Ha! you sound like me -- I can wipe out a week's worth of workouts with one visit to the cookie cabinet! wonder why I even bother sometimes. If I'd only practice what I preach. But while I'm preaching and have some computer time to myself, let me blab on and on about the importance of the exercise part of weight loss, and why you need to do it while you diet.

Basically, when it comes to losing fat, one just doesn't work as well without the other. Why? When you diet, i.e., reduce your calorie intake, your body will, at first, begin to lose fat. Unfortunately, it will also lose muscle and bone mass which are an important part of your body's composition. As we age (especially for us women over 40), our bodies begin to steadily lose muscle and bone mass, which in turn, is why our metabolisms slow down. You need muscle mass to keep your metabolism up.
You may have heard this before, but the human body is very adaptable. It's built for survival. Take the Haitian earthquake survivor who the media swears was blessed by an act of God because he survived six whole days on beer and cookies (apparently, they were not aware that I, myself, survived my entire 20's on the same such diet). We are the original hybrid vehicles - whatever fuel you provide in whatever amounts, your body will learn to survive on. So when you reduce the amount of calories you consume, eventually, your body will adapt. And your metabolism slows down. And you know what happens next. When you do go back to eating like a normal person, as is inevitable, you gain the weight back . . . and more . . . because now your body has learned to live on less. So basically, the reward you get for weeks/months of starving yourself into a smaller dress size is enduring even greaters levels of starvation in order to stay in it. Yikes!
This is why you must exercise. And more specifically, do some kind of strength/resistence training. I'm not talking Miss Olympia or Arnold Shwar . . (however you spell it) workouts, but something that's going to help build and retain muscle. Cardio activities are good. They're good for your heart and circulation, and they burn calories. But strength training is even better. Squats, lunges, pushups, pull-ups, benching your 40 lb baby . . . all these things will help build muscle. The reason this is so effective is this: while you are working your muscles, you're burning calories. Then even AFTER your done (up to 48 hours afterwards), you're still burning calories while the muscle recovers! (yes, even while you're sitting on the couch). And here's the bonus feature: since muscle (much unlike fat) is an active tissue on your body, you burn more calories overall just having it - meaning it raises your resting metabolism. It's a cumulative effect. And it works well for those of us who prefer to EAT. So I think the message I'm trying to say is this. Diet by eating properly with fiber and protein rich foods while watching the sweets and other junk, AND off-set any metabolism-sabotaging calorie cutting with some good ol' sweat equity.
Oh, and last but not least - like I mentioned before, protein helps build and repair muscles so, Michelle, this may be a good opportunity to plug your Nutrilite website :)