Kathy Riegelmann is different from most other fitness instructors: after teaching a boot camp class at 6:30 a.m., she heads to her bakery, where she bakes and frosts hundreds of cupcakes, cookies and other treats.

Riegelmann, who has taught fitness classes at Payne Whitney Gymnasium for 25 years, is also the owner of Katalina’s Bakery, which opened Friday morning at 74 Whitney Ave. The bakery offers a variety of cookies, brownies and whoopee pies, as well as over 13 different types of cupcakes, including vegan and healthy alternatives.

“[Katalina’s Bakery] has been a dream of mine for the past five years,” she said. “Cupcakes and cookies bring smile to peoples’ faces, young and old —it’s instant gratification.”

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This is Riegelmann’s second venture into the food industry — she was the original owner of New Haven coffeehouse Koffee?on Audubon Streetfrom 1993 to 1999.

Riegelmann said balancing her passions for fitness and sweets requires moderation, and “it’s all about portion control.”

James O’Leary, a faculty member atthe Yale School of Musicwhoregularly attends Riegelmann’s classes,said Riegelmannsometimes brings in cupcakes as a reward for participants in her class after a hard workout.

Riegelmann said business at the bakery has been promising so far, and that even Mayor John DeStefano Jr. came in and bought six cupcakes earlier this week.

Bennie Mayes, a histologist at the Yale School of Medicine, first noticed the bakery last Friday while riding his bike down Whitney Avenue — the whoopee pies in the window caught his eye, he said, and did not disappoint. He is already a repeat customer, having mademultiple trips to Katalina’s since then.

“The Yale Cupcake” competition, sponsored by the Yale Event Management Association, took place on Sunday afternoon and drew around 100 Yalies to the bakery. At the event, they sampled and voted on different cupcakes created from recipes submitted by members of the Yale community. Paulina Haduong ’13 and Yale staff member Gloria Hodu submitted the winning recipes, and their cupcakes, “The Yale Bulldog” and “The Eli,” respectively, are now fixtures on the menu at Katalina’s.

“The cupcakes were really good, and I liked the modern interior [of the bakery],” said Julie Cheng ’15, who attended the event. She added that she will return to the bakery, even though she finds it “a bit far away.”

Riegelmann said she plans to offer gluten-free baked goods as soon as she can find a supplier of bulk gluten-free flour.

Claire Criscuolo, owner of Claire’s Corner Copia on Chapel Street, famous for its cakes, cupcakes and gluten-free treats, said she is not worried about business competition from Katalina’s Bakery.

“There is at least one business selling coffee and deserts on every block downtown,” she said. “We’ve been here for 36 years, and we will continue to do our best to serve the community.”

Cupcakes at Katalina’s Bakery cost $2.25 each.