Skip trying to simply sweat off the pounds with saunas and sweat suits. For true, lasting weight loss, instead keep your focus on a consistent, balanced workout plan and a healthy diet with the right caloric deficit.
I'm thinking about training for a marathon. A marathon is 26.2 miles or 42 kilometers. Although some marathons differ in their terrain (some are very flat, some are extremely hilly) and degree of difficulty, the distance is always 26.2 miles. Races that are shorter or longer in distance have different names (such as 5K, 10K, half-marathon, or ultra-marathon).
For most runners, this distance will be 20-23 miles......the long run range that most experts consider to be optimum for marathon training. It's long enough to challenge and develop your body and to accustom you to the time you will be on the course in the race. I don't think longer runs are any more beneficial.