There is a science to losing weight, and it is simple: spend more calories than you take in. That is really all there is to it. Oh, it can get much more complicated, but it doesn't really need to.
I lost alot of weight, just thinking about that actual statement, and it worked really well. I think the biggest problem for most people is information, namely the fact that they don't understand just how many calories they need or how many calories they burn.
Exercise can be a great help both aerobic for burning calories on that day and anaerobic (Such as weight training) for increasing your metabolism (Which increases the amount of calories burner while not working, usually referred to as your Resting Metabolic Rate [RMR] or Base Metabolic Rate [BMR]).
The thing is exercise isn't actually required to lose weight, but without it your body just won't be shapely enough to be pleasing usually. Exercise though, tends to add to muscle so if one does exercise to lose weight a photograph may be a better way to keep track then a scale, where the number doesn't care weather it is muscle, bone, or fat that it is measuring.
What worked for me was a food plan and calorie log, along with light exercise. In my food plan everything was planned out by time and calories the week before and I just had to stick to my plan. And I did have to ratchet the amount of calories down over time even with my exercise. I started at about 2500 a day (Yes, I lost weight at that amount per day) and now I should be at around 1800 a day (even though this last week I have been on about 1300 a day, due to financial constraints).
You can use calculators online that can compute what your eventual weight would be based on calories per day. Assuming you have your RMR figured out correctly, these figures should get you in the ball park for the amount you should actually eventually be eating.
One word of caution about that, when you eventually figure out how many calories you need very few versus what you'd expect. That is rather normal, I have had to give up pretty much all fast food in order to have 4 meals a day. There is just not much on the fast food menu that can fit into a calorie budget, and leave enough left over a whole bunch more meals.