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Being fat sucks. I’m not judging; I’ve been overweight all my life. Obesity puts you at risk for high blood pressure, heart disease, stroke, and even some cancers.

Then of course there’s Type 2 diabetes. The mother of all obesity-related complications keeps your body from regulating the sugar it needs as fuel, and can lead to all kinds of health issues, like kidney damage, heart disease, and even limb amputation.

That could change, if pharmaceutical companies can convince doctors that a new-ish class of drugs can attack Type II diabetes and the fatness that begets it—without killing patients. Earlier this month, at the Endocrine Society’s annual conference in Boston, Danish pharma Novo Nordisk presented three years of data showing that their diabetes drug liraglutide helped obese and prediabetic patients lose weight without undue risk. Which is big, for a drug that’s been flagged for causing cancer.

In rats, that is. Liraglutide—or Saxenda, as it’s known commercially for weight-loss—carries a black box warning from the FDA for giving thyroid tumors to rodents. However, the specific tumor-causing cell biology is different enough in rats that many endocrinologists don’t consider it a significant risk to human patients.

Many, but not all. Weight loss drugs are historically pretty risky. Remember Fen-Phen? It was great at helping people get skinny—as long as those people were OK with developing chronic heart problems. Fen-Phen was pulled from the market in 1997, and its maker had to pay billions of dollars in legal fees.

Liraglutide, in Saxenda form, might be the best alternative since Fen-Phen—especially since it probably won’t kill you—but the old black box warning along with institutional skittishness related to weight-loss medication means Novo Nordisk wants to push extra hard to get doctors to believe the drug is safe.

Especially because it could mean billions in new prescriptions. Another form of liraglutide, called Victoza, is cleared for treating Type II diabetes, which affects 29 million Americans. As a therapeutic category, diabetes drug costs rank the highest per patient per year for traditional therapies, according to a 2015 drug trend report by Express Scripts. And if you’re on a diabetes drug, you’re on it for life. That’s a huge, reliable market. But more than three times as many Americans—100 million—are obese or overweight. I know what you’re thinking: Another pharmaceutical company figured out a way to exploit our desire for a quick weight-loss fix while making a pant load of money.

It's true, liraglutide fills a lot of Novo exec’s pants with a lot of money. In 2015, the drug made about 3.5 billion USD selling liraglutide1. In fact, liraglutide is the most profitable of a class of drugs known as GLP-1 agonists—lab-engineered compounds that mimic a naturally-occurring molecule that your body uses to regulate blood sugar.

Now, this new indication for the drug isn’t all about money-grubbing. Liraglutide has been FDA-approved since 2010, (the agency approved higher dose, weight-loss specific Saxenda in 2014), but “I don’t think we realized how good of a weight loss agent it was until fairly recently,” says Ken Fujioka, a doctor and diabetes researcher at the Scripps Clinic in La Jolla, California, who led the study—known as “SCALE”—Novo presented at the Boston conference.

Initially, weight loss was just a side effect observed in liraglutide research. But there are good reasons to use the drug to attack a weight problem before it becomes diabetes—a process that takes time as your body becomes resistant to insulin. In 2012, the United States healthcare system spent $245 billion dollars on diabetes. Some researchers estimate this cost could rise to $512 billion by 2021. Effective weight-loss drugs could help stem that bleed.

Still, why use a drug at all when most physicians say people can beat their weight problems on their own? "Virtually 100 percent of people can lose weight and do it successfully," Marc Reitman, a doctor and scientist at the National Institutes of Health (NIH) in Bethesda, Maryland. The problem—as if I really need to spell it out—is keeping that weight off. Reitman notes that the five-year failure rate for weight loss is amazingly high.

Your body fights you when you diet. "Your brain thinks you are starving," Reitman says, and you adapt to the reduced calorie intake. "In response, you feel hungry and your metabolism becomes more efficient," he says. That’s why diets must last for life, and "that’s not a message everybody wants to hear," Reitman says.

Though it is one people should listen to. If you want to add a drug to your weight loss plan, you’ll need to consider the risks. "Every drug has a risk," says Reitman. Liraglutide might not give you tumors, but it will drive up your monthly premium.

1 UPDATE: 4/20/2016 3pm ET This article has been updated to fix a currency conversion error. Previously, this sentence said liraglutide had earned Novo Nordisk $23 billion in 2015. That value was meant to be listed in Danish Krone (23 billion of those equal roughly $3.5 billion US dollars). Sorry for the confusion.