Truth

My son had DS on 10/24/08. He has lost over 300 pnds in a year and 6months. Is there anyone out their which has had the same surgery and lost this much weight in such a short period of time?

I know that Brock has lost a lot of weight as well as many others.  Stick around and you will find many people who have been this successful

Unfortunatly I am not agreeing that this as a successful surgery. My son is suffering! Suffering from severe muscle loss, tissue loss, malabsorbtion ......etc. I want my old son back!

I'm sorry that your son is not doing well.

What does his bloodwork look like?
Is he taking his vitamins?
Is he being compliant with getting protein?
Is he working with his doctor on the issues he's having?

Is he supplementing with protein shakes and taking all the required vitamins?  Who is his surgeon?  What does he have to say about the loss?  There are enzymes that can help him absorb more.

Enzymes?

Yes, I believe it's called Creon.

Again, what does his surgeon say?  Is he supplementing?  Getting enough protein?

To be fair, I think he was also suffering being 300+ pounds overweight.
All weight loss carries a degree of muscle and tissue loss as well as fat loss but one can try and compensate for it by eating large quantities of protein, taking all the vitamins and supplements as needed, weight lifting and constantly monitoring labs to make sure everything is high normal.

It does require a bit of diligence and work.

I am sorry your son is suffering but hopefully whatever is going on can be corrected.

As far as what is normal loss... Not that many have over 300 pounds to lose but an average trend seems to be around 100 pounds at the 6 month mark and then the rest over the next 6 months to year.

I too am wondering where this is going and what truth you seek. Speaking of, what tissues is he losing?!
It would probably be helpful for your son to seek help if he is malnourished from the medical profession that gave him the DS. 
Can you give specifics on what he his food/protein intake is as well as exactly how much and what supplements he is taking daily? There is a wealth of experience on these boards on how to take care of our bodies after choosing to have a Duodenal Switch.
You want your old son back, does he?

 Your "truth" needs to come from your son's surgeon.  No matter how much weight one has to lose, being monitored for vitamin deficiencies and protein malnutrition is a full time job for the post-op DS patient.  Are you in contact with his doctor?