I personally think the position of the dot hurts the name a bit, as far as "no fat" is concerned. If I were gonna start a diet website or what not I'd aim for a better name, personally. In fact I'm not sure if I'd give nof.at too much consideration.
But its a 3 letter domain and NOF could stand for whatever.
Anyways, the name 'nofat' is available for many TLD extensions, and IMO I'd prefer that to nof.at, for example nofat.ca, nofat.tm, nofat.sh,
Searching eNom I see that nofat.kids.us is available as well. Is that a new extension?
Anyways, I don't have much experience buying/selling domain names, take my input for what its worth