Step number 1: Believing that these food items are bad and that they cause obesity, hypertension, coronary heart diseases, other health and psychological problems.
Step number 2: Understand that we don't eat them for their taste but for other reasons.
If you don't believe me remember the times when you were very hungry and rushed into one of these fast food restaurants and you ordered the meal that you like and you ate it so quickly that you didn't have the time to completely taste it.
Step number 3: Use alternatives to these food items.
I will explain steps 2 and 3 together in order to tell you the real reasons persuading us to eat these food items and the alternatives that you will use for these reasons.
Firstly, one of the important reasons that we eat sugary food is that these food items increase serotonin levels immediately in the brain.
Serotonin is the neuro transmitter of happiness sensation.
A better alternative for this effect would be eating fruits like oranges, apples and berries.
In addition to being healthy foods, fruits also contain sugars which will in turn increase the levels of serotonin and consequently make you feel happy.
Secondly, Junk and fatty foods increase the levels of fat in blood which in turn stimulates secretion of endorphins (natural analogues of Morphine and Heroine found in our bodies which makes us feel happy).
So these foods give you two things.
Firstly, they fill up your stomach and secondly increase fat levels in blood.
Thus the alternative would be something(s) that compensate for the two things.
The first alternative is filling your stomach with other healthy food like vegetables.
The second alternative (which you will use together with the first one and is much more important) is that you will exercise regularly.
But what exercise has to do with this? Exercise will lead to fat breakdown from your body and so the fat level in the blood will increase (same as after a junk or fat meal) leading to an increase in Endorphins.
Step 4: Psychological coping and media programming.
All the day you will find advertisements for this kind of food items.
These advertisements are in the television, newspapers, in the streets, in your work and nearly every where so you are always seeing these types of food so your mind will be programmed to buy them.
But it is possible to stop this programming.