Nosy People

I started My Fitness Pal about 1 year ago, with the main intention on tracking nutrients, and I really only wanted to lose about 10 pounds. However, in the past 8 months, I have lost about 30 pounds, not only as a result of diet and exercise, but also some digestive health/food allergy-type problems I've been recently dealing with. I now am wanting to maintain weight (or really, I should probably even gain at least 5-10 lbs back, since I didn't intend, or need to, lose all the weight to begin with).

Lately, I've been dealing with people I barely know telling me how I'm too thin and telling me "girl you need a cheeseburger!". I know people are concerned, since I have lost weight pretty quickly, but these aren't people I feel comfortable disclosing my health problems with, and quite frankly, I find it rude and offensive when they make these comments. How can I politely let them know to mind their own business??!