I am 5’8” about 220 pounds and a 42DD. If I were to go down to say 200pounds how much smaller would my band size go down. I figure I would go to a 40 which would make me a DDD!!!

I lost 60 pounds over 3 years, 250 to 190. At 250 I was a tight 44/46. At 190 I'm a comfortable 40. 38 in some bras but I'm not there yet. A little of that is muscle, as I'm actively trying to lose fat but add lean tissue. I'd say there's a good chance that you'll be a 40 at 200 pounds but it really does depend. We all lose weight differently. 

And now, because we all love unsolicited advice.

Please remember; There's a lot of really bad information out there from various fitness "gurus". Crash diets are generally not only bad for your health, but the weight usually comes back and brings along some friends. Same with specific food restrictions. That can really mess up your relationship with food and usually results in yoyoing. Slow and steady. Eat fewer calorie dense foods (fewer not none) and move more. Just being more active can help tremendously. 

Good luck Beth.

Thank you. Great advice. So around 20 pounds is a band size

How is the weight loss going Beth?

Erica,

Sound advice, wife just change what I eat, no white stuff lots salmon, vegetables, fruit, nuts, (not what your thinking).  Not so much what I eat as what I don’t eat.  Lost 58 pounds in 9 months.  Eat healthy and exercise and you’ll get to the size you should be.

Pooky