Mia is going on a diet

Hi :-)
Mia has been gaining a lot of weight lately, a couple months ago I switched them from webbox sausages to chappie as Rizla wasn't eating it anymore.
Now Mia has gained a lot of weight and I'm thinking of putting just her back on the webbox sausages and walking her for a bit longer to shift the weight.
I was wondering if anyone has any other suggests to help shift the weight?

Hi Chez, how much exercise does mia get? You could probably cut down the food a little and up the exercise. Is it wet or dry food? I'm not familiar with Webbox?

I walk her every night for 20+ minutes after I finish work and longer on a weekend, I try to walk her on a morning before work but depends on time and weather really.
I feed her chappie and a handful of dry biscuit.. would it be best to just cut the food down bit by bit instead of changing it do you think? I'm in two minds about it..
Webbox was recommended to me for stopping dogs getting fatty and is quite good, Its pretty much a dog sausage (smelly one though)

I actually just did a lot of research on the Webbox sausage (chub roll) on my lunch break and found a lot of dog owners don't like them for certain reasons. I've decided I will avoid it, large number of people can't be wrong..
Definitely going to cut down how much food she gets and see how she gets on.
I'm also starting jogging so will take her on the jogs with me

Would you be able to change to one of the recommended foods from the list below ? Would also add James Wellbeloved and Wainwrights to the list:

http://staffy-bull-terrier.com/dry_food

This is a good site for comparing foods, definitely up the exercise   

http://www.whichdogfood.co.uk/