MEDIFAST PRODUCTS???
Um, I have to SERIOUSLY disagree with you here. You CAN indeed eat too much natural sugar having had an RNY and being violently ill is one little bit of proof in that pudding. Bananas made me dump from the start, as would anything else that was sweet. I can eat them now, but I'm over a year out as well.
Generally a person should strive for lower carb after an RNY for a couple of reasons: 1) You should get your sustinance from protein first because it will give your body most of what it will need while you are losing so quickly. You need protein more than carbs. 2) Sugars - even natural - make most people who have had an RNY dump. 3) Too many carbs can cause water retention and can stall loss.
I eat a lot of fruit now, but one should go at it slowly at first and see what their bodies can tolerate. Certainly you don't have to live without it, but you need to be cautious and gentle with yourself. No sense in knocking yourself out for 3 hours because you are eating something natural and normally good for you. We are altering our bodies here - we are going to have to modify how we do things. Consider it an allergy. Some people are allergic to peanuts. We tend to be allergic to sugars.
As for trying the watermelon - go ahead. Just go slowly and eat a little bit. If your heart starts racing after a very small serving, stop and wait before you try it again. Give it some time....
Dina