Now one Van Nuys doctor believes fighting obesity has to begin by setting a good example, and she's taking her own advice.
Eighteen-year-old Michelle Delgado and her younger sister have been struggling with weight all their lives.
"I don't feel comfortable being teased by some kids at school so I just need to lose weight so they can stop teasing me," said 15-year-old Jessica Delgado.
For the first time in their lives, the sisters have lost about 10 pounds with the help of their new pediatrician, Dr. Janesri de Silva, at Northridge Hospital Medical Center.
Dr. De Silva says you just can't tell patients how to lose weight, you have to show them. She has lost 35 pounds and she's getting her patients' attention.
"I'm not going to tell you to do something that I can't do so I'm going to do it with you," said Dr. De Silva, a pediatrician at Northridge Hospital Medical Center.
Dr. De Silva says a good doctor understands the challenges that his or her patients go through. They offer advice that they would follow themselves and give support.
She runs three practices and works 12 hours a day, but she finds time to exercise every day.
"If I can fit in that hour a day, then they can too," said Dr. De Silva. "They need to get out there and play. They need to do fun things every single day and that is also going to change their lives."
Besides asking her patients to limit fast food, treats and sugary drinks, she says focus on getting five to seven servings of fruits and veggies a day. She advises kids to have a glass of water and a piece of fruit before every meal because it can help keep their portions under control.
Dr. De Silva says parents also have to lead by example.