I am going on a diet! HELP!! Where to eat?

There is a place with a yellow sign on Gurrachaga near the corner of Honduras - "Flores of something" I can't remember the name but its a dietetica and does organic/healthy/yummy food. They also do take away. Suerte!
Make your own food. Eat lots of fruit and vegetables. Drink lots of water. Walk as much as possible. Limit your pizza, empanadas, & beef.

That's all you need to do to seriously drop pounds. It's actually pretty darned easy and fairly frugal.
Undoubtedly the advise of Napoleon is excellent. If I wanted to lose weight, I´d stay away from away restaurant. Forget rice, pasta and bread. Eat foods that contain fiber. I´ve found that the best produce is sold on the streets by (mostly Bolivian) woman. Join a gym. If your destination is too far go by bicycle
Stop eating wheat. I can't eat wheat, and all the steaks in the world don't make a dent.

Unfortunately you also feel hungry all the time...