Green tea extract together with exercise reduces abdominal fat. (Photo by mikebaird)
Whether or not drinking green tea helps with weight loss is not entirely clear, especially when it comes to humans. However, a new study by Maki et al. suggests that green tea does have a positive effect on overweight individuals.
Specifically, the authors report that the catechins in green tea enhance abdominal fat loss in obese adults who are put on an exercise program.
Exercise alone vs. exercise and green tea extract
All of the 107 participants who completed the 12-week study had a BMI between 25 and 40, which put them in the overweight category. They were randomly assigned to receive either a drink containing green tea extract and 625 mg of catechins or a control drink with no catechins. Both drinks had the same amount of caffeine.
The main catechins in the green tea drink were epigallocatechin gallate (EGCG) and epigallocatechin (EGC). The catechin distribution was similar to those found in normal teas, but the amount of catechins in the drink was much higher than in green tea, which has the highest catechin content.
The participants were also put on an exercise program with a goal of at least 3 hours of moderate-intensity physical activity per week. Diets did not change in either group, but caffeine intake was lower in both groups during the experiment.
Reduced abdominal fat and triglycerides in catechin group
The catechin group had a greater loss of body weight than the control group, but changes in waist circumference and fat mass percentage were not significantly different. However, total abdominal fat areas and abdominal subcutaneous fat areas were lower in the catechin group.
So what exactly happened here? As you can see from the figure above, both the group that received the green tea extract and the group that received the control beverage lost some fat mass during the experiment. That's to be expected, of course, since both groups got on an exercise program.
What's interesting is that even though both groups had the same level of physical activity, the green tea group lost more weight and more total fat mass (though the latter was not statistically significant). After 12 weeks, the average weight loss in the control group was 1 kg, while in the catechin group it was 2.2 kg. Nothing spectacular here, but still a noticeable difference.
If you look at the changes in the total abdominal fat area, you can see that there was almost no difference in the control group. That is, exercise alone did not reduce the total abdominal fat area. In fact, even though the intra-abdominal fat (the "dangerous one" around your internal organs) area decreased slightly, subcutaenous fat (the one just under the skin) area actually increased slightly.
Exercise with daily green tea extract on the other hand led to a 7.7% decrease in total abdominal fat area, with reductions in both subcutaneous and intra-abdominal fat areas. According to the authors, however, the difference in intra-abdominal fat area between the catechin and control groups was not statistically significant.
The participants in the catechin group also reduced their triglyceride levels more than the control group. Similar differences between groups were not seen in HDL and LDL levels. Fasting glucose and fasting insulin levels did not change during the study.
A daily beverage containing green tea catechins combined with moderate exercise was more effective in reducing abdominal fat in obese individuals than moderate exercise alone. Specifically, the total abdominal fat areas and abdominal subcutaenous areas were reduced in the catechin group.
For more information on green tea, see these posts:
Green Tea Increases Weight Loss during Caloric Restriction in Rats
Green Tea Extract Increases Insulin Sensitivity & Fat Burning during Exercise
Green Tea and Capsaicin Reduce Hunger and Calorie Intake
Green Tea, Black Tea & Oolong Tea Increase Insulin Activity by More than 1500%