By CHRISTOPHER KAZARIAN

Those dreaded holiday pounds usually start arriving on people’s bodies during Thanksgiving week. And they often stay there through the new year when those same people make resolutions to shed that added, unwanted weight.

“On average people gain five pounds between Thanksgiving and Christmas,” said Amy Sellers, a certified fitness instructor at Uptown Body Cape Cod in Falmouth.

So how then to prevent this holiday weight gain in the first place? “My advice is to treat your workout like your Christmas party or luncheon and write it down,” Ms. Sellers said. “Make it a date that is an important date for you to keep.”

December, she said, is an ideal time to work out as classes are smaller and there is more personalized attention versus after “New Year’s when everybody is showing up” to the gym.

She suggested one way to remain motivated these next few weeks is by mixing up your workouts. Try yoga one day, Pilates the next and cardio the next. “That keeps it interesting and helps you get through the holidays,” she said. “Try something you have not tried before.”

Ms. Sellers, who has been in the fitness industry for over 30 years, currently leads classes for those over the age of 60. The focus is on functional exercises— movements people do every day of their life—and ways to do them safely and correctly. The goal is to improve one’s balance, strength and fitness level.

But the benefits go far beyond that. “Friendships are forged,” Ms. Sellers said. “It is also fun to work out with someone else, especially during the busy holiday season.”

Fun is the operative word behind two holiday-themed races on Cape Cod scheduled for Saturday, December 5: the 4th Annual Jingle Jog 5K and Kids Elf Run in Falmouth, and the 3rd Annual Santa Stampede in Orleans.

These short, relatively manageable races are followed by the annual Run and Dunk that takes place on New Year’s Day at Old Silver Beach.

Both the Jingle Jog and the Santa Stampede encourage participants to dress up in their most festive outfits, each offering awards for the best costume.

“More people dress up than not,” said Michael Kasparian, president of the Falmouth Chamber of Commerce, which organizes the Falmouth event.

Dressing up, whether you choose to Jingle Jog or participate in the Santa Stampede, is almost as mandatory as training for these fun December fitness events.

The Jingle Jog begins and ends at Bigelow Marine Park next to the Flying Bridge Restaurant on Scranton Avenue, taking runners on a 5K run that follows a portion of the Falmouth Road Race through Falmouth Heights. Adding to the family-friendly nature of the event is an Elf Run for those 12 and under.

The race concludes with a visit from Santa, who is escorted into Falmouth aboard the Patriot II Party Boat. “Being outside in the air, there is both an element of fun and athleticism in there,” Mr. Kasparian said.

That is also the underlying theme behind the Santa Stampede, which follows a scenic route through East Orleans, beginning and ending at The Barley Neck Inn on Beach Road. “Runners have told us they like the route because they are somewhat challenged, but it’s not unreasonable for walkers and novice runners,” said Noelle Pina, executive director of the Orleans Chamber of Commerce.

Similar to the Jingle Jog, there is a festiveness to the event with holiday songs played before, during and after the run by DJ Matty Dread of Provincetown’s WOMR.

“I would say most [runners] do something. Some are in Santa hats or have bells on their shoes or wear red and white long socks,” said Ms. Pina. “Some are in full costume. Last year we had a group of ladies dressed up as Christmas mermaids, which was really fun. We had a reindeer, elves and a Christmas tree. Of course, we’ve had Santas and Mrs. Clauses.”

The stampede is preceded by a Mini Claus Run for children who are 12 and under.

While these races provide residents an opportunity to kick off the season with a little exercise, the Run and Dunk serves as the perfect way to end the holidays by doing the same.

Although the event is capped with a New Year’s swim, participants can opt to only do the run, which includes two distances—a shorter, three-mile jaunt and a longer 5.7-mile one. Started by Dr. Gregory Parkinson of Falmouth over a decade ago as a fun way for his family and him to welcome the new year, the Run and Dunk has blossomed to the point that it is a fundraiser for a worthy cause, the Cape Cod Center for Women, so participants can get in a holiday work-out and feel good knowing they have helped someone in need by doing so.