It is not possible for a diet to focus only on your fat thighs or flabby triceps and reduce fat in these areas only.
When you really lose fat, it will be from all areas of the body and not from a single or a few areas only. This same principle also applies in case of belly fat too but still you can do something about that area.
What you can do is that you can do targeted physical training exercises as part of your daily routine and the muscles in that area can get toned and better support your body.
When you do abdominal exercises, it makes your abdominal muscles tighter and firmer and this means a better posture for you. By doing this you can give a flattened look to your stomach and people will take it as weight loss because of the better posture you have been able to achieve with improvements in your muscles at belly.
Similarly you can make your triceps area look better by doing triceps muscles exercises to strengthen these. It will look better even without loss of body fat.
And by doing regular physical training you tend to loose fat through out the body and the areas particular under your focus will show more improvement in appearance even when there is a layer of body fat under the muscles in that area.
Even by having the best muscles in the world, you can now show them if these are covered under thick layers of fats. So the overall body fat loss is most important.
The message is very clear that it is not possible to get the rock hard abs from the abdominal exercises machines that are all the rage on media for so long now. True that by doing these exercises your body can better support your posture because of strengthened muscles but there is not way in the world that you can get in shape without reducing fat in your body.
This physical training burns fats in the body and you will notice that any good weight loss program will also recommend certain diet along with this training because only by following these dietary recommendations and by altering your eating habits, you can bring the biggest influence to your body shape. Exercise equipment alone can not achieve this.