and serum triglyceride levels were measured at baseline and after 12 weeks. There was significantly greater weight loss, and percent change in total abdominal fat, subcutaneous abdominal fat and fasting serum triglyceride levels in the group that consumed the catechin-rich beverage. While this evidence appears convincing, many more studies are needed to draw conclusions that would lead to specific recommendations.
References
- International Journal for Vitamin and Nutrition Research; Health Potential for Functional Green Teas; N Boon; Dec 2008
- American Journal of Clinical Nutrition; Efficacy of a Green Tea Extract Rich in Catechin Polyphenols and Caffeine in Increasing 24-h Energy Expenditure and Fat Oxidation in Humans; AG Dulloo, C Duret, D Rohrer, et al.; Dec 1999
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