80 pounds, 3 months, doable?

no....

20 year old man shouldn't be eating 1k...I have a son that age he eats about 4k a day and loses (active job) but no exercise. Shorter than you and weighs less.

It is not realistic or healthy

No! Counterproductive- if you go too low your body will go into starvation mode and hang on to the fat. If you're exercising you need to eat sufficient nutrients.
You can lose a lot the first week or two of a diet, this is because the first thing you use are your body's glycogen stores, and these are bound up with a lot of water. I lost 16lbs my first week. But this is not sustainable, a safe and sensible weight loss is one to two pounds a week.
If you're exercising more you may actually retain some fluid in your muscles.
One thing on your side is your gender, men lose it faster than women!

So you have been overweight all your life, and you think you can reverse that in 3 months??? Can we take a moment to think logically please.

Don't you want to learn how to lose the weight in a safe sane way that you will be able to maintain????

I eat 1000 calories in 1 meal most days. I average 1600-1900 calories and have lost a little weight. I started at 285 so about where you are now.

Read these and please start thinking in the long term not just for your birthday. Good luck

If you have 75+ lbs to lose 2 lbs/week is ideal
If you have 40-75 lbs to lose 1.5 lbs/week is ideal
If you have 25-40 lbs to lose 1 lbs/week is ideal
If you have 15 -25 lbs to lose 0.5 to 1.0 lbs/week is ideal
If you have less than 15 lbs to lose 0.5 lbs/week is ideal

http://www.myfitnesspal.com/topics/show/1234699-logging-accurately-step-by-step-guide?hl=logging+step+guide

http://www.myfitnesspal.com/topics/show/1235566-so-you-re-new-here?hl=so+you're+new+here

http://www.myfitnesspal.com/topics/show/1080242-a-guide-to-get-you-started-on-your-path-to-sexypants

Not a realistic goal. You also won't be giving your skin time to adjust, which will most likely result in more loose skin then you would have if you took a slower approach.

My suggestion is you read:
http://www.myfitnesspal.com/topics/show/1080242-a-guide-to-get-you-started-on-your-path-to-sexypants
http://www.myfitnesspal.com/topics/show/976981-welcome-to-mfp-don-t-worry-there-s-cliff-notes?hl=welcome+to+MFP&page=1
http://www.myfitnesspal.com/topics/show/1234699-logging-accurately-step-by-step-guide?hl=accurate+logging+step+by+step&page=1

No, and not even healthy way to do it.

No.

3 months - so 12 weeks - at 2lb a week (maximum recommended for health weightloss) that's 24lbs. And that's assuming that you stick to your goal deficit everyday in that 3 month period.

I'm female, older, over a foot shorter and eat a lot more than you are planning to. I'm losing weight just fine.

Please read the sexy pants thread linked above, and set a healthier, realistic goal from there. If you do that you'll be well on the way to the body you want by your 20th birthday (24lbs is a lot of weight to drop), and you'll have achieved the weightloss you want, in a healthy way by the time you reach your 21st.

Actually just re-read it and it sounds like you are planning to eat between 1400 - 1500 tops. At 6' 5" that is way too low. I eat more than that and I am 5' 2.5" female.

It's great you want to lose the weight but there is not rush, better to do it slowly and healthily and you have more chance of keeping it off.

All of the above.

80lb in a YEAR is a tough but achievable goal.

But don't let this put you off... you can still loose 20lb in 3 months and that will make a big difference to the way you look and the way you feel - not only because you will be lighter and thinner but because you will know you just need to keep doing the same to reach your target.

I suggest you take the time to read the links people put up but if you want a short version:

1) Set you daily calories based on MFP's default settings for your weight loss goal - which should initially be 1-2 lb per week.

2) Exercise is your best friend. Do a bit more strength training (weight lifting) - I know CV work give you more exercise calories but you need a bit of muscle to support your body when you do the CV stuff later - plus having muscle means you burn more calories all the time. As you progress, mix up your CV and strength training. Any decent gym will give you good 1:1 advice on this. If you are training at home plenty of research so you don't hurt yourself!

3) Non scale measurements (eg clothes sizes) are more exciting than weighing in and actually quite often you find you weeks where weight stays the same and your body changes. Enjoy and share your successes here.

4) There are a million views on the best way to consume your calories (dat/carb/protein mix etc). In my, perhaps over-simplified view, if your only goal is weight loss then these ratios make virtually no difference - however in terms of health and how you feel you might want to think more about your choice. Personally I found for weight training I needed to up the amount of protein I ate post exercise or my muscles didn't bulk or recover as quickly. For running (and I guess other CV work) I needed more carbs, spread throughout the day to aid recovery. In general, the more I cook from fresh the better I feel, and the more I trust the calorie count..

Good luck.

Considering your age OP it is all context relevant...as in if you drop your weight drastically in a short time frame your skin will be saggy, you may have to get plastic surgery to get rid of the excess skin left over because of your impatience. You are young therefore have time to do this and give your body the best chance it has at getting back into shape without the negative impact of drastic fast weight loss.

As mentioned if you did it in a realistic and healthy manner you would be at an ideal weight within your early twenty's.

1-2years may seem like a long time but a lifetime of excess skin or scarring is a lot longer. Patience is key OP.

NO.

25-30 pounds is doable in that time frame given your size and age, but 80, absolutely not without removal of limbs.

Rigger