EFFECT OF EXERCISE

Have you had a doctor look at your hormone levels and thyroid? You can be very fit but still has excess fat. Get your body fat percentage checked too. Some athletes, like wrestlers and football players, can be "heavy" but have low body fat.
Good luck!

I read on a website exercise is 10% and the other 90% is what you eat makes you lose weight, don't know of it's a fact but I can agree as I've exercised like mental and gained with eating so so and exercised and eating well and lost it.

Yep, exercise is about 20% of the equation and eating heathy is the other 80%. AND both of them together is sooooooooo important. Also, I agree with the others that you need to see if you are losing inches, because that will show that you are losing "fat" but gaining "muscle" Hope that helps ya a little.

When you exercise, you build lean muscle mass, which makes you gain weight while you are losing fat. This is good because a) you are HEALTHIER, which is the goal. The number is not the goal! And b) you are building a more sustainable weight loss regimen. Without muscle, you do not burn nearly as many calories throughout the day resting.

If you have hit a stall, you might not be eating enough calories for your exercise regimen.

Depends on the exercise. Too much cardio can cause muscle loss not gain. You need resistance/weight training to help preserve that muscle mass.

This is from an article by Tom Venuto:

Do Cardio. Don’t Over-Do It. If you’re overweight, you can sometimes get away with very low calorie diets without adverse consequences if you’re not doing tons of cardio on top of it. Endurance athletes get away with high volume training because they provide ample amounts of food to fuel it (man, those guys can EAT!) Dieters and physique competitors on the other hand, often semi-starve themselves while doing huge amounts of cardio at the same time. Exercise research says that extreme amounts of cardio during a diet can actually cause the same type of adaptive metabolic downshift as eating too little food. Fitness and figure competitors have been known to do 2 or even 3 hours of cardio a day before competitions. This kind of overtraining can be counter-productive when you look at the metabolic damage and “cardio dependency” potential. And remember, if you’re not diligent, you can out-eat almost any amount of exercise. If you’re doing upwards of an hour of cardio a day and not seeing significant fat loss, you’d better take a close look at your diet first before you rush to add more cardio.
Weight training: In the physique world, weight training is a foregone conclusion. But in the everyday world of non-athletes, weight loss = “diet,” not weight loss = “lift weights.” For Suzy soccer mom, “lift weights to lose weight” probably doesn't even compute. But weight training is so important for metabolic health and better body composition, that if you were forced to choose one or the other – cardio or weights – the weightlifting would be a NO BRAINER decision. If you have a concern about metabolic damage and you’re not weight training yet, there’s nothing else to discuss. Start pumping iron, then get back to me.
What if you have long history of starvation dieting and yo yo weight cycling?

http://www.burnthefat.com/metabolic_damage.html

and:

http://www.hussmanfitness.org/index.html - lots of good info on this site. (especially "working with the body")