I've been doing 100-150 sit ups for 3-4 months and have no results...Y?

Well, with a BMI of 20, you must be extremely skinny. So although you don't have much fat, or even none, around your mid section, this also means you don't have very much muscle mass.

Most people have to cut fat to get a six pack, it sounds like you don't. You need to build muscle. More abdominal muscle.

Don't do them everyday, muscles take time to repair themselves and grow back bigger and stronger. 3x per week is the most you would want to do. Switch up your routine every 2 - 3 weeks, try adding weight to your chest to put more stress on your core muscles during crunches.

To grow muscles, you need to eat additional calories, and extra protein. Without that, you won't grow, period.

For upper body, do push ups, vary your hand width every set.

Do

20 really wide hand width

20 medium

20 narrow with hands almost touching

Also do some clap push ups to add power and explosiveness to your chest. Do this every third day

For your back you can do pull ups on a bar, if you don't have one, go to a grade school park and use the monkey bars. Do 3 sets, as many as you can do each set. Then rest for 5 minutes, then do 2 more sets where you hold yourself at the top flexed position as long as you can and slowly lower yourself down.

GOOD LUCK!

First off, I'd make sure you're doing the sit-ups right. A lot of people (like me) use their hip flexors when doing normal sit-ups. Try using a machine or something. Next, I'd make sure that you do lots of cardio to burn off calories. If you only do sit-ups and nothing else, you'll likely do nothing. Calories that aren't used will simply turn into fat. While some people develope muscle BENEATH their muscles (making it so they have a six-pack but are still overweight), others develope the fat OVER the muscles. So, like I said, do cardio and make sure you aren't using your hip flexors.

doing sit ups inst the only way to achieve a six back. everyone is different. try going on a run, you have strong abs if you have been doing this everyday but there is just some bodyfat covering them up, go on a run or do some other cardio, doing sit ups isnt as good for burning stomach fat as running is. once you lose this stomach fat youll be able to see youre abs

Chin ups are really good for upper body strength..

make you excercises interesting, listen to music, get you friends maybe to help you..

you could also go to the gym and ask for someone to test you on your fitness, and they could help you reach your goal..

ALSO NB: to see if your doing the exercises properly.. if not done right you could be doing yourself more harm than good.. seriously go to a professional, let them see you doing your exercises.. they might have a few you might want to try..

:) best of luck

First of all, in case you are not wasting any weight you would be gaining muscle. Try consuming much less meat/ fitting vegetarian, after which carrying on with your undertaking time table. (I believe it is pleasant!) A well technique to burn energy, as unusual as it sort of feels, is "frog jumps" or "squat jumps". Jump up, and squat down, and leap again up once more... Lol! Good good fortune!!!