How can I

Question, I need to lose 20 pounds in three weeks. Would anyone recommend a diet for me to lose that weight?

That's over 6 pounds a week!  You don't say why you need to lose so much, so fast.  If a doctor gave you that advice, he should also explain how you should safely accomplish that. 

I don;t think safety is the issue here....

dude... If you are like the rest of us, you know every diet that is out there...and you have tried every diet that is out there... choose which ever worked for you in the past...nail it to the wall for 3 weeks...do as much exercise as you can.. Russ

Go to GNC and get the Whey Protein Isolate powdered
protein. It comes in vanilla or chocolate. You mix 1 scoop with 8 oz water and it contains 28 gm protein.
I practically lived on those for 2 weeks after my surgery.

The only thing I know of that made me lose that kind of weight is such short time (pre-op) was cutting all carbs out. I dropped 30 pounds (from 295 to 265) in three weeks when I became a vegan about 4 years ago. I maintained that diet for a year but that first 30 pounds was all I ever dropped.

Vandy puts you on a Carnation Instant Breakfast (No Sugar Added) diet for 8 days prior to surgery. I ended up on it for 16 days due to a screw up and not having my surgery when first scheduled.  You drink it 6 times a day, and can have clear liquids such as chicken broth in addition to the CIB. It really took the pounds off quickly and I didn;t get hungry. Of course, any diet like that needs to be discussed with you physician.  And like Russ said, exercise  (walking, jogging, etc.) in addition to the diet is a major plus to help burn the calories and lose the weight.

My Surgeon put me on the Medifast for 4 weeks and I lost about 45 pounds.  I had 5 packets a day, 1 for breakfast, 2 at lunch and the other 2 at dinner.  I could have water, herbal tea decaf black coffee and had to drink at least 64 ounces a fluids each day.  No milk, sweetners (splenda included) were allowed.  Believe it or not after the first two days, I was never really hungry, unless I was late for lunch due to work.

Jim 

If you can do that with out passing out please pass it on. You're younger then me but,, I am sure you could do it quicker then me but, if you can I it would be the healthiest method..  Whats the rush??