As a non banded Christian, I figure I'll add my own thoughts to the melting pot.
q. Is it a sin to perform WLS?
a. God knows. I sure don't.
There's strong argument that being so out of control is clearly sinful. Eating to the point of harming yourself is equally as sinful as drinking, smoking and a whole list of similar weaknesses.
Fortunately, God seems to understand that we're weak and easily beguiled as we've been making the same mistake since Eve grabbed the apple.
I think its entirely desirable to achieve the weightloss naturally, but what if its just not possible? What if you've tried and fallen back into harming yourself, time and time again?
WLS is the ultimate mark of determination and desperation to change your ways. God can be seen as the creator of all inspiration and therefor, the lap band could be seen to come from Him to resolve a very difficult problem to overcome.
When my wife decided that this was her last ditch hope and wanted to go for it, all the parts fell into place. The money showed up, the pre-op stuff flew by and before we knew it, she was banded.
Do I think her a sinner for needing WLS? No more than I think myself a sinner for needing to change my own diet to lose weight.
To summarize my view:
We are inately sinful. All we can do is try and be all that God would have us be.
I personnally would rather have WLS than continue to commit the sin of gluttony.
And here's a side note on my personal testimony for WLS.
To give you some background on myself, I've struggled with weight since birth, and I haven't struggled hard enough.
I am now also losing weight, thanks to the lapband that is installed in my wife. I doubt I could easily have done it without it (I haven't achieved permanent weight loss yet).
As for why I am losing weight, its simple. I'm legally blind and I have no means ot transportation other than my wife. As she is now banded, junk food has evaporated from my world. I can't get it, I can't order it, and so, thank God, I am protected from it.
So, if WLS is a sin, I thank God for using that sin to help me.
There is a bottom line here though, we can all question and guess, but only one person has the final ruling on what is or isn't a sin.
Pray on it, and God bless you all.