Green Tea Benefits on Metabolism

Last Updated: Aug 16, 2013 | By Michele Turcotte, MS, RD Green Tea Benefits on Metabolism


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 are vast and include cancer prevention and a decreased risk of cardiovascular disease. There is another important benefit of green tea. In many research studies, green tea extract has been shown to significantly alter body composition by increasing metabolism.

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 as few as three glasses of green tea daily can contribute to a reduction in body weight and weight circumference (women with a waist of more than 35 inches and men with a waist of more than 40 inches are at a much greater risk of cardiovascular disease than their slim-waisted counterparts) by almost five percent in three months. Catechins are found in green tea (one cup offers 142 milligrams), chocolate (four ounces offers 53 milligrams) and black tea (one cup 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 of caffeine and 90 milligrams of EG), caffeine (50 milligrams) and placebo. The conclusions of this study were that green tea promotes fat oxidation beyond that which could be explained by its caffeine content.

Physical Activity Increases Effect

A study published by the Journal of Nutrition revealed that consumption of green tea catechins enhances exercise-induced changes in abdominal fat and serum triglyceride (blood fat) levels. One-hundred thirty two (132) participants were randomly assigned to two groups. The first group were given a beverage containing 625 milligrams of catechins and 39 milligrams of caffeine, while the second group were given a control beverage (39 milligrams of caffeine, no catechins) over a 12-week period. Their diets remained constant but they participated in at least 180 minutes per week of moderate-intensity exercise.

Body composition, abdominal fat and serum triglyceride levels were measured at baseline and after 12 weeks. There was significantly greater weight loss, 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 which would lead to specific recommendations.