You’ve heard of the “Freshman 15”…but could there be such a thing as the “Frosty 15”? It’s not a far-fetched proposition, based on a recent study led by researchers at University of Liverpool.

It’s no secret that cold weather turns many people into couch potatoes, so researchers wanted to investigate how inactivity affects the body. Most research analyzing the physiological effects of inactivity is based on space flight or bed rest. However, this study, which was presented at the Future Physiology 2019 conference in Liverpool, looked at healthy adults of different ages…and the results were eye-opening.

Study details: For this research, 26 younger participants (in their 20s and 30s) and 21 older participants (in their 50s and 60s) all performed about the same amount of moderate physical activity—more than 10,000 steps per day but no vigorous exercise. The participants were then asked to reduce their daily step count to 1,500 for two weeks to mimic the drop in activity that often occurs during the holidays or when the weather turns bad or illness strikes.

The results: The younger and older groups both experienced losses in leg strength (5% and 8%, respectively) and gains in body fat (2.4% and 0.7%). The two groups also had losses in muscle size and bone mass.

Here’s the kicker: Because the older participants had more body fat and less muscle than the younger participants at the beginning of the study, the researchers theorize that these changes are likely to have a bigger impact on the health of the older group.

In two other important measures, the older adults fared much worse than the younger group. Cardiorespiratory fitness (the body’s ability to transport oxygen during sustained physical activity) declined twice as much (10%) in the older adults than in the younger group. In addition, mitochondrial function (a measure of the energy that runs the body’s cells) fell by 19% among the older adults versus about 4% in the younger groups.

 The greater declines that occurred in the older adults’ cardiorespiratory fitness and mitochondrial function were considered noteworthy by the researchers, who explained that these changes are commonly reported in people who are in poor physical health.

“If the gym is hard to get to, people should be encouraged to just meet 10,000 steps, as even this can guard against reductions in muscle and bone health, as well as maintain healthy levels of body fat,” explained study author Juliette Norman, a PhD student and researcher at University of Liverpool.

For smart ways to stay active this winter: When cold weather keeps you inside, you can move around the house to your favorite songs…or get steps while enjoying this video.

Or check out fitness expert Denise Austin’s winter weather exercise recommendations here.