When the American Medical Association classified obesity as a disease, Nikhil Dhurandhar, a researcher and vice president of The Obesity Society, said he welcomed the news as an acknowledgment of the challenges people face fighting the battle of the bulge. But he wondered if the declaration went far enough.
Like a growing number of experts, Dhurandhar believes the accumulation of excess fat is likely to have multiple causes beyond a potato-chip-and-couch-potato lifestyle.
Dhurandhar likens obesity to other chronic diseases. Just as the term cancer covers the numerous conditions that occur when abnormal cells divide out of control, obesity may not be a single disease but rather, a group of diseases tied together by the symptom of too much body fat, he said.
"It may look the same on the outside, but what triggers the condition varies from person to person and may require a different treatment to control," he said. "Down the road, we need to figure out why people become fat and then tailor their treatment to address the underlying causes."
Dhurandhar's own studies at Pennington Biomedical Research in Baton Rouge, La., focus on obesity-causing viruses. He discovered the viruses in chickens back in the 1980s and has since associated the presence of certain viral antibodies in the bloodstream of humans to increased body weight.
In one of his landmark studies of 500 people, 30 percent of the obese patients tested positive for the virus, compared to only 11 percent of the lean individuals.
Dhurandhar is quick to point out that he doesn't believe most obesity is infectious in nature, but said that the discovery of a "fat bug" should be a wakeup call to researchers, physicians and anyone struggling with their weight that there may be more to shedding surplus pounds than simply cutting back on calories and putting in a few extra treadmill sessions.
"What good does a starvation diet do if obesity is caused by a virus?" he asked.
Beyond viruses, scientists have identified at least 84 other potential contributors to obesity, Dhurandhar said. They range from genetic to biological to psychological to environmental. Currently, there are about a dozen of these obesogenic culprits under serious study in labs around the world, he noted.
For example, numerous studies now associate lack of sleep with an expanded waistline. Other studies have found that exposure to certain insecticides and plastics disrupt gut bacteria, which may stimulate appetite, slow digestion and accelerate fat storage. And some studies propose a link between the lifestyle habits of great grandparents and their great grandchildren's weight status.
"Not all the causes will wind up being treatable or preventable -- you can't do anything about what your great grandparents ate -- so we will have to focus our efforts on the ones we can control," Dhurandhar said.
Christopher Ochner, director of research development and administration at the Mt. Sinai School of Medicine in New York said he agreed with Dhurandhar's idea that there could be multiple contributors to obesity, but said it complicates matters to classify obesity as multiple diseases.
"At the end of the day, we still have the law of energy balance to contend with," he said. "If you ingest more than you expend you are going to gain weight, period."
Dhurandhar conceded that eating and exercise play a significant role in obesity, but said that role is not as well understood as the general public thinks.
"We've focused almost all our resources on the so-called 'Big Two' of diet and exercise for more than 50 years and it hasn't helped," he said. "We will have to move beyond 'eat less and move more' if we want to make progress."
Ochner said he agreed that trying to lose weight and keep it off in the long term by exercising and cutting back on calories has less than a 1 percent chance of succeeding. He acknowledged that the reasons for weight gain vary greatly for each individual and the precise formula for energy balance through diet and exercise is nearly impossible to determine.
"There is literally, there is no difference between an emaciated person starving to death and an obese person on a healthy weight loss diet in terms of physiological reactions," he said. "That is going to be a tough problem to solve."
So what do you think? Do you believe obesity comes down to personal responsibility or are there other factors at play that thwart weight loss efforts? Share your thoughts in the comments section below. Better yet, voice your opinion during today's obesity tweet chat at 1 p.m., ET.
Our ABC Health tweet chat is moderated by Dr. Richard Besser, ABC News' chief health and medical correspondent. The American Medical Association, The Obesity Society and the Robert Wood Johnson Foundation are among the health groups and distinguished experts joining the conversation on this important health topic. If you'd like to join in too, click here for more details.