Oolong tea shown to promote weight loss
The Chinese believe that drinking tea promotes good health and longevity. This belief is gaining some scientific merit in recent years. Oolong tea is one of three types of tea manufactured from tealeaves. The other types are black and green teas. Oolong tea is less fermented than black tea and is served commonly in Chinese restaurants and sold commercially in the United States. Oolong tea has been researched for its antioxidant properties, it's effects on cardiovascular disease, cancer and obesity. There is some data to suggest that oolong tea may promote weight loss through increasing energy expenditure (EE). Caffeine itself is known to increase EE for several hours following ingestion, depending on the level of intake. Oolong tea contains significant amounts of caffeine. It is unclear whether the increase in EE that accompanies the consumption of oolong tea is solely due to caffeine or to other constituents such as polyphenolic compounds.
In order to further investigate this relationship, researchers recruited twelve men between the ages of 25 and 60 years to participate in a randomized, cross-over design study. Subjects were randomly assigned to one of three cohorts of four subjects. A treatment consisted of a beverage consumed five times daily containing one of four test beverages; water. water plus caffeine (270 mg caffeine per day), half-strength tea (brewed from 7.5 grams of tea) and full strength tea (brewed from 15 grams of tea). The water plus caffeine beverage was formulated to contain the same amount of caffeine as the full-strength tea treatment. Subjects received each treatment for three days. On the third day, EE was measured by indirect calorimetry, in a room calorimeter. For the three-day test periods, the subjects consumed a typical American diet. Energy content of the diet was specified for each subject's needs as determined from a preliminary, measure of 24-hour EE by calorimetry.
It was found that EE significantly increased by 2.9 percent for the full-strength tea and 3.4 percent for the caffeinated water treatments. This increase resulted in an additional expenditure of 281 kJ/day for the tea and 331 kJ/day for the caffeinated water. Additionally, fat oxidation was significantly higher (12%) when subjects consumed the full-strength tea rather than the water. Fat oxidation was higher with the full-strength tea than with the caffeinated water.
Researchers suggest that an unclear compound in oolong tea, other than the caffeine, increase fat oxidation and may help to promote weight loss. Further, more large-scale investigations are needed to clarify the relationship between tea and weight loss.