Soibhan

I am certainly no expert, but I've never heard of an acid in tea that would cause a 'spare tire' around your middle. Tea has antioxidents which are helpful to the immune system and help to prevent aging. As long as you don't sweeten with sugar (use some lemon and perhaps Splenda, if you want sweetness) and you should be fine.
Soibhan
p.s. You can always do a search on the properties of tea.