How can a 13 year old girl loose 25 pounds FAST?

Losing weight rapdily is unsafe and almost always results in a weight gain equal or greater to the amount that was originally lost. The best - and safest - way to lose weight is to diet and exercise. Never go below 1,200 calories a day, and focus on healthy foods like fruits, veg, whole grains, meat, and dairy. Try to avoid fast food, soda, juice, candy, added sugars, and processed foods. Moderate exercise is also great to help tone muscle and lose fat.