For the "math" part, I wrote this short blog post: http://www.hackersinshape.net/archives/109
Oh and the diet part will get you only so far and it is the most challenging part, but without exercise you are missing the big step in speeding up your metabolism that in return burns more calories and the combination which results in exponential results. (Leaner more muscular look. Unless you want you leftover skin to be hanging on the floor of course, I'd strongly recommend exercise as part of the program)
I weighed 85kg on +/-179cm with 25% body-fat. Year later, I weighed 73.5kg with 7% body-fat. Healthier I have ever been and am still sticking to it three years later. Here is my 1 year review: http://www.hackersinshape.net/archives/16
[edit] Know that there is no secret or any form of black magic :), its a combination of "a) some basic knowledge" (Know what you eating [1 avg. donut == +/-250 calories. That equates to about an hour of running.]), "b) smaller quantities of whole foods at more frequent intervals" and "c) exercise" (Both cardio and resistance).