Filling out a balance sheet on fast food is easy. The overabundance of calories, sodium, sugar, and fat alone will give you enough reasons to quit. Fast food's only real benefit is convenience, yet even that is an illusion: If you typically go out for such food at lunchtime, packing a lunch at home is even faster. I recommend nutritious snacks like carrots, fruit slices, or a yogurt cup that you take with you each day. And even at dinner, research from UCLA has demonstrated that if you have the right ingredients in your pantry and fridge, preparing a meal takes only about 10 minutes more than making a trip to buy fast food, costs less, and is much better for you.
If forgoing burgers and fries would leave you out in the cold with your friends at work, see if you can get a few co-workers to sign on to your new plan. You'll find that in a few weeks your taste preferences will change. After a couple of months, you'll actually be hungry for more healthful food.