Weight Gain In My 13 Year Old

I am looking for some advice. My 13 year old daughter is 5'3" and weighs about 120 lbs. She is by no means overweight. But I have noticed in the last 6 months or so that she has developed a stomach pooch and muffin top. I have noticed that many young teen girls are thin but have this problem area. Why is this? I'm not sure what is causing this. She has had her period for a while so the hormone levels should be pretty level. I try to minimize the junk food in the house and have about 90% healthy foods. She plays basketball and they practice alot so she is active with that on most days of the week. Her father and I try to set a good example. We eat healthy most of the time, whole grain, lean meat, fruits, vegetables. I run and weight train. Do you think I should get her into weight training? Is she too young? I tried to get her interested in running but she hates it. She only does what she has to to keep in condition for basketball. Her grandmother noticed the pooch also and made a comment to her. I don't want her to restrict calories to trim this down. Do I go so far as to ban all junk food in the house? 

Original Post by lcrum:

Part of my post was an observation also. I have noticed this trend in alot of girls from the ages of 25 under. Is it just because the pants are cut so low that the lower stomach is not held in? The girls are all healthy weight wise but they have this area of fat that is prominent. I was just wondering if it is our diets, the hormones and additives in food or the clothing styles that causes this? No offense is meant to anyone because I am working on this area myself.

 I think a lot of healthy women have that pooch you're talking about once puberty hits. I always thought we had more fat in that area to keep things protected. 

I personally think it's more abnormal when I see a woman with a washboard stomach and no pooch at all!