Most of us know the occasional cheat meal is no big deal. It’s not like one night of overeating can undo months of dieting and working out. But what about a week of overeating? Or what if eating till your stomach hurts becomes a regular weekend habit? If your diet is clean all week, can overdoing it actually mess with your body?
The answer is yes, says Ilyse Schapiro, R.D., C.D.N.: “If you’re healthy, occasionally overeating won’t kill you. But regularly overeating, or overeating for an extended period—such as a week or more—may cause changes in health and body composition.”
Kind of scary, right? Here’s everything you need to know before going on that next burger bender—and how to indulge without throwing your health goals or physique progress off track.
1. Overeating can soften your six-pack
If you’re healthy, overeating on Thanksgiving or over a holiday weekend probably won’t fill out your washboard abs. But it really depends on how much you eat. Whether you overeat for one day or one week, your body will transform any extra calories into fat, says Leah Kaufman, R.D. “If you consume an excess of 3,500 calories, you’ll gain a pound of fat. If you consume 7,000 excess calories, you’ll gain two pounds of fat, and so on.”
2. Overeating nudges you closer to diabetes
The extra body fat that comes about as a result of overeating does more than just make your pants feel tight. It can also lead to insulin resistance, a precursor to diabetes that occurs when cells are unable to convert blood glucose into energy. And we’re not talking about months or years down the line, either. You can become insulin-resistant in a matter of days. In one Science Translational Medicine study, six healthy men ate 6,000 calories per day and stayed on bed rest for seven days. After just two days of extreme binge eating, all of the study participants had developed insulin resistance. Though the researchers hypothesized the men’s blood sugar issues would resolve after they returned to their regular diets and fitness routines, they argued that if the men were to continue to eat in excess, they would develop full-blown diabetes.
3. Overeating can mess with that “full” feeling
If overeating becomes your new normal and you start to gain weight, levels of your weight-regulating hormones may become altered. In one Nutrition and Diabetes study, researchers overfed mice and found that their intestines stopped producing uroguanylin, a hormone that helps send feelings of fullness to the brain. When the animals started to consume a healthy number of calories again, levels of uroguanylin increased. Experts hypothesize that the same thing happens to humans, as well.
“After a period of overeating, one’s perception of fullness may be altered,” explains Schapiro, who was not involved with the study. “After the body becomes accustomed to eating more calories, taking in fewer calories will confuse the body and make it think that it’s underfed, causing hunger to persist.”
To get back on track with feeling full after a normal serving of food, Schapiro suggests adding more fruits, vegetables, and whole grains back into your diet. “This will help offset the unhealthy food that has been consumed while still helping you meet caloric needs.”
4. You’ll feel exhausted
If you tend to binge on chips and ice cream when you watch TV after dinner, you don’t just need to worry about the extra calories. “Overeating, especially around bedtime, can negatively impact sleep,” says Kaufman. “When you overindulge, your body is working on overdrive to try and break down the food. But if your body is working when you’re trying to sleep, it’s not being signaled to shut down for the night.” This sets off a vicious cycle: When you don’t get a good night’s sleep, the hormones that regulate hunger become altered, which can increase hunger and trigger bouts of overeating, according to University of Washington findings.
5. Overeating stresses your cardiovascular system
After a large, fatty meal, the body is flooded with insulin, which makes it more difficult for the coronary arteries to relax, explains Schapiro. Eating and digesting large amounts of food also cause the release of the stress hormone norepinephrine, which increases heart rate and blood pressure, adds Kaufman. These natural reactions can trigger the formation of a clot that can block a blood vessel, triggering a heart attack or stroke. In fact, heart attack risk jumps four times in the two hours following a large meal—especially in people who already have heart disease, according to an American Heart Association study of nearly 2,000 participants.
But that doesn’t mean you can chow down without worry if you don’t have a history of heart disease, Kaufman cautions: “Although blood pressure will probably go down eventually, there are risks associated with a change in blood pressure brought on by heavy, fatty meals.” Schapiro echoes Kaufman’s sentiment, adding that, “overeating may not cause a heart attack if you’re healthy, but it but can trigger symptoms or start the process of a heart attack.”