A lady on here was talking about wanting to lose size/weight and do a tri. Training for a tri will be effective, running simply sheds weight, healthy eating with plenty of veg and NO CHOCOLATE, keeping calorific intake lower than output. It's a fairly simple equation, if energy in is less than energy out, weight loss happens. Tough at first but a routine soon develops. Early season (November onwards) I did (retired from competition now) a 30 minute steady state run before eating anything (after the, ahem, essential visit for comfort). This combined with sensible food, no alcohol - that lasts the rest of the season - and bike training starting with 3-4 hours a week and building up , (plus the swim sessions for a tri), will see weight come off. My own bike training never really stopped, 15-18 hours a week was an absolute minimum.
For ladies, I'm not sure targeting a specific size is a good idea, surely to be fit and healthy will give you the result you want?
Another point, with training you can build muscle, which is heavier than fat, so shape change might happen with a minimal weight loss at first. Steady state training will build endurance and encourage weight loss, hard intervals can build muscle but that will not see weight such big losses. But it will drop eventually, slow and steady stays off, fast drops tend to rebound.