I think 1 cup is quite a bit for a 25 lb corgi. Franklin averages around 29-30 and I feed him 3/4 cup a day and he is VERY active. May be worth cutting down his food a bit and seeing how that goes. I had to cut Franklin's back significantly about 6-8 months ago because he went from a dog I couldn't keep weight on to a do who gained 6 pounds in 2 months. He's doing great on 3/4 cup, if you feel bad you can add some green beans or carrots or peas to his food so he thinks he's getting more. I feed Franklin in interactive toys so he doesn't seem to notice (and it helps me to not actually SEE how little he eats! Lol). It's so hard to know how much to feed because the feeding guides on the bags are absolutely ridiculous! I just looked up the Authority and it says to feed 2 cups to a 21 pound dog! Anyway, try decreasing a bit and do bi-weekly weight checks and see if that helps. You can just drop in and weigh your pup at any vet or just pick him up and stand on the scale with him then weigh yourself and subtract. You really dont' know how successful you are or if he is losing too much unless you keep track of his weight regularly. Good luck!
I have my Romeo on Wellness Healthy Weight and it seems to be working out great! He likes it too!
When my dogs were chubby the vet said cut the food down 20%. Snickers will swear I am starving her to death. But her weight has stayed at a nice stable place for some time. I haven't measured her food in a measuring cup, just give her half a scoop AM and PM, one greenie, and one small milk bone a day. Plus some fruit and vegetables. She would inhale her food so she always gets fed in creative ways, interactive toys, muffin tins, sprinkles all over the kitchen, etc. The bowl I bought her is too big, which makes her servings look really small and she will testify that it is not enough food. But her waistline says otherwise. (I scoop the kibble into the dog bowl then carry it to the dog cupboard to pull out the toys) There are days that I can tell that she is genuinely hungry and I'll give her another half serving. ( I think if she had unlimited food she would eat until she burst) Snickers is 4 and weighs 22 lbs. She has recently taken up chewing on Nylabones and the Hartz treat and chew. Maybe Jasper would enjoy something to do when he is thinking about rummaging in the fridge out of boredom (like I do). Just like people, he will be better off losing weight slowly, 4 pounds is not so much that it will hurt his health if he doesn't lose it all right away. If he is messing with the trash, you need to seriously look at fixing the cupboard so he can't get to it. The trash bag/ can is a very dangerous place. If you haven't followed past discussions, all food bags need to have the bottom cut out of them to prevent suffocation.
I would try cutting him down to 3/4 cup a day and use green beans for filler to help him feel more full.