Can tea help to reduce weight?

Yes!

The weight reducing effects of tea have long been recognised in traditional Chinese medicine.

Over the last 30 years, scientists have been analysing the active chemical compounds in teas in laboratories to document these effects biologically.

The results are consistent: tea consumptions are associated with weight loss, whether it is green tea, white tea, Oolong tea, black tea or pu-erh tea.

References:

Wolfram S, Wang Y, Thielecke F. Anti-obesity effects of green tea: from bedside to bench. Mol Nutr Food Res. 2006 Feb;50(2):176-87.
Lin JK, Lin-Shiau SY. Mechanisms of hypolipidemic and anti-obesity effects of tea and tea polyphenols. Mol Nutr Food Res. 2006 Feb;50(2):211-7.
Kuo KL, Weng MS, Chiang CT, Tsai YJ, Lin-Shiau SY, Lin JK. Comparative studies on the hypolipidemic and growth suppressive effects of oolong, black, pu-erh, and green tea leaves in rats. J Agric Food Chem. 2005 Jan 26;53(2):480-9.
Chiang CT, Weng MS, Lin-Shiau SY, Kuo KL, Tsai YJ, Lin JK. Pu-erh tea supplementation suppresses fatty acid synthase expression in the rat liver through downregulating Akt and JNK signalings as demonstrated in human hepatoma HepG2 cells. Oncol Res. 2005;16(3):119-28.
Yang TT, Koo MW. Hypocholesterolemic effects of Chinese tea. Pharmacol Res. 1997 Jun;35(6):505-12.
Yang TT, Koo MW. Chinese green tea lowers cholesterol level through an increase in fecal lipid excretion. Life Sci. 2000;66(5):411-23.
Lin YS, Tsai YJ, Tsay JS, Lin JK. Factors affecting the levels of tea polyphenols and caffeine in tea leaves. J Agric Food Chem. 2003 Mar 26;51(7):1864-73.
Bell SJ, Goodrick GK. A functional food product for the management of weight. Crit Rev Food Sci Nutr. 2002 Mar;42(2):163-78.