the idea is to never stop the diet. Once you start it, you just continue. For the rest of your life.
That is actually not as bad as it sounds. The word "diet" does not mean you should starve yourself, even though that is what most people perceive as the only meaning of the word, reducing "diet" to "weight loss".
Deliberately starving yourself is necessary at the beginning, when you actually reduce your weight. Be careful during that period, however. Dont go too low on calories, mind the essential stuff (some fatty acids, proteins, vitamins) and try to avoid pushing your metabolism into an emergency mode. When in doubt, consult a medic. When not in doubt, make sure you know what you are doing - after all, when everybody gets nervous but one person stays cool it may as well be that this person has not yet grasped the whole situation
After reaching your desired weight you get to another aspect of "diet", i.e. control your eating habits. Maintain an intake of an appropriate amount of reasonably healthy food. It does not mean to eat less, it means to eat not(!) more than you actually need. This means: Change your eating habits. If you go back to your old habits you will re-gain your old weight. Just like you initially gained your overweight you are (again?) working so hard to get off.
McD, Burger K*ing etc are too high caloric to maintain any weight. Just get your priorities right. Eating there is OK if you think you really need it, and if you do it much less frequent than before. Try poultry (without the skin), lean beef, veggies, salad. Avoid pork, fat in any form (mind the essential fatty acids, though, since you need these), plain sugar and high caloric snacks. Avoid highly processed food in general.
Whatever you do, constantly control your weight so you can immedaitely counter any new weight gain.
If you like to do some no-nonsense reading on the topic try "Hackers Diet" from John Walker (for the IT guys among you, this is the man who developed AutoCAD). You will find it here:http://www.fourmilab.ch/hackdiet/
Good luck. For beer-drinking, BBQ loving me it worked - and continues to work - unexpectedly well