Previous research has shown that even a few days of consuming far more calories than you burn can damage your health.
The new study included 26 healthy young men who were asked to overeat and who either were inactive or exercised on a treadmill for 45 minutes a day. Daily calorie intake increased by 50 percent in the inactive group and by 75 percent in the exercise group. That meant they had the same net daily calorie surplus, said the researchers at the University of Bath, in England.
After just one week of overeating, all the participants had a significant decline in blood sugar control. Not only that, their fat cells activated genes that result in unhealthy changes to metabolism and that disrupt nutritional balance.
These negative effects, however, were much lower in those who were doing daily exercise, according to the study, which was published Dec. 15 in The Journal of Physiology.
"Our research demonstrates that a short period of overconsumption and reduced physical activity leads to very profound negative changes in a variety of physiological systems," study co-author Jean-Philippe Walhin said in a journal news release. "But a daily bout of exercise stops most of these negative changes from taking place."
And holidays often mean people are eating more and exercising less, another researcher said.
"If you are facing a period of overconsumption and inactivity, which is probably quite common around Christmastime, then our study shows that a daily bout of exercise will prevent many of the negative changes from taking place even though you are gaining weight," study senior author Dylan Thompson said in the news release.
"The effects are obvious, but the underlying causes will need further study to be determined," he said. "The findings are likely to apply to other groups, like older adults and women, and perhaps to lesser amounts of [exercise]."
The U.S. Centers for Disease Control and Prevention offers holiday health and safety tips.