Tom Hughes wants to change the way you think about obesity.
As the chief executive officer of Zafgen, a company developing a weight-loss medicine that went public in June, he has reason to. But he argues the evidence just doesn't stack up to support the idea that diet and exercise can effectively reverse obesity.
"Treating obesity with dietary prevention and exercise is like putting sunscreen on melanoma. It's too late," Hughes told CNBC. "People who have established obesity, they will need treatments, they will need care to get out of that, and unless we wake up to that fact and understand and research what is at the heart of that problem, we're not going to have an answer."
Hughes noted that diet and exercise have shown in dozens of studies to help people lose about 3 to 5 percent of their body weight in the course of a year.
"That's about it," he said. "For somebody who needs to lose 100 pounds, that's more like 30 percent weight loss, and we know that diet and exercise are really out of that reach."
Last year, the American Medical Association, the largest physician group in the U.S., officially recognized obesity as a disease "requiring a range of medical interventions to advance obesity treatment and prevention."
And it's a large problem; more than a third of U.S. adults, or 79 million people, are obese, according to the Centers for Disease Control and Prevention. Obesity is linked to higher rates of heart disease, diabetes, stroke and some types of cancer, "some of the leading causes of preventable death," according to the CDC.
Yet it's been an uphill battle for developers of obesity treatments. Two years ago, Arena Pharmaceuticals and Vivus got approval for the first new obesity drugs to market in the U.S. in 13 years, and a third new drug, from Orexigen Therapeutics, is now under review at the Food and Drug Administration.
The area had been plagued by safety concerns, including the withdrawal of some drugs like fen-phen, a combination of drugs that was pulled from the market in 1997 after it was linked to heart-valve problems, and Abbott Laboratories' Meridia, which was taken off U.S. shelves in 2010 after it was tied to heart attacks and strokes.
"There was a lot of investor and physician excitement in the space" around the new drugs, Jason Butler, an analyst with JMP Securities, said. "What we've seen commercially since two of these drugs have been launched is, somewhat disappointingly, adoption really hasn't been there."
Butler cited caution among physicians to prescribe drugs for obesity, given past safety and efficacy issues. He also noted initial difficulties with reimbursement and a lack of resources among companies taking the drugs to market. Arena is now partnered with drugmaker Eisai, while Orexigen is working with Takeda Pharmaceutical Company, both of which are expected to put more marketing muscle behind the medicines.
Zafgen's compound, beloranib, is in mid-stage trials in obesity and is also in testing for a rare disease called Prader-Willi Syndrome, a genetic disorder characterized by an uncontrollable drive to eat. It works in a different way from the other three medicines, which aim to reduce appetite; "it works to really impact the way that the body handles fat," Hughes said.
He added that one of the biggest hurdles facing obesity drugs is a bias against treating obesity as a disease, something he believes needs to change.
"In general over the years, people have regarded obesity as a problem of the patient," Hughes said, "that it's their responsibility for becoming obese and it's their responsibility to become lean again, as if that works."
—By CNBC's Meg Tirrell.