I am inclined to agree with Brandis by taking a gentle approach.
But my idea is this if you want to consider giving it a go.
1. read the book french women don't get fat. Read it more for motivation, good ideas and good sense and to learn about how food can equal pleasure without pain.
2. Weigh yourself first thing tomorrow morning, figure out your maintenance calories based on no exercise and your current weight using an online calculator
3. Decide to try to eat up to those calories every day. This will enable you to avoid hunger.
4. in the three months leading up to your start date, work on improving the quality of the foods you eat. Do that by increasing your fruit and vegetables and reducing your refined carbs, processed foods, junk foods, takeaway foods. If you want a lot of calories you can top them up with quality cheese, nuts and seeds in addition to the other whole foods you are eating more of rather than all the stuff that causes cravings and regrets.
5. Develop your cooking skills. Don't go for fancy stuff. Focus first and foremost on cooking vegetables in interesting ways. They can be mixed with meats but start with your veggie foods. I mean don't start by saying i'm having chicken for dinner how to cook it with vegies start by saying, i've got aubergines and zucchinis, how'm i going to cook it. My hint is to experiment with mediterranean foods - greek, french, spanish, italian, as your first because of all the exotics its probably closest to the way most westerners eat most of the time. And then branch out into into trying middle eastern, indian, and other asian cuisines, not to mention south american. Try to learn how to cook beans and lentils and have a few meals based on those each week because they are high in protein and fibre and are very very good for you. Use recipes books or good online sites for your recipes. Don't think you have to make it all up all the time. Once you've used recipes a lot you get a feel for what's going to work.
7. When choosing recipe books, look for something that seems like it could be more traditional. Who's written it? Is it someone with a background or experience in that culture. Some food tv shows have websites with their recipes. In Australia SBS is one of our best for authentic recipes i think. Avoid the sort of cook books that seem to be straining after being restaurant degree fancy. Go for tradition instead
8. With your cooking, focus on savoury foods, avoid all the dessert things. You can come back to that in the future when you've made a lot more progress and you have trained yourself into better eating habits.
You probably didn't want all this advice. But well if you've been lurking, by now you must know that some of us love to give it. Its only because we want us all to succeed.
9. For sweetness to help minimise all the junky foods, eat a lot of fruit. And try stewing fruits like pears, apples, rhubarb, plums and other stone fruits. Make fruit salad or mix fruit into your savoury salads. You can afford to eat a a lot of fruit. It won't hurt you and when you severely cut down on the highly sweetened foods you buy, you will find the sweetness of fruit perfectly satisfying.