The average weight for someone at 5'6 is 118-148, so you would need to lose 112 pounds to get down to the 'normal' weight range.
Now, I would NOT recommend you lose this amount of weight "fast" as you say....that is a lot of weight to lose......and seeing as how you didn't put that all on "fast" you should not expect to take it off fast.
What you need to do is start counting your calories. Find out what your maintenance caloric intake level is (calories needed to maintain your current weight) and eat below this.
So at your weight it would be: Bodyweight(260) x 15 = 3,900 calories/day.
To lose 1 pound in 1 week, you'd have to drop 3,500 calories...which is a 500 calorie deficit a day...that means if you ate 3,400 calories/day for 1 week, you should see 1 pound of loss.
If you want to lose more weight faster, go down no lower than 1,200 calories/day.
Anything lower is crash dieting and is not going to be healthy or sustainable in the long term...chances are you will just end up putting the weight back on since you would not be implementing any long term healthy eating strategies.
Combine this diet with cardio...1 hour a day (if you want to lose as fast as possible).
I recommend to you do some running and jumping games
according to your age. You need only work
out to improve your fitness, not to lose weight.
Losing weight is a simple equation: If you burn more calories than you eat, the weight will come off. Start off by estimating how many calories you burn each day using the daily calorie needs BMI calculator kg This will give you an idea of how many calories to eat. Healthy weight loss is 1-2 pounds per week. To lose 1 pound per week you need to create a calorie deficit (burn more than you eat) of 500 calories per day. To lose 2 pounds a week, you have to double the deficit to 1000 calories per day. You can achieve this by eating less, exercising more or a combination of both.
You are in very sensitive age. So you must avoid junk foods , chocolates and all soft drinks.Don't start starving but concentrate on your calorie burn.
Here are BMI Calculator that helps you to calculate your all body fat percentage.