Can I Lose 80 lbs. in 9 weeks?

Weight loss is not constant and it's not linear. Even if it were safe to lose so much so fast it wouldn't happen in an X pounds in Y weeks fashion, anyway. You might be able to drop 10 pounds the first week but most of it would be water from the change in your diet. You may even be able to pull off losses of 4 or 5 pounds the next few weeks but as you lose weight it gets harder and harder to create the calorie deficit needed to lose weight quickly because your now-smaller mass burns fewer calories doing the same things. There are also negative side-effects of losing so much weight so quickly. Excessive muscle loss; saggy, loose skin; hair falling out; and brittle nails are just some of the things you'd have to look forward to.

The muscle loss is the worst part of this but the part you probably won't notice. As you lose muscle, your metabolism slows slightly. That makes it harder for you to maintain your new weight and easier to put weight back on. When you do put it back on (which will invariably happen because you didn't learn to eat to maintain your lower weight while losing) it will all be fat. So then your body fat percentage will be even higher than it was before you lost the weight. Then the next time you decide to crash diet you'll lose even more muscle and the cycle will continue. Celebrity diets sell magazines, nothing else.

Don't do this to yourself. Lose weight in a healthy manner and start weight lifting to maintain your current muscle mass. You'll be much happier with how you look once you reach your goal weight and you'll stand a decent shot of actually keeping it off.

Let us math!

80 lbs divided by 9 weeks is 8.8 pounds per week.

A pound is 3500 calories, by 8.8 and divided by 7 days is 4444 calories deficit in a day.

For your stats, your TDEE with 5-6 hours of strenious exercise a week is 2978 according to scooby's calculator.

So, if you eat literally nothing and exercise a lot you will still miss the mark by approximately 26.4 pounds.

I would say not possible. (If you cannot tell, I love math.)

I have similar stats to you, 5'6", 205 pounds though I am older at 30. I eat 1600 cals a day, except 3-4 days a month where I eat maintainence. (because TOM sucks) I have my weight loss goal at 1 lb per week then use exercise to push it up between 1.5-2 lbs. This gives me good motivation to work out but if I don't manage it, I still lose something. I have lost 37 pounds in 4-5 months this way so far and I am not hungry, not denied my favourite things and not obsessed over reaching a certain number by a certain time.

There is no race to the finish. Do it healthy and keep it off for the long term.

Does that even sound credible to you? What was the source? The Onion? TMZ?

For the sake of convenience, assuming burning 3500 calories will result in a one pound weight loss, one would need to burn 4444 calories more than one consumed each day for 63 days.

(3500*80)/63

It might be possible for someone *very* obese, and preferably on a medically supervised diet, to do so, and/or someone who is training at an extreme level, but absent exceptional circumstances, I would say, "no".

Even assuming one could actually achieve a sustained 2 pounds/week loss (the rate I often see posited as the maximum recommended), one would need 40 weeks. Assuming that loss rate, 9 weeks would allow for 18 pounds lost.

My actual experience so far is that in 65 weeks (roughly) I have lost 76 pounds, with another 18 to go. If I'm lucky, I'll hit my target by Thanksgiving but that's assuming the aggressive (and unlikely) 2 pounds/week rate. New Year's is probably more realistic.

Your mileage may vary.

Come on Jessica really?
Don't you know better than this at age 20 with some higher education behind you?
Unbelievable that you actually even wonder about this.

I thought this was going to be one of those sarcastic joke threads to show how ridiculous these types of posts are - but nope, it's legitimate. Anyway...

No.

Nope. Also losing 80lbs would get you to 118lbs, which for your height is on the VERY lowest edge of your healthy weight range, borderline underweight.

No. Absolutely no.

Yeah, of course you can. On another note, I've just started sh*tting gold

Lord have mercy. No. In 9 weeks you can maybe lose 18 but even that might be difficult.