I need to lose 20lbs fast

Watch your carbs intake - eat lots of protein - drink lots of water and exercise.

i used to be really big i kept eating tomatoe sandwhiches and i got skinny quick.

It may not work for everyone, but I've noticed certain foods I was eating seemed to put on more weight. I lost about 60 lbs in about six months (maybe less) by cutting down on the amount of dairy and pasta I was eating. I also started going for portion control and getting more physical activity. I've got a bit of a caffeine thing (and a carbonated pop thing), so I switched to diet pop -- way less calories!

A friend also recommended http://www.everydayhealth.com to me as a way to track what I was eating and find healthy recipes -- between exercising and being healthy, I've gone from being big all my life to being about 25 lbs overweight at this point. The sad thing? The best thing for me was to actually eat out more. We eat a lot of meals as a family that aren't healthy, so the healthiest thing I could do was to stop eating meals with the family as I was unsuccessful in getting them to change their habits. Although now they're considering it.

I did the low carb diet and in 2 weeks I ended up losing 15 lbs. I stayed on it for about another month and ended up losing a total of 38 lbs....

Power Walking is the best way to lose weight quickly, even without dieting too much.  A reduction in calories will help to lose more quickly, but if you walk at least 4 times a week for 45 min to an hour, you will see results in a very short time.

Well, there's no way to lose WEIGHT mega fast, but if you want to speed it up a little, try cutting back carbs to maybe no more than 30 grams a day and tone your muscles (toning burns fat more quickly). Drink one glass of water before and after each meal and eat portion sizes. If you slow down, you won't feel as empty. Just remember: it takes 20 minutes for your body to recognize how much food is in your stomach. Hope I helped!