You might try checking with the Vegetarian Society of DC (VSDC) -- www.vsdc.org -- You might consider contacting them via e-mail (their address is on the website).
We've done some web searches and located some vegetarian restaurants in the Washington, D.C. area, but since most of them are Indian, we suspect it will be difficult to find low-fat or no-fat fare. Do any of you who live in the D.C. area or visit there often have favorite restaurants that serve at least some fat-free vegetarian dishes?