At 5 feet 11 inches and with a weight that rises and falls from 230 to 286 pounds, Pitkanen has a body mass index well over 30, the cutoff used by many to determine obesity. Although he said he had “naturally always been heavy,” he sometimes gains more weight before a trek to ensure he is still considered obese when he finishes.

Pitkanen is the first to admit that his regimen is unusual. He said he visited a doctor at least every two weeks. His physicians discouraged him from gaining more weight and yo-yo dieting, he said. But by completing the multiple-day competitions as an obese athlete, he is doing a small part in changing the perception of overweight athletes, doctors said, although most physicians have long warned that obesity can lead to an array of health problems, including diabetes, high blood pressure and heart disease.

“Fat doesn’t play as much of a role in fitness as people think,” said Dr. Linda Bacon, a physiologist and member of the National Association to Advance Fat Acceptance. “Some people who are really fat exercise regularly. We see top athletes perform well in fat bodies. Times are changing. The population has gotten bigger, so we’re going to see more fat athletes out there.”

Bacon said physical activity was important to good health but might not necessarily equate with weight loss. “Exercise is the greatest thing you can do for your body,” she said. “But you can be fit and still be fat.”

While Pitkanen is obese by most measures, he is not considered morbidly obese, and he may have developed strong muscles over the years, said Dr. Nada Abumrad, an obesity researcher at the Washington University School of Medicine in St. Louis. “I’m not saying it’s recommended, but there is some evidence that if you are obese, your muscles have to adapt to carrying the extra weight.”