If I do gym exercises only for my abdomen, will it affect other parts of my body like biceps, triceps, etc?
It is absolutely impossible to eliminate body fat in "only one place".
Lifting weights has no connection to eliminating body fat. Lifting weights makes your muscles larger (which is totally fantastic) but has no connection to eliminating body fat.
The only way to eliminate body fat is via diet. Body fat is simply caused by eating carbohydrates, which triggers your pancreas to cause glycerides (always present in your bloodstream) to pass in to fat cells in your body (becoming triglycerides). It's just that simple.
(If you grab your gut and feel "flab," that is just fat cells, blown up like balloons, with triglycerides inside them.)
To eliminate body fat just slash carbohydrate intake. You might say "OK, I'll eat zero carbohydrates" but that simply won't work (it's simply impossible to have that much willpower). You have to eat the "Goldilocks" amount of carbohydrates (about 70 grams a day) ..... not too little, not too much.
Note that in the modern diet (for the last few hundred years) people eat incredibly more carbohydrates than this amount each day, so for a week you will feel you are eating strangely, then you will feel in perfect health (and easily eliminate body fat each week).
Absolutely no willpower is required. The only reason people have hunger, and "want to" eat more than they need to (why would your body possibly make you want to do that?) is because they eat incredibly high daily amounts of carbohydrates.
Regarding aerobic exercise (jogging). (i) if you do a really tremendous amount of jogging (say one to two hours a day) that will use a very small amount of calories - i.e., you will be able to additionally eat a small amount of food equal to "that many" calories. however (ii) exercise makes you hungry (far, far, far in excess of the "amount of calories extra you can eat"...) so exercise is pointless if your aim, as such, is to eliminate body fat.
Here's one of many books that explains concisely the above (well, the above is more concise :) )
If you want to lose fat around your belly, there are only 2 "real" solutions:
- Go to a health clinic and get rid of the fat surgically but I wouldn't recommend that.
- Do sports and lose fat on your whole body. The human body doesn't allow you to lose fat somewhere specifically.
There are tons of article on the web which promise you will lose belly fat. I would guess 99% of these are either crap or will help you "only" to lose fat in general. A nice general article is on wikihow: http://www.wikihow.com/Lose-Belly-Fat
The basic principle is to eat healthy, sleep enough, drink enough water, and do sports, and most importantly keep doing it! You will lose fat, get healthier and (perhaps) live happier. But please don't expect to only get rid of your belly fat and that it will happen quickly. You need time and unfortunately hard work to get in shape.
Also, when losing weight, it's not important if you go to a gym, train at home, if you jog, swim, walk, ride the bicycle, or go dancing. Just do it (long enough), have fun and stay motivated.
Oh, and if you never did some sport or you are totally out of shape, please visit first a doctor or a good instructor before you damage your body.
You basically have two questions. First, it is mostly possible to exercise only your abdomen, although one might ask why you would want to. If you only do abdomen exercises, you'll only really be working that area and a few supporting muscles. You're better off working more parts of your body, honestly. The variety will help you be less bored and, unless you're bodybuilding, the difference in mass is not going to be evident in any significant way.
Secondly, you can't target fat loss in any significant manner. There has been some research showing that high-intensity exercise in a given area slightly increases the shrinking of fat cells in that area, but it's a fraction of a percent, so it really only applies in the lab. That said, losing weight is very possible and doesn't require an extremely strict diet. Frankly, what is proven over and over again from a science perspective is that pretty much any diet works as long as you stick with it with the caveat that no diet works if you don't. The two simplest diets I know of are a) simply counting calories and going below what you need per day. It's a nice simple mathematical model, but is difficult if you're not the sort of person who likes to do the math and keep track of it. An even simpler one? Eat more vegetables than fruits. Eat more fruits than grains. Eat more grains than meat. Eat more meat than sweets and oils. If you do that, and add a little bit of exercise, the odds are excellent that you'll be getting enough nutrition and not too many calories.