Dr. Oz says most girls do not show signs of puberty until they are at least 8 years old, but being overweight could start the process a little earlier. "We think that what happens when you get heavy, the fat comes alive and it actually takes the hormones in your body and starts converting them to estrogen, which is what actually starts the puberty process," Dr. Oz says. "The other thing that happens is you get more insulin. Most folks don't realize what insulin does besides the fact it controls blood sugar. … Insulin is an anabolic hormone. It builds you," he says.
Although other environmental factors could contribute to early puberty, Dr. Oz says being overweight is the most common cause. "The first thing I'd start out with is tell her to go outside and play," he says. "We can talk about foods and all those things, but the number one thing that little kids need to be able to do is go outside and do the things that historically humans have always done, which is expend energy by playing and having a good time."