In simple terms, regular running can contribute towards weight loss but it won't necessarily achieve it upon its own, particularly if one's diet isn't set up to support such an aim.
However, upon the assumption that one's diet is set up to support, although running will improve one's fitness, it's largely the intensity (not so much the length) of the endeavour that leads to the greatest levels of weight loss.
Regardless of whether they race or run recreationally, the vast majority of regular runners will incorporate steady, fast and long runs into their training schedules.
However, despite being shorter in length, it's the higher tempo runs that yield the greatest levels of weight loss, largely due to the number of physiological changes that occur within the body throughout the endeavour, due to the fact that tempo runs take place at close to the anaerobic threshold level.
However, before attempting tempo runs, a decent level of running fitness (stamina) should have been developed through steady paced/slow runs.
While longer runs will aim to improve endurance, they don't have the same effect upon weight loss as speed sessions, since longer runs use the body's aerobic system. That said, they’re still an effective piece of the running jigsaw puzzle, so don’t dismiss them if running is something that you’re considering.
Moreover, by incorporating all three techniques, in addition to benefitting one another, their incorporation allows you to become a more seasoned runner.
Most importantly, don’t neglect strength training for your legs and core, as your muscles need to be sufficiently conditioned for the rigours that running places upon them, in order to avoid injuries.
