I have a standard schnauzer who from an early age was always a bit of a porker!
He doesn't eat a lot but he had an illness recently and the vet had to put him on steriods. I bought some scales and weighed him and he really is too heavy for a young chap. He is 18 months. I feed him a lite dried food diet and tuna as he won't eat anything else. I do give him the occasional treat but I dont feel I give him too many.

He seems to be getting bigger and the vet doesn't wasnt to give him anything to lose the weight because he may rely medication for the rest of his life.

Can anyone advise on anything herbal or anything at all that may help him get the weight off. I just want to give him a healthier and longer life.

I too have a big boy.  Dogs get fat because of what goes in their mouths.  Exercise will help but reducing his rations is the only way.  Use some of his food as treats instead of giving them as extra.  And take him on nice long walks til he's too tired to eat :)

Is he still on steroids? Are they permanent medication? Weight-gain is a known side-effect of steroids, unfortunately.

No he is not on sterods anymore. Infact he was only on them for a couple of weeks and that was last October. The vet did say thay take around a year to get out the system. But I just wanted to put him on a healthier diet in the meantime.