A major new paper appearing in today's edition of the Journal of the American Medical Association finds that childhood obesity -- age 2 to 5 -- has fallen from 13.9 percent in 2003-04 to 8.4 percent in 2011-12. This age (represented by dark green in the above chart) was the only group to see a significant decline, but it's generating headlines because it raises hopes that these children will remain at healthy weights as they get older. It won't surprise anyone to say that the nation's obesity epidemic poses a major public health problem.

The new paper, by Centers for Disease Control researcher Cynthia L. Ogden and co-authors, doesn't say why childhood obesity is declining. But the paper and several other studies that it cites suggest a number of theories:

  1. Nutrition assistance such as food stamps and WIC (women, infants and children) may have led to decreases in childhood obesity among low-income Americans as federal standards have changed to promote healthier eating. For example, WIC has revised its funding formula to boost the amount of fruits and vegetables and peanut butter a mother and her child eat. At the time time, WIC has limited the amount of (non-breast) milk that a child drinks, to limit fat intake.
  2. New federal nutritional guidelines have trickled down to state and local programs, such as encouraging increased consumption of water and 100 percent fruit juice, limiting serving sizes, encouraging a single adult not to feed more than one infant at a time, and limiting time in front of the television.
  3. As the value of breastfeeding has been increasingly understood, there’s been a substantial increase in babies drinking breastmilk. One study showed that 70.3 percent of children breastfed in 2000, rising to 74.6 percent in 2008.
  4. Pregnant women have increasingly understood the risks of smoking during pregnancy, with a study showing the percentage of women doing so declining from 13.3 percent in 2000 to 12.3 percent in 2010.
  5. Food companies, under pressure, have limited television advertisements targeting children. Between 2003 and 2007, the daily exposure of a child, age to 2 to 5, to food ads fell by 13.7 percent.
  6. A number of national initiatives have promoted healthy eating among children, such as first lady Michelle Obama’s “Let’s Move” initiative and reports from a wide range of groups such as the American Public Health Association and American Academy of Pediatrics