Correction appended, May 15, 2014
There's a growing mountain of evidence that obesity and other health factors can be determined as early as your time in the womb. While research has shown that too much weight gain during pregnancy can lead to an obese child, new research shows that too little weight gain can be a nearly equally risky factor in childhood obesity.
Researchers studied the electronic medical records of 4,145 women who had a baby between 2007 and 2009, and reviewed the medical information of their children between ages 2 and 5. Their findings, which are published in the American Journal of Obstetrics and Gynecology, showed that women who started at a normal weight before pregnancy, but gained more than the recommended amount, were 80% more likely to have an overweight child. Women with a normal weight before pregnancy who gained less than the recommended amount were 63% more likely to have a child who became overweight or obese.
Healthy weight gain during pregnancy for normal weight women is between 25 to 35 pounds. For overweight women, the recommended weight gain is between 11 and 20 pounds, and for underweight women, it's between 28 to 40 pounds.
When looking at the group as a whole, researchers found that among the women who gained too much weight, slightly more than 20% of their children were overweight. Among women who gained too little weight, 19.5% of their kids were overweight. And for those who gained the normal amount, only 14.5% had overweight kids.
Researchers are still looking into why weight gain outside the optimal range influences obesity, but one hypothesis is that gaining too much or too little weight interferes with the child's ability to normalize energy and metabolism.
Correction: The original version of this post incorrectly stated the recommended weight gain during pregnancy. It is 25 to 35 pounds.