Green Tea Increases Weight Loss during Caloric Restriction in Rats

The catechins in green tea are not the only healthy polyphenols of tea. (Photo by Augapfel)

It's time for some more green tea news from the weight loss frontier. If you're planning on doing calorie restriction to lose weight, you might want to consider adding green tea to your daily menu.

In a recent study, Sogawa et al. compared the anti-obesity effects of two types of tea, green tea and Awa tea, on male rats. The rats were first put on a weight-gain phase, where they were fed good old lard along with their standard diet. Then, they were put on a 50% calorie restriction (CR) diet to induce weight loss. During the CR diet, the experimental groups were supplemented with 3% green tea extract or 3% Awa extract, while the control group was given no supplements.

Awa tea is a traditional tea from the Tokushima prefect in Japan. It is made by fermenting tea leaves with lactic acid bacteria. Interestingly, this results in a tea with less catechins than green tea but with a similar polyphenol content, which means that catechins are just one type of polyphenols in tea.

Results

During the calorie restriction period, all three groups lost a significant amount of body weight. The green tea and Awa tea groups lost ~25% more weight than the control group, with no difference between the two types of tea.

Body fat ratio remained the same in the control group but decreased by ~10% in both tea groups. Green tea and Awa tea supplementation also reduced visceral fat accumulation compared to the control diet.

Plasma insulin levels were slightly lower in the tea groups, but the difference was not statistically significant. This is interesting, since green tea has been shown to increase insulin sensitivity both in vitro and in healthy humans during exercise. On the other hand, plasma leptin, which is also associated with body weight and fat ratio in humans, was significantly lower in both tea-supplemented groups.

Conclusion

Calorie-restricted rats supplemented with green tea and Awa tea lost more weight and fat mass than non-supplemented rats. Green tea and Awa tea also decreased plasma leptin concentrations. No significant differences were seen between the two types of tea, suggesting that other polyphenols than catechins (which are mainly found in green tea) also have health benefits.

Although fat intake was similar in all three groups, rats supplemented with tea had larger amounts of fecal lipids, which suggests that green tea and Awa tea effectively inhibited the fat absorption rate.

For more information on green tea and weight loss, see these posts:

Green Tea Extract Enhances Abdominal Fat Loss from Exercise
Drinking 3 Cups of Green Tea Increases Plasma Antioxidant Activity in Humans by 12%
Green Tea Extract Increases Insulin Sensitivity & Fat Burning during Exercise
Green Tea Protects from Bone Loss in Female Rats