How 'DC Cupcakes' Sisters Shed More Than 100 Pounds

— -- Katherine Berman and Sophie LaMontagne are not only sisters but also co-owners of the popular Washington, D.C.-based cupcake chain Georgetown Cupcake and stars of the reality-TV show "DC Cupcakes."

Now the pair can add another item to their list of things they share in common, substantial weight loss.

The two sisters shed more than 100 pounds together, all while being constantly tempted by sweets and treats in their roles as cupcake chefs.

The weight gain for Berman and LaMontagne began two years ago when a then-pregnant Berman put on 60 pounds.

"The weight came on so quickly and so fast for me," she told ABC News. "And my portions were a little bit out of control."

Berman's sister soon found herself getting heavier, too, putting on the pregnancy-sympathy weight.

"I was basically eating as much as Katherine, even though I was not eating for two," LaMontagne said. "You just naturally eat as much as they do. You're in the same surroundings and same situations and, before I knew it, I had gained 40 pounds."

Once Berman gave birth to her daughter, in March 2013, the sisters got to work on a weight-loss plan.

"We didn't want to diet," LaMontagne said. "That's not a word that's in our vocabulary as bakers."

Instead, LaMontagne and Berman focused on a simple exercise they could do anywhere, anytime.

"So we just started walking, and that's all we did," LaMontagne said. "We walked six miles a day, five days a week and we did it consistently.

While allowing themselves one cupcake per day and focusing on more sensible portions overall, the sisters lost a combined 100-plus pounds in nine months.

New York-based nutritionist Maya Feller says the "DC Cupcakes" sisters took the right path in focusing on both diet and exercise.

"It's really important to think about how one can balance their diet, and how that fits into their overall lifestyle," Feller told ABC News. "Exercise alone is not the only answer. Diet alone is not the only answer.

“There needs to be a real balance and marriage of the two," she said.

For Berman and LaMontagne, the sisters found out that great business partners also make great weight-loss partners.

"Having a friend or a sister or somebody that can work out with you is so key because you motivate each other," Berman said.