But the preliminary results of a small new study suggest that if you are going to overeat, there’s something you can do to protect against those negative effects: Exercise. And if you already work out on a regular basis, all you have to do is keep up with your normal routine.
This isn’t a total surprise, of course. It’s already known that as little as one week of overindulging can impair glycemic control and insulin sensitivity—processes that help the body process calories and keep blood sugar stable. (In fact, carb-heavy holiday meals can be downright dangerous for people with diabetes, for this reason.) And exercise has been shown to protect against some of these harmful effects.
But not much is known on how exercise can influence the body’s tendency to store excess calories during an overeating binge, or the structure and function of fat tissue itself. Its effect on inflammation—a response that's also triggered during overeating—is also not well understood.
So researchers at the University of Michigan wanted to see if a week of overindulging would have the same effects on regular exercisers as it does on people who aren’t physically active. To do so, they recruited a small sample of lean, healthy adults, some of whom got at least 150 minutes (and at least six days) of aerobic exercise per week and some who got much less.
The participants were tasked with eating 30 percent more calories than normal for seven days in a row, while continuing with their normal workout routines. (For someone who normally consumes 2,000 a day, that’s an extra 600 calories.) Before and after the experimental week, they provided samples of blood and abdominal-fat tissue.
The researchers presented their first results, on four participants in the exercise group, earlier this month at a conference sponsored by the American Physiological Society and the American College of Sports Medicine.
They found that, for these patients, a week of gluttony did not affect glucose tolerance. This finding matched those of previous studies on overeating and exercise.
But for the first time, the researchers also showed that overindulging also had no effect on markers of inflammation in volunteers blood or tissue samples. The researchers also found no change in lipolysis, a chemical process by which the body breaks down fast.
Lead author Alison Ludzki, a graduate student at the University of Michigan, says that the early results are not enough to determine any definite effects, of either overeating or exercise. Her team is in the process of recruiting and studying more participants, and hopes to have more complete data soon.
But she says that so far, they are seeing some trends to suggest metabolic differences between the groups of exercisers and non-exercisers. And that would make sense, she says, based on what’s already known about exercising and overeating.
“I think we can say that the big-picture advice here is that overeating, even for a short time, can signal some changes in the body—not just in fat, but in whole-body health,” she says. “And exercise definitely has some protective effects, especially when it comes to insulin sensitivity.”
Ludzki points out that the study participants didn’t have to do anything above and beyond their normal exercise routine to reap these protective benefits. “It was important to us that the study design was realistic and could reflect the average person who exercises regularly—not necessarily a high-level athlete.”
Laila Tabatabai, M.D., an endocrinologist and assistant professor of clinical medicine at Weill Cornell Medical College, says that the findings presented at the conference—although too preliminary to inform any real conclusions—imply two important points.
“One, exercise is protective against the harmful effects of consuming excess calories,” says Tabatabai, who was not involved in the research, “and two, the adverse effects of overeating are measurable after just seven days of excess caloric intake.”
She does note, however, that lean and active adults may be better equipped to handle overeating in general—regardless of whether they exercise during their binge or not.
Overall, she says the study is encouraging. “It emphasizes what we already know—that exercise is protective against inflammation and glucose intolerance,” she says. “The new and interesting finding is that perhaps exercising could help offset brief periods of overeating, such as during the holiday season.”
Ludzki agrees. “I would definitely suggest staying active,” she says, “especially if you’re going to be indulging in Thanksgiving treats over the next few weeks.”