Comments making me uncomfortable

Whether he's genuinely concerned or not isn't the issue. He's asking inappropriate questions. He has no right to ask such things. 

It doesn't matter how concerned he is; he's overstepping the bounds. 

I always talked openly about my surgery and found that people were very supportive.  One of the reasons I didn't keep it a secret is because I knew that people would notice my weight loss and would wonder about it.

Sounds like Troy is concerned about you.  Hopefully since you told him your weight loss was from diet and exercise, he will realize there is no need for concern.  Of course, he may now start asking questions like how much weight have you lost, what kind of diet are you feeling, etc.  Best thing to do is tell him thanks for your concern, but I really don't like discussing my weight loss.  It's tough to be in your position, but you really need to talk with him.  I wouldn't do a memo though, unless he continues after you've told him to back off.

Hope you can resolve the issue sooner rather than later.

So this is a weird situation.  On the one hand, I'm 100% honest about having had surgery.  On the other hand... it's really awkward when people start asking personal questions if you're not at that level with them.  (Just today I had a substitute yoga instructor I hadn't seen for a very long time and she started quizzing me about my weight loss IN FRONT OF THE CLASS.  ARGH.  Screw you, yoga instructor!!)  

I think that the best option here is to figure out how to diffuse the situation and get back to the friendly, casual greetings that don't acknowledge your body.  To do this, I'd probably work on making a list of really silly and completely implausible answers to give him about weight loss.  

"I only eat grapefruit.  It sucks, but at least I won't get scurvy."  
"I bathe in the blood of squirrels every night, it keeps my skin young too!"  
"The thigh master - 10 hours a day, I'm using it now under the desk actually."
"I wrestle tigers every weekend.  Want to see the scars?!"  

But that's just the kind of person I am.  Eventually an intelligent person would get the hint that this isn't a topic you care to talk about.  

I like to be flip, too, with people who won't take a hint.

I only eat food that doesn't taste good.

Purina Puppy Chow Diet.

I just visit food at the grocery store.

I like the Puppy Chow one :D

I have taught my 11 year old daughter this tactic. She was born with a cleft lip/palate and often gets questions about her scar. "I got attacked by a grizzly bear" is her favorite.

Tight attack is my go to for scars :D  I love your daughter's tactic!

Sorry to thread jack here -- but really?  WTF is wrong with people?  A cleft is something EVERY F-ing adult has seen and should have some understanding of -- WHY in the world are they asking questions about her scar?  Why would anyone do that to a little girl?

People are just remarkably ignorant.  

If her clever response didn't work, I am sure the real grizzly bear (mama) takes care of it for her.

I will never cease to be shocked at what jerks people can be.

Yeah, there are a lot of ******** are out there. I do take care of it. Thanks 

Is he overweight? He may be asking for himself. If he is not overweight, I wonder if he is asking for his spouse or a friend or family member. That doesn't make it okay for him to be persistent and continue behavior that makes you uncomfortable, but it would explain what his interest is.

Maybe something like this would work. Troy: Hey, how's the weight loss? Are you doing Cross Fit, Barbeque Challenge, or the Puppy Chow Plan?

You: I don't talk about my diet and health--it's only interesting to me. After all, it's like hearing about your great Aunt Minnie's hammertoe surgery. Booorrrring.

 Hey, have you seen Hamilton ? It was fantastic.