New to this, please help!

Your doctor is wrong. Dangerously so. A negative 900 (or even 900 total) is at medical starvation levels. And at NO POINT should you ever net NEGATIVE. That's essentially eating NO FOOD whatsoever. That's not a diet, that's called starvation.

If you eat a deficit - just smaller amounts (use MFP's guided goal settings to start with) you will not only lose weight, but be healthier. There is no need to starve yourself. 5 pounds a week is also very unlikely. A body will adapt to your weight loss and eventually slow down. That's okay, too.

You didn't get overweight in a few months, it won't happen to come off in a few months.

Please, please do not net -900 a day. Go to "My Home", click on "My Goals" and see what MFP puts you at for a 2 pound a week loss.

Run, do not walk, away from that idiot of a doctor. Only a complete and utter moron would suggest something like that. It is a physical impossibility. To lose 5 pounds a week you would need to be at a deficit of 2500 calories a day. Your metabolism would shut down, and you could never, EVER do it. Anything more than 2 is a virtual impossibility, at least for any thing of time. So you may want to lose 5 pounds a week. I want to have a unicorn in my garden when I wake up. That ain't happening either.

Sorry, but that's impossible to maintain and still be healthy! I'm currently watching the "when pigs fly" geico commercial and I gotta tell you it's even more impossible than a pig using a smart phone. I've only ever seen that sort of diet in cases with extremely obese people who need to lose weight to get surgery.

I went through a brief period of time where I lost about 1lb a day for a total of 15lbs in 2 weeks. I didn't do it originally for the weight loss; I was depressed and realized how much weight I was losing and wanted to see how long I could do it for. From personal experience I'll tell you that you can't maintain that. I gained 5lbs as soon as I ate a normal meal. Stick to diet and exercise and lose weight slowly and steadily. The quicker you lose it, the quicker it piles back on.

Get a new doctor; from what I can see, even google is better informed than your current one.

Hi,

Feel free to add me. What you are trying to do can be done, but it takes a deep committment and sticktoitiveness...you can do it. I did. I lost 110 lbs in about 10 mos, before my RNY Gastric bypass on 7/30/2012. I eat less than 900 calories almost every day of my life. I don't recommend that for you unless you have weight loss surgery. It puts your body in starvation mode...I'll be happy to help in any way I can. You can do it....I'm down 280lbs so far and still losing.

Hang in there,

Janine Alfke

I was reading all the reply's and realized they all come off as extremely negative(save one). We are all here to encourage and help one another, including you, so please don't take it badly. I think you just shocked everyone. While don't know if what you are suggesting is possible, I do know it is extremely unhealthy. You could make yourself really sick trying, and it isn't sustainable. Eventually you have to go back to real life and real food. You would be much better off learning to eat healthy and in moderation. Slow and steady really does win the race here hunny. We would all love to lose years of weight gain in a few weeks or months but what's the point if we sacrifice our health to do it? We are here for you for motivation and support and we arent' going anywhere to take it slow! Feel free to friend me!