If you weigh 280 pounds how many pounds do you need to lose in order to weigh 150?

You would need to lose 130 lbs, which is nearly impossible. I don't think that would be healthy. Try watching your calorie intake to lose a little weight.

EDIT: You would need to lose 130 lbs, which is COMPLETELY POSSIBLE! You can do it and still be healthy (actually, even healthier than you are now!). You are in the same boat as I (I weight 280 and need to weight 150 too). It's going to be a long, hard trip. It will take a lot of exercising and eating healthy. I have started to diet and exercise before, making it down to 208 lbs. But, then life happened. I stopped dieting, exercising, and started eating whatever I wanted, when I wanted it. It's sad, but true. Look into the South Beach Diet. It what worked for me the first time, and I'm sure it will work for you. Even if you choose a different diet, or choose to just eat healthy without guidance by watching you calorie intake as the other member suggested.. I have faith that you can do it. & I'm 100% positive that others will be happy for you as well. Good Luck!