The American Society for Metabolic and Bariatric Surgery (ASMBS) reports that 100,000 weight loss surgeries are performed each year in the United States, with approximately 300,000 Americans on the waiting list to have one. To shed more light on this topic, here are 10 facts you probably didn’t know about weight loss surgery. These eye-opening facts could help you or someone you love make an informed decision about whether or not to have surgery as part of their treatment plan.

How it works

People who are more than 100 pounds over their recommended weight may be candidates for weight-loss surgery. Through a series of small incisions, your surgeon creates a stoma, or opening in your stomach. The size and shape of your stoma will depend on how much you need to lose.

Who needs it?

Weight-loss surgery is an option for those who have obesity, a medical condition that’s caused by carrying too much body fat. But it’s not for everyone; doctors only recommend bariatric surgery to patients with a BMI of 40 or more and if other methods of weight loss (dieting and exercising) haven’t worked in previous years.

Safe during pregnancy

If you’re pregnant and considering weight loss surgery, know that it is considered safe during pregnancy. In fact, numerous studies have found that pregnant women who undergo bariatric surgery experience a lower rate of preeclampsia and gestational diabetes than women who don’t undergo weight loss surgery.

Cost effective

When you consider all of the factors, weight-loss surgery is actually a very cost-effective option. According to a study in Health Affairs, medical costs for those who had weight loss surgery were on average 30 percent lower than they were before they had surgery. Because an obese person may also suffer from other health conditions (including hypertension and diabetes) that can lead to even higher medical bills down the road, losing weight can translate into significant savings in many cases.

Do you have to be obese?

For those who are morbidly obese or have a BMI over 40, weight loss surgery is an increasingly popular option. But what if you aren’t morbidly obese? Most insurance companies and employers still won’t cover weight loss surgery unless your BMI is above a certain number—even if you are unhealthy in other ways.

Complications

In some cases, weight loss surgery can be more dangerous than beneficial. Between 1 and 10 percent of people who undergo bariatric surgery end up dying from it—and that’s not including all of those who suffer serious complications in the days and weeks after going under-the-knife. Other risks include a greater chance of heart problems, hypoventilation (the body can’t take in enough oxygen), organ failure, and internal bleeding.

What’s involved in recovery?

For most patients, weight loss surgery is a safe and effective procedure for losing weight and maintaining a healthy lifestyle. However, because it involves major surgery, there are some risks associated with undergoing gastric bypass or lap band surgery. In fact, some studies suggest that up to half of patients who undergo gastric bypass will have at least one complication after their operation. With that said, many studies also suggest that most complications are minor and can be treated successfully.

Risks are real but rare

About 1 percent of people who have weight-loss surgery die during or shortly after their procedure, according to a 2013 study in The New England Journal of Medicine. But that number accounts for all types of surgeries and procedures, not just gastric bypasses and sleeve gastrectomies.

How long does it take to see results?

Although your weight may not change instantly, you should see results fairly quickly after surgery. Most patients lose around 50 percent of their excess weight by six months and can lose 90 percent of their excess weight within five years. Keep in mind that these are averages and some patients will see a quicker or slower rate of progress than others.

And the best part…

Most people lose weight rapidly in the early stages of surgery, but over time, many gain some of that weight back. It’s important to remember that just because you have had gastric bypass surgery doesn’t mean you should throw out all your old habits. No matter what method of weight loss you choose, you have to incorporate healthy eating and regular exercise in order to maintain your results.