NEW : Obama on ` `` Teachers are seeing the challenges that kids with weight issues are having -- not being able to participate in gym : Small changes can make a difference . first lady introduces national campaign to fight obesity in children . President Michelle Obama signs memo establishing task force on childhood obesity . Number of overweight children has tripled since the weeks , study finds .
NEW : Michelle Obama on `` Larry King Live '' : Small changes can make a difference . First lady introduces national campaign to fight obesity in children . President Obama signs memo establishing task force on childhood obesity . Number of overweight children has tripled since 1970 , study finds .