You start with where you are today and with what you've got. Right now, you say you'd be embarrassed to take a Zumba Class, but know this, I take them and there are MANY different sizes and shapes.. don't let that t.v. commercial scare you. MOST are not in that good of shape, those people are hired dancers with a couple REAL people thrown in.. Otherwise, in those classes, you dance at YOUR pace.. but for now, how about you just go for a walk each day... start out slowly... set a goal and then add to it each day or whenever you do it..
Additionally, DO keep a good journal.. I thought I ate decently as well, but that was the problem, decent food or not, I was ALWAYS eating something... Use stairs in lieu of the escalator.... park farther away from a destination.. Buy a pedometer.. this way you can truly measure how much you are actually moving each day.. you'll find the steps add up..
Lastly, do as I do... write down specific REASONABLE goals.. e.g. this month I want to lose 5 lbs.... (don't focus on ALL 80) that is too daunting.. focus on what you can do in the immediate moment .. this way, you don't over think the weight loss and become stressed out.... vs if you think, omg. I have 80lbs to lose... that just feels like a lot.. start slow... also... when writing your goals.. consider what it is you will have to do to lose 5lbs a month... for me, it's exercise min 4 days a week and keep a food journal.... Don't go into this blindly.. by writing this all down, you can begin to see your progress and where you might need to tighten up..
lastly.... try and track your monthly cycle.. I think you might find like many women, the week before your period is the most difficult... CRAVINGS..... and lower energy.. it's during this time that you will need to have a plan of success in place.. otherwise, it's too easy to give into that specific time of the month... this might mean pre-making snacks.. this way, you eat every few hours and your blood sugar isn't allowed to get so low that you end up binging (like so many of us do) I think the more you PREPARE for success, the more you will succeed... :)
I wish you all the best