Because your body is probably addicted to sugar. Its not always a motivation issue. Instead of shunning food, eat a lot of healthy stuff before you go to the junk food. Naturally you'll cut down on the bad stuff by filling yourself up beforehand. <br />
Food can be viewed the same as drugs. You can't go cold turkey or your body will freak out. I'm sure you've noticed its not natural to be thinking about junk food all the time when you're trying to ignore the hunger pangs. Most people have a psychological dependence on food, you need to break it gradually or you'll fail. That's why 90% of diets don't work.
Relax. It's only junk if you say its junk. If a salt laden, fatty, carb, with little recognized nutritional value excites your inner glutton -- it must actually be health food for part of you. Hey, learn to rationalize your eating habits better and the Wall Street Food Gurus will loose their grip on you. Then you can choose, and eventually, you will win without the guilt laden advise of those who want to sell health.
Because it tastes good?
Heh. I do the same if I have junk to pig out on, which most of the time I don't. Staying up late is BAD for one's physique.
How can work be healthy. <br />
The thought of it makes me ill !
It's a choice you chose to make, it may have started out as a habit. I think it's best you make a routine in which at this moment of time you do something that distracts you from food.<br />
Ex. When you feel hungry, fill yourself with water, or do some meditation and writing.