How to lose 40 pounds in 4 months for teenage girl that is 5 feet weighs 165 ?

You change...: ...Your habits. You get fat with a bad diet and bad habits. You get thinner by changing that. Eat six small meals instead of 2-3 large ones. Always eat breakfast. Avoid fatty/fried/sugar (including too much fruit). Exercise. 40lbs in 4 months amounts to about 2.5lbs per week, which is highly doable, but only by changing habits. There are no pills. There are no shortcuts. Good luck.

Weight loss: Diet and exercise is the best. Do not look to meds for the solution. Consider eliminating soda, desserts and any late night eating.

Unrealistic: Permanent weight loss is most likely when you make a permanent change in lifestyle and that leads to about 1lb/wk in weight loss. Rapid losses whatever the plan are usually met by rapid gains. Get on a program that increases your exercise and decreases your intake and this can be sustained. If not, just learn to live with it.You can lose the same 20 lb 50 times and remain miserable.