You must have been drinking around 2 litres of Coke for that many calories. Have you tried switching from Diet Coke to water? You'll need a few trips to Starbucks a day (an americano has 0 kcal, it's like caffeinated air!) until you can reduce your caffiene dependence.
Given the college or hacker environment, a six-pack or 2l over the course of 18 hours isn't a lot to drink. Healthy, no, but then neither is doing a 12" pizza solo and that was pretty commonplace as well. Coffee shops didn't exist, and even if they did, it's hard to beat a quarter a can. Hacking without caffeine? Gunna take a while...