Here goes the 2019 holiday season. For many folks this means family visitation, traveling — and inconsistency of exercise and healthy eating. What does this mean for the fitness you’ve been working so hard for? Will the body turn into the mashed potatoes and cinnamon rolls it’s been indulging on?

Thankfully, exercise science has some answers, and the situation is not nearly as dire as one might believe.

Someone who’s taken up part-time residence in the gym will likely boast some fitness to prove their dedication. When lifting heavy weights, the body adapts by strengthening the neuromuscular controls to the muscles for a stronger connection and coordination to the movement. Lifting a moderate weight for a lot of reps builds muscle fiber size. A long endurance session builds the muscle’s engine of mitochondria. The lungs breathe efficiently. The heart pumps harder into more robust vascularity surrounding the muscles used. Insulin sensitivity (the mechanism which stores carbs as fat or uses them for fuel) is optimized to keep the body energized and lean.

Now it’s the holiday season. Friends, family, and people looking for free room and board show up, demanding our attention. Gym time is sacrificed to listening to Uncle John’s opinion on politics. Days go by, and they’ve become a prisoner to the entertaining and holiday banter, missing the gym. What happens next?

Over the course of a week, you’ll lose little to nothing. Holidays, however, cover four weeks or more. After four weeks of no training, cycling subjects saw a max decrease of 20 percent. Endurance time to exhaustion was reduced by 25 percent. In weight-training subjects, six percent of muscle mass was lost in three weeks. In seven weeks, the entire gains of a strength training program which was seven weeks in duration was diminished. Insulin sensitivity begins to reduce around 72 hours after the last exercise session.

This may sound extreme, but the body will resiliently hold onto the base levels of fitness for a long time — up to 12 weeks depending on the circumstance.

In subjects who were regular exercisers, one study did one set of a muscle group at 50 percent intensity. The subjects held onto their strength and muscle size. For endurance trainees, a reduction in 60 percent of training volume (total amount) and 30 percent of training frequency led to much slower decay. So, a few short runs and a single weight-lifting session — or even body-weight exercises ­—will suffice per week to maintain. Once you return to normal exercise, you’ll rebound much faster than the timeframe required to get the initial fitness.

If you are more fit, or have been training longer, you’ll lose fitness more slowly. A young person will have a slower decline than an older person. In the upper echelon of fitness, the top level of human performance is first to go. Base aerobic fitness, muscular strength, and flexibility takes a long time to go away. It’s the top percentage points which are what many competitive athletes are struggling for.

This holiday season, don’t give up if conditions aren’t ideal for workouts. Don’t stress the small stuff; enjoy time with family. A single weight-training session performed once per week can be done to maintain fitness. A few shorter runs per week will get the job done for endurance. Don’t worry once January comes, join everyone who didn’t exercise at all in the last year and set a good example in returning to the gym.