stomach is your problem area. It's where your body stores food in case of famine. Everyone has such an area. You probably did some sit-ups or such, so you have some muscles on your upper abs. And you have less muscle on your lower abs. So, your body stores fat in your problem area, and first in the lower abs, where there is a lot of space for it (little to know muscle). Then on the upper abs, where there are some more muscles underneath, and so you have less fat there.
It's all genetic.
jogging is an excellent exercise because it let you lose weight
evenly throughout your whole body. If you want to lose weight in
specific areas, you should target them with exercises. If they are
your problem areas, they will be very difficult to tone. You will have
to work double on them. The best approach is this:
1. Lower/control your daily calorie intake (control for normal
weight, lower for overweight).
2. Run/jog to lower your overall body fat percentage.
3. Target your problem areas with exercises.
an excellent exercise you can do it at home in front of your TV:
Attach a couple of ankle weights to your ankles.
Lay down on the floor or any other hard
surface. Use an exercise rug so as not to bruise your spine off the
floor. Put your hands behind your head, or spread them wide. Lift
your legs perpendicular to the floor, stop for a second. Lower the
legs down. Repeat ten times, stop. Turn on your stomach, raise on
your hands, with the lower part of the body on the floor, as if
trying to look at the ceiling. Turn back, do another set. Do three
sets with ten repetitions every day. In a week, you should see the
results. Once you are used to the exercise, and your muscles won't
get stronger anymore, add weight to your ankle weights. Remember:
repeating the same easy exercise many times won't help. Do it only
with the weights. Simple leg raises do not work. Use weights,
they do wonders. Stretch your spine between repetitions. Be careful
not to go for too heavy weight at once. Do not increase the weights
continuously, stop when your abs are defined - too heavy weights
will lead to injuries.