Jennifer Chemel shares how she helped her dog Lucy slim down from 26 lbs. to 14 lbs.

Meet the Chihuahua Mix Who Went From Barely Walking to Running 5Ks After Dropping 12 Lbs.

When Jennifer Chemel spotted Lucy, a Chihuahua mix, at the Animal Welfare League of Arlington, Va., the pair had an instant bond.

Weighing 26 lbs., Lucy had social anxiety, and the shelter often fed her treats to ease her fears and make her more comfortable.

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“She was so sweet and friendly with me, and she loved snuggling with me in the visitation room,” Chemel, a government analyst, tells PEOPLE for the 2019 Half Their Size issue. “I felt so bad that everyone else had passed over adopting her. I knew that adopting Lucy would be a great way for me to have a friendly face waiting for me when I got home at the end of the day, and I wanted to help her get healthy again.”

The shelter had already enrolled Lucy in a pup weight-loss challenge and she appeared on The Pet Show with Dr. Katy, where a local vet offered advice on maintaining a 300-calorie-a-day diet. But Chemel made it her mission to help her newly-adopted companion slim down.

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Along with feeding Lucy portion-controlled bowls of dog food and religiously reading every label on treats or snacks to check their calorie counts, Chemel took Lucy to a local dog gym, where she was able to supplement her new diet with exercise on dog treadmills. She also created an Instagram account (@juicylucydog) for the pooch which chronicled her weight loss journey.

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But weight loss didn’t come easy for Lucy, now 6, who took more than a year to hit her goal.

“Dogs don’t have control over their diet like humans,” Chemel says. “She’s going to eat whatever is put in front of her.”

For more people and pets who have lost half their size, pick up this week’s issue of PEOPLE, on newsstands now.

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These days though, Lucy has a new lease on life.

“When I first adopted her, she didn’t ever want go for walks,” Chemel says. “Now we’ve done 5Ks together.”

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At her smallest Lucy weighed 13 lbs., but Chemel says the vet insists she’s healthiest at her current weight of 14 lbs.

Chemel says she still makes sure that Lucy sticks to her 300-calorie-a-day diet, but says she is less strict when it comes to cheat days. Chemel often gives Lucy larger treats to ease her social anxiety if she has a lot of guests over, and she always gets to indulge in one of her favorite snacks, a dog-friendly pumpkin ice cream or a tasty treat from a local dog bakery, on her adoption anniversary.

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“She just seems happier,” Chemel says. “Diet and exercise really work. Now that she’s lost the weight, she’s more comfortable and much more active. She’s able to run around and jump and just be a dog.”