If one of your main goals is losing weight, then aside from getting into the habit of exercising on a regular basis, monitoring what you eat is one area you must take into consideration. Even if you workout five days a week, unless you monitor what you put in your mouth, it's possible you could still gain weight.
Think of it this way, if a person were to eat a fast food "unhealthy" type meal three times a day that contained over 1,800 calories per serving with ridiculous amounts of fat, cholesterol, sodium, and sugar, that person would be consuming over 5,400 calories a day! When the general daily recommended caloric amount averages about 2,000, you can imagine that even exercising will do little to stop the increase in weight that is bound to happen.
However, with a little preparation and a certain amount of willpower, it's possible to get your food choices to become more appropriate. Even though every meal of the day (in addition to your snacks) need to be monitored and dealt with in a healthy manner, let's focus on building your arsenal of healthy recipes. Mainly because if you plan accordingly, you could cook/prepare enough so you have leftovers to pack yourself a healthy lunch to take with you to work the following day.
Getting in this habit will help prevent the need to ever have to go out during your lunch break to pick up some fast food or any other unhealthy option that's out there
One side note, when your priority is losing weight, it's imperative that you rid your kitchen of choices that are not going to be conducive to a healthy lifestyle. Unless you are willing to actually make a change in what you eat, not much will change in regards to your weight. If you don't have the ice cream, chips, cookies, soda, crackers, muffins, donuts, at hand in your kitchen, you will not be able to eat them on a random whim and you will be able to opt for something that is more healthy and beneficial for your body.