Running

Longer at a slower pace. Weight loss - then weight management - is a long term project, so start as you mean to go on. Doing the majority of your running at an easy pace, even once you're experienced and used to doing harder sessions, is the best way to slowly and sensibly build running muscle, and get joints and tendons strong and more injury-resistant. The biggest risk with trying to run every run faster is that you over-stress all these things, causing greater injury risk. Which means (a) you can't train, and (b) you're more likely to get put off keeping it going as a long term habit.