But the good news is that six months of healthy eating and exercise for your pooch or kitty can make a big difference: Just look at these before-and-after photos from the Pet Fit Club, a program run by the PDSA, a British vet charity. It put 17 pets on a diet and exercise program supervised by vets and nurses. The dogs, cats, and first-ever rabbit lost a total of 189.5 pounds and all got a, um, new leash on life.

Pictured above is the winning pet, a Cavalier King Charles Spaniel named Jack, who at 45 pounds was so fat he could barely walk or lie down comfortably (see his before photos here). After six months on a strict diet and regular walks and exercise, he’s a slimmer and healthier 31 pounds, with the new nickname “Jumping Jack Flash” displacing his old “Jumbo Jack” moniker.

“The difference in Jack is phenomenal—people actually think he’s a different dog,” his owner Rose Welch said of the transformation. “He was so sad before when he couldn’t join in and play with our other dogs, but now he’s so happy and lively.”

If you’re concerned about your pet’s physique, ask your vet about his ideal weight—and a healthy way to help him get there, including eliminating table scraps, sticking to proper pet-food portions, and getting lots of daily exercise.

For more fantastic pet makeovers, check out the success stories of fat cat Billie, chubby bunny Bobby, obsese border collie Merlin, and more.

Photo Credit: PDSA