Is there any diet beer? I want to drink beer because I feel stress of my life. However, I don't want to gain weight because I have been overweighted. Is there any diet beer in US?
This is what would be referred to as the "Light Beer" category. For the most part, this is mass-produced beer, done by the big commercial breweries in the USA (I don't know much about beer production outside North America).

If you want some good light beers, I'd suggest taking a look at lists like BeerAdvocate's Best Light Lagers