I agree with the valuation consensus. Low to mid $X,XXX reseller, low $XX,XXX end user. I think it works better in the US market than the UK but that's not a bad thing because the US market drives domain value.
In the US fatness is regarded as a medical condition but in the UK it is used in a derogatory, belittling, or insulting manner. The Scottish character "Fat Bast$%d" in the Austin Powers movies or the "Fat Slags" in the UK magazine Viz sum up the word use here. I don't think somebody who has been taunted by chants of "Who Ate All The Pies?" would take much pleasure visiting Fat.info.
I registered Slimming.pro last Thursday, I was specifically targeting UK-centric keywords. Slimming has 29,300 UK Overture searches compared to 11,800 for Fat but for the US Overture it's a landslide 116,300 search results for Fat versus 8,100 for Slimming. The .pro bun has just gone in the oven value wise but .info is cooking nicely, especially recently.
The only minor niggle is that although the keyword is strong in the US, resellers there have been slow to accept .info and that has held down valuations. I went through a spell of buying .infos and always targeted US registered .infos because Europeans were unrealistic on price.
Judging by the 39 offers you've received on Sedo, applying for this keyword through the second .info landrush was a very smart move. Good luck with the sale.