Why don't you read diesel's post on cutting? Really, it's not hard and these questions get to be sort of annoying to answer. I don't know one fat person that doesn't know the answer to "how do I lose weight?" (they know, but it's hard... no crap, why do you think there are so many fat people?) ok. So you're asking about your abs, not just losing weight, but in order to see your abs you need to lower your body fat percentage (work out, lose weight). Go cut. Go read the post on cutting. Now, you don't need to bench press (obvious) or do squats (obvious) and your sit ups are great. Just eat less calories than you use up and keep working on your abs. Oh yea, and I used to do a crap load of sit ups too... and well, i still do, but I found a better way, you can try this excercise.
Name - Bicycle Sit Ups
(no you don't need a bicycle)
Ok, lie back on the ground and bend your knees up towards your head sort of (don't do it uncomfortably or anything, just do it)
Ok now put ur hands on the side of ur head with ur elbows sticking out (not behind your head because then you wont get the same workout and it's not [as] hard on your abs)
Now what you do is you stick your right foot out (keeping your left knee in) and touch your right elbow to your left knee. Then you do the other side. Do this about 100 times, then you're going to be tired. Your abs will hurt for a little while, but within a minute you'll get over it. Do it very quickly (like riding a bike) so the whole thing should take like a minute or two (for all 100 sit ups) and you can do this like 3x a day. So, it's still a ****load of sit ups but it works better and is a lot more time efficient.
