Hi, I'm looking into doing this as I work from home and don't get out much, and I just feel like a hamster in a wheel if I use the treadmill at the gym. However I am very large (nearly 18stone) and would appreciate any advice from the larger (or formerly large!) members of the forum before I go headlong into this. Would you advise attempting to lose more weight first? I can walk, swim and crosstrain (and generally do low-impact stuff) for ages, but my knees aren't used to running and I'm worried as to how my bodyweight might affect them (yes, I will also be speaking to a doctor). I do at least have some nice flat routes nearby which is a bonus Thanks!