Press Release2021.1.8｜International Institute for Integrative Sleep Medicine (WPI-IIIS)

Beating the Bulge with a Nice Cup of Tea
Researchers led by the University of Tsukuba find that drinking two cupsof oolong tea a day can stimulate fat breakdown while you sleep
Tsukuba, Japan - Does losing weight while you sleep sound too good to betrue? According to a study by the University of Tsukuba, it seems thatdrinking oolong tea might help you do just that. While all tea comes fromthe same plant, Camellia sinensis, the degree of oxidation, a chemical
reaction that turns tea leaves black, defines its specific type. For example,green tea is unoxidized and mild in flavor, while the distinctive color of
black tea comes from complete oxidation. Oolong tea, being only partially
oxidized, lies somewhere in between and displays characteristics of bothgreen and black tea. But while green tea is lauded for its health benefits,oolong tea remains more of an unknown.
"Like all teas, oolong contains caffeine, which impacts energy metabolism
by increasing our heart rate. However, studies suggest that tea
consumption may also increase the breakdown of fat, independent of theeffects of caffeine," explains senior author of the study Professor Kumpei
Tokuyama. "We therefore wanted to examine the effects of oolong
consumption versus caffeine alone on energy and fat metabolism among agroup of healthy volunteers."
Publishing their results in a recent issue of the journal Nutrients, theresearchers found that both oolong tea and pure caffeine increased fat
breakdown by about 20% in the healthy volunteers compared with theplacebo, and that oolong tea continued to have an effect while theparticipants were asleep. Interestingly, neither treatment caused anincrease in energy expenditure, indicating that the volunteers developed atolerance to the stimulatory effects of caffeine over the 2-week study
period.
Because a lack of sleep can impact energy metabolism, and because
caffeine is known to inhibit sleep, the researchers also studied the sleep
patterns of the volunteers. Significantly, there was no noticeable
difference in sleep patterns or the time it took participants to fall asleep
between the treatment and placebo groups, indicating that drinking
oolong tea is unlikely to prevent you from getting a good night's rest.
So should we all be downing copious cups of oolong tea to counteract theindulgences of the festive season?
According to Professor Tokuyama, the answer is maybe. "The stimulatory
effects of oolong tea on fat breakdown during sleep could have real clinicalrelevance for controlling body weight. However, we need to determine
whether the effects we observed in the 2-week study translate into actual
body fat loss over a prolonged period. In addition, we want to trial adecaffeinated oolong tea to better distinguish the effects of caffeine fromother components of tea, which will help us understand exactly how oolong
helps with fat breakdown."
About IIIS
IIIS was launched by the Ministry of Education, Culture, Sports, Science andTechnology of Japan with the aim of building globally visible research
centers with high research standards and excellent research environments
to accommodate globally prominent researchers. IIIS is the world’s premierinstitute aiming to elucidate the fundamental principles of sleep/wakebiology, develop new strategies to diagnose, prevent, and treat sleep
disorders, and contribute to promote human health through research
activities. The research was funded by the Japan Society for the Promotionof Science and the Japan Science and Technology Agency.

Bibliographic information
Zhang S, Takano J, Murayama N, Tominaga M, Abe T, Park I, Seol J, Ishihara A, Tanaka
Y, Yajima K, Suzuki Y, Suzuki C, Fukusumi S, Yanagisawa M, Kokubo T, and Tokuyama K,(2020) Subacute Ingestion of Caffeine and Oolong Tea Increases Fat Oxidation without
Affecting Energy Expenditure and Sleep Architecture: A Randomized, PlaceboControlled, Double-Blinded Cross-Over Trial.
Nutrients
doi: 10.3390/nu12123671
Media Contact
Alliance and Communication Unit, International Institute for Integrative Sleep Medicine(WPI-IIIS), University of Tsukuba, Japan
E-mail: wpi-iiis-alliance@ml.cc.tsukuba.ac.jp