You won't get fat, because most herbal teas have the effect of clearing away heat and toxic materials, and it has nothing to do with being fat.

Some herbal tea effects:

Juice black tea has the effect of removing fire and refreshing.

Mint herbal tea can refresh your mind.

Chrysanthemum Sydney tea has the effects of clearing away heat and toxic materials, expelling wind and dissipating heat.

Bitter summer herbal tea can prevent sore throat.