I am in a wedding party how do I stop being the fat funny guy

There you go.  That should be all you need.

As far as drinking and being the life of the party, blahblahblah, tell them you're in training.  Simple as that.  When they ask you what you want to drink, say water. 

Steve

My husband's a recovering alcoholic and has many answers to the "where's your drink" one I can share with you.  Off the top of my head...

"I'm the designated driver".

"I'm on call tonight"- works only if they don't know your job. You can lie. Make sure you have an obligatory cell phone or pager they can see.  You can also say you're a lawyer in California- one DUI and poof! buh-bye, law license.

"My kids are here".  uh..... maybe not?   I use that one myself though. "I want to remember this night".

"There's a cop stationed down the road just waiting to pull over someone."

Now I'm reading them I realize they're not very good.   You can get one drink and nurse it as long as you can.  I have found it entertaining being sober and watching all the drunk people act, well--- drunk.  

Now that your wife is pregnant you can stop drinking with her

 Try not to worry about what people say. 

Start coming up with great comeback lines instead of taking them.  The drunk relative?  Call him "skinny drunk ugly asshole".  I'm not the brightest bulb out there, though.

You've taken the first step, you realize you have to change.  Things can only get better.  Good luck.

Given your family history, be a good idea to get a great physicial soon if you haven't already. 

Simple, when asked....tell the truth. If you actually are funny, you should be able to spin a lifestyle change into real good mateial. Hell the "I broke a chair...with my ass" line is pretty freaking good.

or maybe go to Lenny Bruce -like extremes

"Where's you drink fat boy?"

"I mush have left it with your mama....."

well maybe not

Seriously, though a wedding is a one-time event, and it's about the couple who are getting married. Unless you're being hired for entertanment other peoples' ideas about how you should behave are irrelevant. You're making a commitment to change your life. Some things will have to go (constant overindulgence) other things will stay (sense of humor).

It's only peer pressure if you let it be. You get to (have to) define your own life.

Congratulations on the little one.

Also works with tonic or club soda, depending on your drink of choice. A slice of lime in the glass also makes it look alcoholic.

I like the not drinking with your wife thing, but that hides what your are really doing.  Try being honest... my wife and I are having a healthy pregnancy.  I want to be healthy and here for my baby to give him/her the dad he/she deserves. Then, you can tell them you are getting into tris and see if they want to join you in all this fun! 

Good luck to you and congratulations!

You don't need to justify what you are drinking to your friends.  If someone asks "Where's your drink?"  say, "Right here." as you hold up your glass of coke, or water or whatever.  If you've already drunk the amount you decided on, you can just say, "I've already had my limit for tonight."  But I find the first response works the best. Mostly, it's feeling comfortable with your choices and not feeling like you have to explain yourself to anybody else.  Just drink what you want whether water or bourbon and don't feel like you have to explain it to anybody.

If you say things like "I'm not drinking tonight, cause I'm in training," well, that will challenge some people and they will feel like they need to get you to drink. 

First off, congratulations on your decision to train for a tri and on the pregnancy.

If people ask why you're not drinking, just tell the truth. If they're really your friends, they'll understand and be supportive. If they have a problem with it, the problem is theirs, not yours. Someone pressuring you to drink alcohol when you've stated you don't want to is seriously screwed up. Look at each new situation as an opportunity to learn how to get through those situations.

Triathlon is about overcoming obstacles. Keep your goal in mind and make the decision that you're going to do whatever it takes.