Overweight Dachsund/Cocker mix

Question
I have a precious dachsund/cocker mix that we rescued four years ago.  We believe him to be about 5 years old.  He is the sweetest, calmest, LAZIEST dog I've ever seen.  He's like a cat.  He sleeps all day and night.  I take him on walks pretty much every day, and a couple times a week we go to a park where he can run because we don't have a yard.

I feed him a reduced calorie very high end (expensive and vet recommended) food, twice a day, about a half cup each meal.  In spite of all this, he is STILL about 8-10 lbs. too heavy.  

I used to give him 3/4 of a cup of food each meal, but since I can't seem to get any weight off of him, I had reduced it to a half cup.

I know that in people, we can slow down our metabolisms by not eating enough.  I got to wondering if maybe I'm not feeding him enough!  I am worried about him.  He's had back problems in the past, and he's too sweet to die young.  I want him to lose weight, and while he's not gaining any, I just feel at my wit's end about how to get it off of him.

I should add that he rarely gets treats (one once or twice a week, also very low calorie high quality ones) and is NEVER fed people food (other than the rare occasion when I'll give him half a teaspoon of peanut butter). AND that he is STARVING ALL THE TIME.  He LIVES to eat.

Someone suggested supplementing his food with green beans and brown rice.  Low calorie fillers.  Is this healthy?  

I appreciate any assistance you can offer.

Thank you!

Answer
Sounds like you are making the right decisions food wise. The only thing I would suggest is to walk him more often. You may also take him to your vet and get him checked to make sure he isn't diabetic. It takes a long time to get weight off of an overweight animal (unless of course someone is starving them). Increase his activity and it will help. Also their metabolism is very different than ours so no you are not likely slowing it down by not feeding him more. Also is he on any medications? Some medications (prednisone, prednilosone, depo medrol, allergy injections or allergy pills, etc...) will cause weight gain. If he is on these medication there isn't much you can do to make him loose weight while he is on these meds. Hope this helps and good luck.