I'm in in a similar situation. I work two jobs plus school which means I'm away from home 14 to 16 hours every week day. A year ago I was a flabby 250 lbs. Today I'm a fit 180 lbs (I'm 6'3"). How? First, if you're not working out as much you should be eating less. I have a program on my Treo that I use to track my daily caloric intake and expenditures. If weight is your biggest concern, that's all you need. Seriously, your metabolism has nothing to do with it. Eventually you'll get used to the right amount of food for your activity level and you can stop counting every calorie.
If you're also looking to be fit you should sneak in a little bit of exercise. For me, I do pushups, situps, and pullups every morning. It only takes maybe 10 minutes to do, which anyone can fit into their morning routine. I have an exercise ball for the situps and a bar for the pullups - less then $50 for the whole setup. I also go to the gym every Saturday in the early afternoon. I'm usually still exhausted from the week, so I never make this trip optional for myself.
That's it. It really is just a matter of squeezing a few minutes a day and watching what you eat. Good luck.