Frodo, watch my lips:
Roughage is not there to be digested it is there to fill the dog.  If they use something tasty like corn all to the good.

Whilst I am sure there are some rubbish lite foods out there, there are also some very good ones.
For example, Naturediet do a 'lite' version, it has chicken, lamb, tripe, carrots, seaweed and crushed bone, the same as the full calorie versions, but only provides 90 kcal/100 g  against about 125 kcal/100g in the 'normal' foods.
There is no corn or other rubbish, I would certainly try something like that in your situation to see if it is effective.

I tried the lite naturediet and it made absolutely no difference at all.  I think it just a case of different horses for different courses.  What will work for one wont necessarily work every dog.  I used the Pro Plan Lite and it worked a treat for mine dog and he lost the weight steadily and he also loved the food and didnt scrounge.

Everybody complains that extra cereal is just added to the lite diets, but isnt this surely what we do when we diet - we add more roughage to our diet.  I dont see what the big complaint is.  Both of my dogs are now on the Pro Plan chicken and rice and look the best they have for ages.  Their poos are fine, healthy looking and not loads of it despite what people say.  I tried Burns and the like but the poo was coming out worringly like solid bricks - surely that has got to cause some discomfort to a dog whilst going?  And the eldest just didnt enjoy his food. 

I'm glad you can understand it, dvnbiker, but then its not rocket science so I'm not sure why others can't :)
I feel exactly the same way as you about the rock hard poos I don't know why others treasure them :D and they certainly cause discomfort, when my Dandie started whining while passing them we ditched the bag and when back to feeding nothing with less than 3% roughage and never looked back ;).