When it comes to exercise and diet for those that are just thinking about starting either, we always tell our clients that losing weight starts in the kitchen and is finished in the gym. Meaning before you start an exercise regime at least try to get your nutrition under control as well. I'm not talking about starving yourself either, I'm talking about making good food choices! For instance, eating so many vegetables that you are completely stuffed and therefore don't want junk food. There is no point in starving yourself, that only leads to overeating and binge eating.
Let me put it this way (all hypothetical of course):
Option one - you jump on the treadmill and run/walk for an half an hour (if you even have the time for that). In that half an hour you might burn 200 calories which is fantastic, but are you going to do that every single day of the week??? Uh no, no one has the time for that! And many times after doing such a thing you are famished and if you are not making smart food choices you could end up overeating and ruining all of that progress! So maybe you do this 3 times a week = 600 calories.
Option two - you start making wiser food choices, and are actually EATING and eating healthy (there is no point in there did I say starve or go hungry). You are eating the right things (vegetables, fruits as snacks, nutrient dense proteins, high quality fats, plenty of water), your body is running more smoothly, you probably have more energy (no processed food crap is going through your body), and that's without setting foot on the treadmill. Doing this you may cut out 200 calories in your diet a day - 1400 over the course of a week.
If you had to pick, take control of your diet first! You control when and what you eat, you don't always control if you have the time to workout. Ideally of course we want to do both and really make our bodies the efficient machines they can be and increase our exercise capacity.
So just so you know I'm not full of it, I'm a certified AFAA personal trainer, published scientific author, seen in Red Book Mag, Shape, She Knows and many more, contributing author for Natural News, The Active Times, Answers.com ... etc., operate AlwaysActiveAthletics[DOT]com and I have even set up an all inclusive workout/nutritional club for moms (and all females alike) that offers support, motivation, at-home fitness instruction, and accountability in one amazing package (you can easily find it a the main site)