Another important thing to keep an eye on is if you train regularly (i like to do weights one day cardio the next all week) if you have to miss a day for some commitment there is a temptation to cut down on how much you eat that day because you feel like your only maintaining your fitness by the exercise/food balance, if you miss the exercise you want to cut out the food to compensate. A common problem that isn't any good for you at all.
The key is to eat healty and exercise regularly, making sure to keep them distincintly seperate. Simply not eating kebabs is not going to get you healthy and fit, the same as cycling everyday and having takeaway everynight is not going to help you either.
Depends on how much exercise you do as well. During basic for the Army, I was eating rubbish - in quite large portions! Whenever a healthier option was on the table I would go for that, but often we were last in the cookhouse and ended up with pizza, chips, sausages, curries and generally less healthy options. I was also snacking on chocolate bars and sweets during the evening. Since we were being run ragged most days, with PT for at least a couple of hours each day, I was shedding weight at a pretty rapid rate!
But yeah, a little exercise daily and rubbish food isn't going to be of any benefit. I suspect it may be worse because people may think 'oh, well I go for a half hour jog every few days, this chocolate cake will just get burned straight off!' and justify eating more rubbish because they do some exercise. My wife is terrible for that!