Recent studies have shown that drinking green tea may help increase bodyfat oxidation, and one shows that oolong tea may do the same.1 In the new study 12 men drank each of four treatments: 1) water; 2) full-strength oolong tea, brewed from 15 grams of tea leaves; 3) half-strength tea, brewed from 7.5 grams of tea leaves; 4) water containing 270 milligrams of caffeine, or about the dose of caffeine found in full-strength tea or two cups of brewed coffee.
The subjects drank the tea in five daily doses for three days. Energy expenditure was measured on the third day. Testing showed an increase in energy expenditure of 2.9 percent for the full-strength tea and 3.4 percent for the caffeinated water treatments. Fat oxidation was 12 percent higher in those drinking the tea than in those drinking the water alone (without caffeine).
At first glance this study of the antiobesity effects of oolong tea doesn't seem too impressive, since the caffeinated water showed a greater effect on increasing metabolism; however, a study that looked at the fat-reducing effects of oolong tea sheds more light on the subject. It was published two years ago and featured rats as subjects.2 For 10 weeks the rats were placed on a high-fat diet containing 40 percent beef tallow, a saturated fat known to increase bodyfat levels through such mechanisms as insulin resistance. The rats given oolong tea along with the high-fat diet showed a preventive effect against added bodyfat accretion, while those not provided with the tea showed increased bodyfat levels.
While most of the fat-reducing effect was attributed to a caffeine-induced release of norepinephrine, a hormone that leads to bodyfat mobilization, the tea also had an inhibiting effect on the secretion of lipase, an enzyme produced in the pancreas that's needed for fat absorption. That's the same enzyme partially inhibited by Orlistat, a popular antiobesity drug. Significantly, caffeine doesn't have that effect on lipase, although green tea does.3
This information shouldn't be interpreted as an invitation to indulge in high-fat meals with impunity. The effect of oolong tea is slight'but helpful'and won't overcome the effects of eating too much or exercising too little.
1 Rumpler, W., et al. (2001). Oolong tea increases metabolic rate and fat oxidation in men. J Nutr. 131:2848-2852.
2 Han, L.K., et al. (1999). Antiobesity action of oolong tea. Int J Obesity. 23:98-105.
3 Juhel, C., et al. (2000). Green tea extract inhibits lipolysis of triglycerides in gastric and duodenal medium in vitro. J Nutr Biochem. 11:45-51.