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Making Your Body Work for You

“Am I normal?” That's a question many girls ask during puberty. Chances are your body development is quite normal. But there’s so much going on at once, just knowing what's coming can help put your mind at ease. Here's what to expect during puberty -- and why.

Intro to Puberty

Puberty usually starts between the ages of 8 and 13 and lasts a few years. It may start earlier in girls who are overweight, or later in girls who are very athletic or thin. If you are 12 and haven't started developing breasts or are 15 and haven't gotten your period, your doctor will probably want to examine you to make sure everything's OK.

During puberty, your body releases hormones that stimulate your ovaries to start producing the female hormone estrogen. Gradually, a girl's body starts changing into a woman's body. But these surging hormones can also make your mood go up and down -- and sometimes it may seem as if your body is out of control.

Growing and Gaining Weight

Most girls experience growth spurts early in puberty, while most boys have them later in puberty. That’s why many girls are taller than boys in middle school.

Increased body fat is also a normal part of puberty. “You may go from 8% to 21% body fat,” says Kathy McCoy, MD, a psychiatrist who co-wrote The Teenage Body Book and who was a columnist for Seventeen magazine.

Don’t go on a diet to try to lose this weight. "It’s not bad fat," says Melisa Holmes, MD, who co-wrote the Girlology book series. "Women just have to have a certain amount of body fat for reproduction and the health of our menstrual cycles.”

Breast Development

Along with gaining curvier hips, your breasts grow during puberty. Inside them, a network of milk ducts develops. This is your body's way of preparing you to nurse a baby when you're older.

Breast development is one of the changes that stress girls out the most. Many girls worry that their breasts aren’t growing enough. But breasts usually continue to grow until you’re 17 or 18 years old -- or even into your 20s. Sometimes one breast grows faster than the other, although the slower one usually catches up.

Your nipples also change during puberty. They can become pink or dark brown, turned inward or out. Sometimes hairs grow around them. All of this is normal.

If you want to get an idea about what your breasts might look like as a woman, look at your mom. Your final breast size is based partly on heredity. “Your breasts aren’t necessarily going to be the same as your mom’s because you’ve got your dad’s genes added in, but you can look back at your ancestors and get a pretty good feel for it,” Holmes says.

Girl to Woman: Your Changing Body

Teen girls: See how your body changes during puberty.
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