It’s a great question! It’s possible if you are really want this, if you will work hard, then the results can come.
First step is following a diet. There are a lot diets. But you need the diet with minimum using fat. So, I can propose a Paleo Diet. This diet is easy. The products that you can to eat are meat, eggs, fish, fruits, etc. In this diet no limit for servings of food, you can don’t count calories. All food products have function not just help you to lose weight, they can clean your organism from bad substances. Because the rule is to use unprocessed food products without GMO. So, you will have healthy eating.
You could cut back on snacks and exercise more. Don’t starve yourself though, for that will instead make it harder to lose fat as your body is trying to “survive” by keeping the fat you are trying to lose. Not eating any snacks does a lot, as I have lost 10 pounds in 4 weeks or so (don’t really remember) Don’t trick yourself with eating a snack thinking “oh, it’s just one snack, what will it possibly do”, and persevere.
First and foremost, work with your physician in this endeavor and make sure you’re medically cleared to do whatever exercise it is you decide to do as well as making sure you’re following a diet that isn’t going to damage your health overall. But the bottom line and the only way to lose weight are to expend more calories than you take in. If you’re dangerously overweight (ie. your doctor thinks health problems are imminent unless you lose weight), she may put you on a medically supervised diet or direct you to someone who can. People don’t really want to hear that, they want to hear that, “you can eat as much as you want is a couch potato and as long as you avoid xyz food and/or take some kind of supplement you’ll drop weight like magic.” That’s all hype and nonsense.
You can lose 255 pounds by losing one pound a week for several years. Lose the pound by a combination of reduced eating and increased gentle exercise until your weight reaches a safer level.
Slow and steady wins the race. Enjoy each victory, one every day, one every week.
First you need to see your doctor. Your doctor is the best person to evaluate your overall health, make recommendations on physical activity, prescribe medication or propose other medical support (surgery, seeing a nutritionist, psychiatre, etc) and determine the cause of your weight gain.
Being young is certainly an advantage. You are smart to lose weight now instead of waiting.
Generally speaking you need to change your eating and activity habits in order to obtain and maintain weight loss. Begin slowly. Walking to the end of the street is a start. Avoiding pre-packaged foods and eating more fresh fruits and vegetables is always a good idea. Don’t beat yourself up if you slip up one day. Track your food and exercise.