"One of the things I've noticed is that a lot of girls develop an eating disorder because they don't want criticism from their parents," said Jeanne Sager, a reporter who blogs on parenting Web site babble.com, and who, herself, suffered from an eating disorder.
"I don't think Mrs. Obama was trying to do anything harmful to her children," said Sager, but talking so openly about her daughters "makes it more or less open season" for criticism on their weight, whether they are overweight or skinny.
"Considering the disgusting things said about a teenaged Chelsea Clinton during her father's presidency -- when no one was actively discussing her body -- what does this sort of public attention do to a tween? And what greater good does it really serve for Mrs. Obama to be talking about her kids' struggle with weight?" Sager questioned in her blog.
Lyster-Mensh says the Obamas should continue to talk about healthy eating and behavior but cut out the focus on weight and especially refrain from talking about their daughters' weights.
"As a public figure, I think Mrs. Obama wanted people to be able to relate to her experiences and I'm sure she was unaware... that some of those messages could be taken in an unhealthy way," Lyster-Mensh said. "I am not a critic of the Obamas' approach to healthy behavior with their kids. I am concerned about weight-based language because it's demonstrably, scientifically not helpful."
Doctors say behavioral changes are key to guiding children to a healthy life.
"Weight is just a marker for behavior. Losing a particular amount of weight does not work well for kids," said Dr. Goutham Rao, clinical director of the Center for Pediatric Weight Management and Wellness at the Children's Hospital of Pittsburgh and author of "Child Obesity: A Parent's Guide to a Fit, Trim and Healthy Child. "
Despite the criticism against the Obamas for using their children as an example, supporters of the first lady's remarks say her intention was exactly to convey the message that critics have seized.
"The fact that she made this public, about her own... modest changes she made was exactly that -- That this is a public conversation about what we're all doing," said Dr. Judith Palfrey, president of the American Academy of Pediatrics, who was present at the event last week. "It's like a neighborhood conversation except that it's national, about how we live."
Palfrey shot down criticism that this kind of rhetoric sends the wrong message to the first daughters or that it breeds eating disorders.
"I just thought it was wonderful, a living example of all of us sharing with each other how we can live healthy lives," Palfrey said. "I didn't see it in any way doing anything except how we balance all the stresses in our lives."
Rao said giving a personal example helps convey the message better to others.
"I think it's completely appropriate she raised it and personalized it so that other mothers and fathers can relate to it," Rao said.
He added that the first lady raised an important issue by pointing out how her pediatrician went about informing her. Talking about the BMI "opens the door for discussion," Rao said.