How much weight would I lose if I purged my dinner every day? Eating healthy or semi healthy lunches and then purging my usually unhealthy or semi healthy dinner?
Basically none.
Your body already takes in the calories you're consuming as soon as you consume them. That means that you're just expelling whatever is in your stomach. Not the calories. You'll feel lighter, yes, but you will not be losing any weight. Purging and/or not eating at all is not a successful way to lose weight. In fact, it can often do the opposite and give you negative side effects. For instance, when you don't eat for a long while and then you finally do, you'll bloat and usually get gas due to your body working so hard to digest something it hasn't had in a while. Not only that, but when you're depriving your body of nutrients and food, it will just do whatever it can to hold on to your fat storages. Therefore, you might lose some weight but it will be muscle and organ weight. You'll still be flabby. And as stated, when you binge and purge, you're taking those calories in still. It doesn't matter if you throw it up. Your body still has those calories in it. When you're throwing your food up, the stomach acid can ruin your esophagus and your tooth enamal. It can also yellow your teeth and break blood vessels in your eyes. In my experience, most who binge and purge also become conditioned to the routine and will throw up after meals regardless of whether they want to or not. It can also, in severe bouts, cause major health problems as well.
I assume you want to lose weight quickly and that is why you want to do this. Losing weight quickly will just make your skin loose and flabby. The best way to lose weight, keep it off, and keep everything tight and "tidy" on your body, eat 5-6 small meals of about 250-350 calories each. You'll stay full, your body will never feel hungry enough to want to binge (and you'll make healthier decisions when it comes to eating because you will stay full and satisfied), and your metabolism will rev due to you keeping your body constantly working to use those calories through digestion. Pair that up with 4 days of cardio of about 45-60 minutes, and three days of 1 - 1 1/2 hours of strength training a week and you'll see major results. I lost 45 pounds in the span of 3 months (the course of a summer) and I've kept it off since, by doing this. And I went to school for dietetics so I give this advice with results for a living.