The only real way to know if running will help you lose weight is to try it, says Charlie Seltzer, MD, a weight loss physician and exercise physiologist based in Philadelphia, PA. “Some people can do mini-sprints for 10 minutes three times a week and get some weight loss. But you also see people who train for Ironman triathlons who don’t lose any weight, even though they’re running 50 miles a week.”