The Myth of Spot Reducing
There is no such thing as spot reducing. Any fat you lose comes off in the same proportion it's stored in your body.
For example, if you carry most of your fat weight in your hips and thighs (like most women), then the fat inhabiting those area will be the last to go. If you carry your fat weight around your waist as "love handles" (like most men), then your significant other will most likely have something to hang on to right up until the very end of the reduction process.
You can target train your abs with sit ups and crunches 'til the cows come home and you can get rock hard abs, but until you lose the layer of subcutaneous fat covering them they won't be visible.
That's why strength training is so essential.
Yes, you can lose weight through aerobic exercise and dieting, but without strength training you'll also lose lean body mass which lowers your metabolism so your body burns even less calories than when you started the diet in the first place. And strength training is the only way to reshape your body.
The most effective exercise program is one that incorporates strength training and cardiovascular training coupled with sensible low-fat eating habits.