2. Black tea is cool and bitter, and has the functions of relaxing bowels, warming stomach and relieving pain, diuresis, promoting fluid production and clearing heat. You can usually drink black tea to lose weight. Black tea contains a certain amount of caffeine, which can excite brain nerves, promote blood circulation, decompose fat, help urination and eliminate edema. It should be noted that you should drink black tea in moderation, because black tea is cool, and if you drink too much, you are prone to abdominal pain, diarrhea, nausea and other symptoms.