Five specialists in obesity came together at Cambridge’s Royal Sonesta Hotel on Friday for a forum called “Why Is Weight Loss So Hard?” The event was part of the four-day Blackburn Course in Obesity Medicine, sponsored by Harvard Medical School (HMS) and Massachusetts General Hospital (MGH), during which experts from across the globe gathered to discuss one of America’s fastest-growing and most important health issues — the country’s increasing levels of obesity.Complex causesThe panelists agreed on the complexity and interacting issues that underlie the crisis. Genetics and environment are just two of the many factors involved.“The world is getting heavier,” said moderator-panelist Lee M. Kaplan, an associate professor at HMS and director of the MGH Weight Center, “and this is not a personal problem of slovenliness or laziness by the patient.”Nadia Ahmad, former HMS instructor of medicine, now director of the Dubai Obesity Medicine Center, agreed: “There’s a lot of research to show obesity is actually a biological problem,” she said.The causes and consequences of obesity are different in every case, Kaplan said. “Obesity isn’t the same disease in everybody. Our bodies have 20,000 genes and 4,000 are involved in weight regulation.”W. Scott Butsch, an instructor of medicine at HMS and a doctor at MGH, and Caroline Apovian, an associate professor of medicine and pediatrics at Boston University School of Medicine, pointed to the roles of age and gender.“As we get older our bodies change: We gain fat and lose muscle mass, which can impact health,” said Butsch.Apovian moved from the physical — “men and women are very different about where they distribute weight” — to the psychological. Additional social pressure on women to be thin, she said, “can create psychological issues” as well as weight issues.Environmental factorsIncreases in obesity stem in part from “all the prescription medications that cause weight gain,” said Louis Aronne, clinical professor of medicine at Weill Cornell Medical College. In addition, today’s stressed person “sleeps an hour less today than 100 years ago.”Ahmad said, “The obesity epidemic is absolutely environmentally driven,” pointing to “more processed food and people working longer hours.” Kaplan described all these factors as “a perfect storm” pushing obesity: “We work too hard; we play too little; we eat too much; our circadian rhythms are disrupted; there have been big changes in our food.” It all adds up to more weight.Can we change our environment and lifestyle to reduce obesity? Lifestyle changes in isolation have little chance of fixing the problem, Ahmad said. “Just getting rid of sugar-sweetened beverages won’t work,” she said. We need to make better food choices, but also “reduce stress and promote more sleep,” she continued.Kaplan agreed that there’s no “one-size fits all” remedy, but “we can decide what we eat and how much we exercise and the amount of sleep we get and how much stress we have.”Weight managementPrescribing a weight-management program is maddeningly complex and highly individualized, said Aronne. “In some cases, it’s just trial and error.”Diets don’t have a great track record, the panelists agreed. “No one diet has been shown to cause more weight loss than any other diet,” said Kaplan. Physicians and researchers have to do more to address the obesity epidemic, he said: “We need to do a lot more with research, with community-based care,” and other treatment options.Ahmad was optimistic that more treatments are in the pipeline: “We’re going to have more drugs and treatments, but what you do in your lifestyle” is important too, she emphasized.